A Guide To Vegetable Growing

A Guide to
Vegetable Growing
A Guide to
Vegetable Growing
Stephen Alexander,
Teagasc, Kinsealy Centre, Malahide Road, Dublin 17.
6th Edition
Contents
Introduction
Cultivation of the Soil
Plant Nutrition
Rotation
16
Weed Control
18
Pests and Diseases
19
Weather
27
Bolting
30
Plant Spacing
32
Plant Raising and Direct Drilling
36
Vegetables A-Z
43
Herbs
86
Tender and Out-of-Season Vegetables
87
Appendix
89
Vegetable Growing
The selection of fresh vegetables now available in shops and supermarkets is
probably greater than ever before. But theres a huge amount of satisfaction
to be had from growing part of the food we eat. A well managed garden or
allotment is an asset to any family and vegetable growing can rapidly develop
into an absorbing hobby.
The quantities of vegetables to grow will naturally depend on circumstances.
It can be as simple as growing a pot of parsley on your back doorstep or you can
make it as big and fancy as you like. If theres only a small area available
preference should be given to items where freshness is especially valuable such
as lettuce, herbs, spinach, parsley, peas and beans. If theres more ground add
brassicas, onions, carrots, beetroot, rhubarb and early potatoes to the mix.
It will also add interest to try out some new or unfamiliar kinds each year.
Helpful Hints
(1) Vegetables can be grown on most soils (light, medium or heavy) provided
they are well drained. Choose an open though not exposed site, where
plants can receive maximum sunlight.
(2) Crops are grown on the flat, in drills (ridges) or on raised beds (also known
as deep beds). Choose the system that suits you best. Or maybe a
combination of all three.
(3) Site perennial vegetables, such as asparagus, rhubarb, seakale, horse radish
and other crops which remain in one place for a number of years to one
side so that they do not interfere with the cultivation of annual crops.
(4) Grow the early maturing crops together so that when they are harvested
the ground may be planted with late crops. For example, early potatoes,
scallions, lettuce, spinach and radish could be followed by savoy cabbage,
winter cauliflower or late celery.
(5) Vegetables are normally either sown directly where they are to mature
(known as direct drilling) or else the seed is sown into a nursery bed or
modules (multi-celled tray) and later on the young plants (transplants) are
planted out into their final quarters. Carrots, parsnips, scallions, beetroot,
A Guide to Vegetable Growing
swedes, spinach, radish, peas and beans are usually direct drilled, while most
brassicas, lettuce, celery and courgettes are transplanted. Leeks, onions and
sweetcorn are examples of crops that can either be drilled or planted.
(6) A common mistake is to sow seed too thickly. As the seeds germinate and
the young plants come through they should not crowd each other. When
thinning out plants to their final distance this should be done when they
are still quite small. The depth to which seed should be sown will vary
depending on the size of the seed. See Table 2 in the Appendix for details.
(7) Transplanted crops are usually sown under protection (plastic tunnel,
glasshouse or garden frame) into a container of some sort. These
containers could be a seed tray, small pot or a multi-celled tray called a
module. Some of the brassicas and leeks can also be direct drilled into a
seed bed outdoors and later on transplanted out as bare root plants.
(8) A garden frame (or cold frame) is a marvellous addition to any vegetable
garden. Its a simple box like structure with a plastic or glass top that
allows you to warm the soil in early spring. If you dont possess a
glasshouse you can use frames to propagate transplants or to grow early
season crops.
(9) As there are few effective insecticides available its essential to physically
protect your crops from pest attack using fleece, nets or barriers.
(10) Keeping annual records outlining the crops grown, planting distances,
varieties, dates of sowing, transplanting or harvesting etc. will add to the
owners store of information year on year.
(11) Vegetable growing can get confusing due to the large number of
different types of vegetable that are available and the many different
ways of growing them. If you are a beginner youre better off to start
small and grow something easy like cabbage, onion sets or beetroot. Look
after them well and youll get a harvest.
Cultivation of the Soil

Thorough drainage of the soil is one of the first requisites for success in
vegetable growing. The soil must be well drained so that all surface water may
drain quickly into the subsoil within a few hours of falling. As crops are
frequently harvested right through the winter growers will often grow their
crops on drills or on raised (deep) beds to improve drainage.
Building up soil fertility and maintaining a healthy soil structure is also
important. In a well cropped vegetable garden, two and sometimes three crops
a year are taken off the same piece of ground and not only the weight of the
produce but its table quality depends on the quantity of plant food available
in the soil. The texture of very light or very heavy soil can be improved by
adding garden compost or farmyard manure to the top layers. Crops that
traditionally get additions of organic matter include potatoes, celery and leeks
but if your ground is lacking in organic matter it can be applied to any crop.
All ground which falls vacant in autumn or winter, should be dug when the
weather permits. A good rule of thumb is that if clay sticks to your spade or
boots then the ground is too wet. Ordinary digging should always be done to
the full depth of the spade, turning the soil over and burying any trash or small
weeds. Lumps should not be broken during this digging, and the surface soil
can be left quite rough in order to expose it to the influence of the frost.
If you have underlying compaction problems and youre feeling energetic you
should cultivate the ground to two spits deep also known as double digging.
This involves digging out a trench one spit (spade dept) deep, taking the soil to
the end of the plot and forking over the bottom of the trench before turning
over the soil from the adjacent spit. In double digging, opportunity should be
taken to add to the subsoil such substances as vegetable refuse, old leaves and
as much manure as can be spared. On no account should the subsoil be brought
to the surface.
The formation of a fine seed bed is of great importance, especially for the
smaller seeds such as onions. Provided we get sufficient frost, ground which has
been dug in autumn or early winter will break down to a fine tilth more easily
than that which has been left un-dug until spring. To form a seed bed fork over
the ground to a depth of about 10 cm carefully breaking all lumps, and then
rake it smooth, removing stones and unbroken lumps. The forking down should
be done only when the ground is dry, and it may be advisable to wait a day or
two between the forking and raking, to allow the soil to dry still further.
Summer cultivation consists principally in the frequent use of a hoe. It is
impossible to overestimate the benefits which plants derive from having the
soil around them shallowly stirred. Not only are weeds destroyed, but hoeing
conserves moisture in the soil and it entails less labour to destroy weeds in the
seeding stage by hoeing than to resort to hand pulling when they are mature.
The action of a hoe will also aerate the soil, thereby encouraging bugs to
release nitrogen and growth is stimulated.
Plant Nutrition
Vegetables require a number of things to grow: light, temperature, CO2, water
and nutrients. The nutrients consist of major and minor elements. Those nutrients
that a plant uses a lot of are called major elements. These are nitrogen (N),
phosphorus (P), potash (K), sulphur (S), calcium (Ca) and magnesium (Mg). Minor
or trace elements are also essential for plant growth but are only required in tiny
amounts. These include boron (B), manganese (Mn), molybdenum (Mo), copper
(Cu), zinc (Zn), iron (Fe), chlorine (Cl) and nickel (Ni).
Harvesting vegetable crops removes considerable quantities of nutrients from
the soil and hence we have to replace them to maintain good yields. A certain
amount of replenishment comes naturally from weathering of minerals and
breakdown of organic matter but the bulk of the replacement has to come from
the compost, manure or fertiliser that we add to supplement whats naturally
available. But how do we know how much to add? To work that out we need
to know whats in the soil to start with and marry that with the crop to be
grown. Normally we only concern ourselves with the three major elements that
are used is large quantities by crops: nitrogen, phosphorus and potash.
The only accurate way to find out what nutrients are in your soil is to take a
soil sample and post it off to a laboratory for analysis (see Table 3 in the
Appendix). Its also possible to purchase do it yourself kits from garden
centres which will give you a rough guide to the fertility of your soil. A sample
must be representative of the area youre testing so take about 20 sub
samples, mix them up and select about 450g for the test sample. Do not take
a sample within three months of applying fertiliser. A basic test will tell you the
pH of the soil, how much lime to add if needed, plus the phosphorus (P) and
potash (K) level. Nitrogen is not normally tested for as the amount in the soil
is very variable its natural availability depends on biological processes and is
also prone to leaching.
The results of the test are expressed in mg per litre (mg/l) of soil which is equal
to parts per million. To keep things simple from an advice point of view the
results are put into a 1-4 index system where Index 1 = very small amounts of
the nutrient and Index 4 = very large amounts of the nutrient. The general idea
is to get your soil into Index 3 this is the recommended level for optimum
8
nutrition of vegetable crops. This is equivalent to 6-10 mg/l for P and 100-150
mg/l for K; the optimum pH is around 6.5-6.8. You dont have to sample
annually once every 4-5 years is recommended.
The table below sets out the Index levels for P, K and Mg.
Index
Index
description
P mg/l
K mg/l
Mg mg/l
Response to
fertiliser
Very Low
0.0-3.0
0-50
0-25
Definite
Low
3.1-6.0
51-100
26-50
Likely
Medium
6.1-10.0
101-150
51-100
Unlikely
Excess
> 10
> 150
> 100
None
The laboratory will usually make a recommendation based on the results and
what crop is to be grown. At Index 1 and 2 relatively large amounts of nutrients
are advised to bring the soil up to Index 3. At Index 3 only maintenance
amounts are required to replace whats taken out and at Index 4 usually
nothing is advised as the levels are excessive and need to be allowed to drop
back to Index 3.
Soil sample results frequently show excessive fertiliser use by vegetable
gardeners so use fertiliser sensibly and take into account that use of organic
matter will also add N, P and K to your soil.
Soil pH
The pH of a soil is a key component of soil fertility and relates to whether a soil
is acid or alkaline. Its measured using a pH scale of 0-14 the mid-point being 7
(neutral), with any reading below indicating acidity and above denoting
alkaline conditions. Whilst most vegetables are reasonably tolerant of
variations in pH (5-8) we ideally try to keep our soil slightly acidic between 6
and 7 to ensure maximum availability of nutrients (see chart). If your soil is very
acidic you can get lock-up of certain nutrients like molybdenum whilst other
elements such as aluminium and manganese become overly available to the
extent of being toxic. At the other end of the scale very alkaline soils can reduce
9
availability of elements like iron, boron and manganese. To check what pH suits
what crop see Table 1 in the Appendix.
The natural pH of a soil will
depend on the underlying
rock formation e.g. limestone
based soils tend towards
alkalinity whilst those deriving
from shale, granite and
sandstone tend to be acidic.
Over time most soils will
naturally become more acidic
due to a number of factors
but some soils never need
liming.
To find out the pH of your ground you can purchase a test kit from a garden outlet
but for an accurate pH figure your best bet is to get it analysed in a laboratory.
The amount of lime to apply will depend on your initial pH and the type of
soil; heavy clay soils will require more lime than light sandy soils to increase the
pH by the same amount. If you get your soil tested by a laboratory they will tell
you exactly how much lime to apply to increase the pH of your soil to a set
value usually somewhere between 6.5-7.0. Typical application rates for a lot
of soils will vary between 0.5-1.0 kg per m2 but do not apply any more than
750g per m2 at any one time. If your soil is very acidic and requires a lot of lime,
spread the application over a couple of years. The form of lime that is normally
used is ground limestone. Take note that it takes several months for the lime
to react fully with the soil to effect the pH change, so plan ahead and apply in
plenty of time. Lime can be applied at any time of the year but preferably apply
over ploughed or dug ground in the winter and rotavate or fork it in during the
spring. Be careful not to over apply lime as its far easier to raise the pH than
to decrease it.
Apart from correcting acidity lime also improves the structure of the soil, and
renders the plant food contained in it more available to the crop. It can also have
an effect on disease outbreaks. For example in low pH soils brassicas are more
10
liable to attack by club root disease; if the disease is already present the advice
would be to lime the ground to pH 7.4 or greater to prevent its reappearance.
Nitrogen
Nitrogen is a key nutrient for growth and is available naturally in the soil.
However we normally supplement soil nitrogen with fertiliser nitrogen and/or
by adding organic matter. Vegetables vary in the amount of nitrogen they
require. Some of the legumes such as peas and broad beans can fix their own
nitrogen and dont require any. The following list groups vegetables into three
categories of low, medium and high users of N:
Low: swede, French bean, runner bean, carrot
Medium: broccoli, beetroot, onion, courgette, parsnip, scallion, lettuce
High: leek, spinach, rhubarb, sweetcorn, cauliflower, cabbage, celery, sprouts
The following table gives suggested nitrogen application rates for a range of
vegetables using sulphate of ammonia as the nitrogen source:
Crop
g/m2
Pea, broad bean
Carrot, radish, swede
30
Parsnip, French bean, runner bean
40
Broccoli, parsley
50
Onion, lettuce, beetroot, courgette, early potato
60
Cabbage, cflower, leek, spinach, potato, scorn
70
Celery, Brussels sprouts
90
The correct amount of nitrogen to apply will depend on a variety of factors

such as cropping history and soil type so the suggested amounts may be above
or below what is optimum for your situation. In general lighter soils require
more nitrogen than heavier soils. If you are using garden compost or farmyard
manure these materials are a nitrogen source and the above figures will need
to be adjusted downwards. At best a well rotted application of farmyard
manure applied in the spring will supply the equivalent of 30 g/m2 of sulphate
of ammonia.
11
Nitrogen is normally applied prior to sowing but can be split into 2-3
applications with the higher nitrogen demanding crops. If too much nitrogen is
applied at any one time roots can
get scorched or seeds may fail to
germinate. For example with
transplanted brassicas you would
apply half pre-planting and the rest
about a month later this is known
as topdressing. Celery would get
three equal splits at planting, 3
and 6 weeks later. Be careful when
applying nitrogen directly over crop
foliage as it can scorch the leaf if Example of excessive nitrogen application
in doubt apply it to the side of the on a swede crop resulting in growth cracks.
plant. Irrigation may be necessary
after application to reduce scorch and to activate the nitrogen.
Phosphorus
This element is important for root development, flowering, seed formation,
straw strength in cereals, crop quality and disease resistance. Its also involved in
cell division and is the carrier of energy within cells.
Potash
Potassium is used in a wide range of plant processes and hence a lot of it is needed.
Its essential for photosynthesis, starch formation, translocation of sugars and in
the development of chlorophyll but the bulk of potassium is in the cell vacuole
where it is involved with turgor and water control. It also tends to exert a
balancing effect on excessive availability to the plant of nitrogen and phosphorus.
Magnesium
There are usually plentiful supplies of magnesium in soils and shortages of this
element are unusual in vegetable crops. This is particularly the case where regular
additions of organic matter are added to the soil. Sometimes you can get an
induced magnesium shortage showing up if the root system is under performing
due perhaps to soil compaction, drought conditions or wet soils. The typical
deficiency symptoms of interveinal chlorosis occasionally occur in broccoli crops
close to harvest, but only rarely has any effect on yield. If you wish to alleviate
magnesium deficiency symptoms use a 2% foliar spray of Epsom Salts (20 g per
litre of water). Add in a couple of drops of washing up liquid to allow the spray
droplets to spread evenly on the leaf.
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Calcium
One of the commonest deficiency symptoms in vegetables of any element, apart
from nitrogen, is calcium. Its usually an induced deficiency rather that an actual
shortage of calcium in the soil. Calcium is not a very
mobile element within the plant and if the
transpirational stream in the plant is interrupted,
for example in drought conditions, a shortage of
calcium can occur within the plant and deficiency
symptoms appear in the weeks following. The
symptoms are called a number of different names
depending on the crop: brassicas and lettuce
(tipburn), celery (blackheart), tomato (blossom end
rot), potato (internal rust spot). The most effective
way to counter calcium deficiency is make sure that
your crops are well supplied with water by
irrigating in dry spells.
Black heart in celery.
Trace elements
Vegetables rarely suffer from trace element deficiency. The most common one is
boron deficiency in swedes and turnips which causes a disorder called
brownheart. This is a brown discolouration in the centre of the bulb and to
prevent it boron should be applied preventatively before the symptoms develop.
Alkaline soils and dry summers are factors that can increase the incidence of
brownheart. Boron deficiency can also show up in celery where its known as
cats claw. High pH soils can exacerbate low boron levels in the soil due to lockup of the available boron. On the other hand very low pH soils can induce
molybdenum deficiency in cauliflowers causing the formation of narrow, strap
shaped leaves known as whiptail. Sometimes you may come across iron deficiency
symptoms in module raised plants if they are watered with hard water. This
causes the pH of the compost to rise and you end up with an induced iron
deficiency. To cure the problem apply some iron sequestrene. Applications of
compost or manure will ensure a plentiful supply of trace elements.
Organic matter
Additions of organic matter usually garden compost or farmyard manure are
beneficial for several reasons. It benefits soil structure, improves water holding
capacity and adds in small amounts of major and minor elements. It is
13
particularly beneficial for improving

heavy and light soils. Compost, which is
formed from the decay of plant material,
is valuable for the humus and recycled
nutrients it contains. All garden refuse,
cut grass, kitchen waste, etc. should be
collected into a heap and when rotted,
dug into the soil. It is important to
exclude from the heap the remains of any crop suffering from disease such as
onions which have been attacked by white rot, or any brassicas which have
suffered from club root. Farmyard manure is also a great source of organic
matter when available. Spent mushroom compost, available in certain outlets,
is pleasant to handle and compares more than favourably with farmyard
manure and compost in nutrients.
Organic matter should be dug in during the autumn or winter months at a rate
of about 5-10 kg per m2. It can also be applied prior to planting, as for example
with potatoes. Organic matter is normally applied in rotation to the high
nitrogen demanding crops: transplanted brassicas, celery, leeks, courgettes,
potatoes and spinach . Final word of warning dont be tempted to apply
copious amounts of organic matter every year to the same ground it is
possible to overdo a good thing.
Fertilisers
Fertilisers are as valuable in the garden as on the farm if used intelligently to
supplement moderate dressings of farmyard manure or compost. They supply
to the crop the particular nutrient that it most requires. Fertilisers come in two
forms straights and compounds. Straight fertilisers contain just one element,
such as nitrogen or potash. Compound fertilisers contain more than one
element and usually consist of various mixtures of nitrogen, phosphorus and
potash or N-P-K. The advantage of using compounds is that its a handy way of
applying all three major elements to a crop.
The standard notation on a box or bag of fertiliser is to give a percentage figure
for nitrogen, phosphorus and potash or N : P : K in that order. For example
a bag of 7-6-17 contains 7% nitrogen, 6% phosphorus and 17% potash. Take
note that UK sourced fertiliser always quote P as P2O5 and K as K2O. In Ireland
14
we use elemental P and K. To convert P2O5 and K2O to P and K multiply by 0.44
and 0.83 respectively. Nitrogen in both countries is quoted in elemental N.
One normally applies fertiliser just before sowing or planting a crop sprinkle
the fertiliser across the ground and lightly rake or fork in. One should apply
only as much fertiliser as is required to grow the crop in accordance to the
results of a soil sample and the following rates are only a guideline where that
information in not available.
Straights
Superphosphate 8% P
Apply 35-50g per m2 of 8% P at time of sowing or transplanting.
Sulphate of Potash 42% K
Apply 30g per m2 at sowing or transplanting.
Sulphate of Ammonia 21% N, 24% S
This is the commonest form of nitrogen available to the gardener and is also a
useful source of sulphur. Works within about a week of application under
warm, showery conditions. With constant use will tend to acidify the soil. Apply
at 15-30 g/m2.
Calcium Ammonium Nitrate (CAN) 27% N
This is the most commonly used straight nitrogen in agriculture. Slightly faster
acting than sulphate of ammonia. Apply at 15-30 g/m2.
Compound Fertilisers
There are various compound artificial manures on sale which incorporate the
three main fertilisers i.e. nitrogen, phosphate and potash and sometimes other
elements such as sulphur or boron. Granular compound fertilisers such as
10:10:20, 8:5:18+ B or 7:6:17 are ideal for the vegetable garden and do not have
to be mixed. They are normally available at agricultural outlets. Apply at a rate
of 50-90g per m2, or preferably in accordance with the results of a soil test.
There are other proprietary compounds on the amateur market suitable
for vegetables and these should be used according to the manufacturers
instructions. Organic based fertilisers are also available in retail outlets.
15
Liquid Fertiliser
Many proprietary brands of liquid
fertilisers are available which when
diluted with water according to
instructions
are
valuable
for
vegetables as a quick acting source
of nutrients. However it is a much
more expensive way of applying
nutrients than using solid fertilisers.
This image shows nitrogen deficiency in
parsley. It shows up in the older leaves as
a pale green to yellow colour with the
younger foliage showing a healthier
darker green.
Rotation
The very first farmers back about 10,000 years ago would have discovered two
things about rotation pretty quickly. Firstly, that breaking fresh ground gave
them healthy crops; secondly, that if they kept cropping the same bit of ground
with the same crops they became unhealthy due to a build up of pests and
diseases. And so they would have begun to move or rotate their crops
around in order to maintain good yields.
The basic idea is that pests and diseases are usually specific to each family group
of vegetables and that if you move the groups around youll minimise the
likelihood of an outbreak. But in a sense rotation is a bit of a nonsense for the
small plot vegetable grower, as true rotation is something that only a farmer can
carry out by moving his crops from field to field. Take carrot fly for instance. Its
capable of flying up to a kilometre from its overwintering site and this years
carrot crop thats 2km away from last years infected crop is unlikely to be
attacked from that source. But the carrots in your allotment that are only a few
metres away from the previous years infected crop will get attacked.
The other problem with small plots is that in the process of growing your
vegetables youll inadvertently move soil from plot to plot via boots, tools and
16
wheelbarrow and in this way soil borne diseases like white rot and clubroot
can be spread around.
Hence its not easy to rotate crops in a small area but the advice would be to
practice it in as far as possible. Divide your crops into roughly six groups: brassicas
(cabbage, swede, Brussels sprouts, cauliflower, broccoli, kale), legumes (pea,
bean), alliums (onion, scallion, leek, garlic), carrot group (carrot, parsnip, parsley,
celery), solanums (potato, tomato) and the last group is everything else. The idea
is not to grow any one group in the same ground more than 1 year in 4 or 5.
Notwithstanding the last piece of advice, an even simpler system is to divide
your plot into three evenly sized areas and split up your vegetables into three
groups: leafy crops (includes all the brassicas), peas and beans and root crops.
Then follow the sequence in the table below.
Year 1
Year 2
Year 3
Plot A
Roots
Peas and beans
Leafy crops
Plot B
Peas and beans
Leafy crops
Roots
Plot C
Leafy crops
Roots
Peas and beans
The above rotation would be particularly useful if you are growing organically
without access to artificial fertilisers. Leafy crops are high nitrogen crops, roots
are low nitrogen crops and peas and beans fix nitrogen and make it available
to the following crop. Hence leafy crops follow after the legumes and root
crops are placed at the low point in the nitrogen cycle.
The main problems that can stem from poor rotations include club root and
white blister in brassicas, white rot and downy mildew in alliums and eelworm
in potatoes all of which are difficult to eradicate once they become established.
Other reasons for rotating crops include evening out what nutrients are
absorbed from the soil as crops differ in their requirements and improving soil
structure. Varying the crops grown allow for different types of cultivation to
take place and this can help to preserve good soil structure. For example the
deep cultivations required for a potato crop are different to the more shallow
cultivations required for an onion crop.
17
Weed Control
Weeds are an ever present problem for the vegetable grower. Studies of soil
taken from fields cropped commercially with vegetables have shown that it is
quite common to find 10,000 seeds per square metre in the top 15 cm of soil,
with the figure rising to 75,000 in very weedy fields.
Weeds of tilled ground are usually annuals that have the ability to grow, flower
and set seed quickly e.g. chickweed, groundsel and shepherds purse. They have
adapted to survive in cultivated ground and will germinate throughout the year
any time the soil is disturbed. They compete with the crop for space, light and
nutrients but the effect on the crop can vary. For example, weeds can wipe out a
direct drilled onion crop if not dealt with but have far less of an effect on a
transplanted crop of cabbage.
The best way to beat weeds is to keep on top of
them by constant use of a hoe. The weeds
should be eliminated when they are quite small
and never allow them go to seed. There is no
need for 100% elimination weeds growing
within the crop-row are not a problem.
Perennial weeds should be forked out before
they become a problem.
Groundsel: abundant tillage
An alternative to hoeing is the use of black weed which has the ability to
grow, flower and set seed all
polythene mulch. Black polythene laid on the year round.
ground prevents weed growth, conserves
moisture and raises the soil temperature. It is of particular benefit with certain
half-hardy vegetables such as courgette, melon, sweetcorn etc. Ideally the
surface should be level and pierce the plastic with a sharp knife wherever water
ponds to allow rainfall to drain through.
Another idea you might consider to reduce the amount of hoeing is the
creation of a stale seedbed. This is where you prepare the area for sowing or
planting several weeks before, to allow weed seeds to germinate. Then spray
them off using a glyphosate product such as Roundup. As the weeds are only
in the seedling stage you can get away with using reduced rates suggest half
rate. Its quite safe to sow or plant the day following treatment.
For weed identification please refer to www.teagasc.ie and search for
Illustrated Guide to Tillage Weeds.
18
Pests and Diseases

Lets get the bad news out of the way at the beginning. Pests and diseases go
hand in hand with growing vegetables and are a natural part of the ecosystem.
So wed better learn to live with them.
Its a sad but inevitable fact of life that the fruits of your labours can be
attacked by a wide range of pests. However the good news is that with a little
bit of care and attention we can sidestep most of them provided we know
what to expect and take the necessary precautions.
Good control starts with good husbandry. Just like ourselves, if a plant is well
looked after, its far less prone to attack. Thorough preparation of the soil and
use of manure or compost will pay handsome dividends in reducing the
incidence of pests and diseases.
That said there will always be some pests that inevitably show up in certain
crops. Cabbage root fly, carrot fly, caterpillars, slugs and aphids are sure to leave
their calling cards at some stage during the season.
So what can we do? You have the option of using
pesticides, organic methods or a mixture of both. In
a garden situation the organic option is best with a
couple of exceptions slugs are one and the use of
pellets is probably the handiest way of controlling
this particular pest.
And indeed you may be faced with Hobsons choice Large white butterfly
in relation to turning organic the chemical you caterpillar.
once used is no longer there in a lot of cases. There
are now very few insecticides or fungicides available to the amateur market.
PESTS
An excellent idea to keep the majority of pests off your crops is to cover them
with an insect proof cover. You have two choices: fleece or insect netting. Both
of these can be placed directly over your crops and anchored at the edges
they will keep the majority of pests out but still allow light and water to pass
through. They are put on before the pest arrives and its taken off when the
19
crop is past the susceptible stage of attack. Fleece

is a light woven material and insect netting is a
heavy duty plastic both of which can be purchased
in good garden outlets. Nets are considerably more
expensive than fleece but last far longer hence
probably cheaper in the long run.
Cabbage root fly
Cabbage root fly is a major pest of all the brassicas. The damage it does is
unmistakable plants dying off with white maggots on the roots. You are
courting disaster unless you take some precautions. The next time you are
replacing the dining room carpet, dont dump the old one. Cut it into 10 cm
squares, with a single cut to the middle and slide it into place around the base
of each brassica transplant. This will stop the maggots from getting to the
roots. Alternatively cover your brassicas with fleece or net.
Cabbage root fly start laying eggs about 20 April but in cold springs it can be
as late as 8 May. Experience has shown that initial egg laying coincides with
the start of flowering of hedge parsley when about
1 in 20 of its flower heads are showing white. The
first generation peaks in May (usually around mid
May), so by covering your brassica plants from mid
April to mid June, youll avoid the worst ravages of
this pest. Young plants are the most susceptible and
if you can get them past this vulnerable stage you can take the covers off, unless
you want to protect against other pests such as caterpillar. Numbers are
generally low in June but unfortunately there is a second generation to
contend with in July and August but its far less damaging than the first.
Cabbage root fly is a ubiquitous pest that shows up every year and to ensure
complete control cover your crops from mid April to mid September.
Carrot fly
Carrot fly is a major pest of carrot, parsnip, celery and parsley all members of
the same plant family, the Apiaceae. The small larvae of the adult carrot fly mine
the roots and can totally destroy a crop. You may be lucky the first time you grow
these crops and avoid damage but local populations of the pest can quickly build
up. There are normally two generations per year May to mid June and late July
20
to September. Celery is worst affected by the

first generation while damage in carrots and
parsnips normally shows up from September
on. Parsley is less prone to being attacked but
will suffer with high populations of carrot fly.
The adult fly uses smell, vision and taste to
locate its host and most of them will
originate from a previously damaged crop
within a square kilometre of your crop.
Carrot fly barrier with over-hang.
To prevent or reduce an attack from carrot fly try one of the following:
Cover your crop with fleece or net from late April and leave it on until
around mid September.
Surround the area with a 60 cm high wall with something like clear plastic.
The carrot fly isnt a strong flier and wont be able to find the carrots if they
are barricaded off. The picture shows a metre high net barrier with a lip at
the top for extra security it managed to protect a plot 10 m wide.
Sowing them in a garden frame or polythene tunnel will also probably be
effective in warding off the ravages of this pest.
Sow in mid May to avoid the first generation and put covers on from mid
July to mid September.
Theres a new insecticide on the amateur market which contains lambdacyhalothrin, the same active that commercial growers use for carrot fly
control. It works by killing the adult fly and must be used preventatively.
Use it only when the fly is active. The second generation spray protection
programme usually starts around 20 July and would be applied every two
weeks up to mid September.
Bean seed fly
Bean seed fly is a localised and occasional pest of beans, spinach, onions,
cucurbits, beet, sweetcorn and brassicas. The flies emerge in March and April
and the female lays eggs on freshly disturbed ground. They are attracted by
decomposing organic matter and plant debris. The eggs hatch after a few days
into white larvae, similar to cabbage root fly maggots, and grow to 5-8 mm in
length. Its the larvae that do the damage by feeding on buried bean seed, on
emerging Alliums and recently planted cucurbits. There are several generations
21
and attacks can occur until early autumn. Commercial growers use seed
treatments to combat the pest on susceptible crops. A cultural control method
is to delay sowing for about 10 days after cultivating to reduce the risk of attack.
Slugs
Common to every field and garden these pests can wreak havoc if present in
large numbers. Given the amount of shelter available in an average garden they
are a bigger problem in small plot areas than in the open field. There are several
species including the grey field slug, the black slug and the keeled slug.
All are active throughout the year provided temperatures dont go too low and
activity is highest in warm, humid weather. Its impossible to eliminate slugs so an
integrated approach, using several different techniques is more successful than
relying solely on pellets. The first step is to minimise areas where slugs can shelter
keeping the area around the vegetable plot tidy and controlling weed growth
within it can help. Ensure that the remains of previous crops are dug in, or raked
off and removed to the compost heap. Repeated cultivations, especially if carried
out using a rotavator can also help in reducing numbers.
Use of slug pellets is the commonest method of control. They are based on one
of three chemicals: methiocarb, methaldehyde and ferric phosphate; only the
latter two are available for garden use. There is little difference in efficacy
between any of the actives. Pellets are usually cereal based to make them
attractive to slugs and coloured blue to make them unattractive to birds and
other animals. The methaldehyde based pellets immobilises the slug and
subsequently dies from desiccation. They can recover if the weather turns wet.
Ferric phosphate pellets slowly poisons slugs and once ingested stop feeding.
They become less mobile and die within 3-6 days normally underground as
dead slugs are not usually visible overground. These pellets are more expensive
than metaldehyde but more eco-friendly they break down to iron and
phosphate and are harmless to other wildlife. Use pellets sparingly and bear in
mind that they will remain effective for 1-2 weeks depending on weather; they
tend not to last in prolonged wet spells. Apply directly after sowing or planting
out a susceptible crop.
Other controls:
Nematodes: expensive but effective method of control. Must be sprayed on
in rainy weather and will last for about 6 weeks.
22
Traps: use of hollowed out grapefruit or orange, planks or black plastic bags
laid on the surface of the soil will attract slugs which can then be
subsequently destroyed. Beer traps are also effective in attracting and
drowning slugs.
Predators: encourage frogs, hedgehogs and ground beetles into the garden
to help keep slug populations under control.
Barriers: there are a variety of barrier materials sold to keep slugs away from
desirable plants of varying usefulness it must be said.
Go out in the late evening or early morning and dispose of any slug or snail
you come across.
Slugs will eat a variety of vegetables but not all. They prefer soft rather than
fibrous material. However if choice of food is limiting they will graze on less
palatable crops. The worst losses can occur at the seedling stage when complete
crop rows can disappear. They mostly feed at night but if weather conditions
are humid enough they continue during daylight hours as well. Having found
a desirable food, slugs remember its location and return to it from their resting
areas for subsequent feeds. The following table lists the susceptibility of various
crops to slugs under three categories. To explain what intermediate means,
take carrot for example. Slugs will eat seedling carrots, wont touch the more
mature foliage but will eat the root when it forms. Commercial carrot growers
dont need to apply pellets but in a garden situation it may be necessary.
Susceptible
Intermediate
Resistant
Brassicas
Spinach
Leek
Lettuce
Peas
Courgette
Celery
Broad bean
Beetroot
Rhubarb
Onion
Herbs (ex. basil)
Potato
Scallion
Sweetcorn
Carrot
French bean
Parsnip
Runner bean
Asparagus
23
DISEASES
A wide range of diseases attack vegetables and we have a climate that is tailor
made for the spread of disease. So we need to understand the nature of
disease, be able to recognise the common ones and find out how best to deal
with them.
Plant diseases are caused by fungi, bacteria or viruses. But its important to
realise that fungi and bacteria are also enormously beneficial human life
would be impossible without them. They carry out a myriad of essential life
processes including nitrogen fixation and sorting out your compost heap.
There are many different species of fungi including mushrooms, mildews,
moulds and yeasts. They are made up of thin thread like structures called hyphae
and a visible mass of hyphae is called a mycelium. They propagate themselves by
producing spores that are spread by wind and rain splash. There are two types
of fungi: parasites and saprophytes; but one thing they have in common is the
inability to manufacture their own food unlike plants. Saprophytic fungi live
off dead material and are commonly found in the soil and on rotting plant and
animal material. Parasitic fungi are the ones that attack plants but in general
dont kill them. The hyphae penetrate between the cells, secreting enzymes to
break down the tissues and absorb the digested molecules.
Bacteria are tiny single celled organisms which increase in number by dividing
in two. The majority of plant disease is caused by fungal pathogens but bacteria
can occasionally cause problems such as blights, leaf spots and soft rots. Unlike
fungi bacteria do not produce spores and hence dont get spread around by the
wind. Plant pathogenic bacteria can exist on leaf surfaces without causing any
problems; but if for any reason they multiply to sufficient numbers they are
able to enter the plant through wounds or natural openings such as stomata
or hydathodes. Once inside the plant they multiply and cause disease. Bacteria
spread from plant to plant by rain or irrigation splash and are also readily
transported around by contact e.g. machines, tools, trays, clothing or hands. A
number of bacterial diseases are seedborne, e.g. Xanthomonas in Brassicas if
the seed is sown the disease can show up later in the growing crop. Plant
pathogenic bacteria do not survive in the soil unless on partly decomposed
plant material the exception is Streptomyces scabies which causes common
scab in potatoes and other root crops. Bacterial diseases in vegetable crops have
24
become more common in recent years due to wetter summers its a pathogen
that develops in spells of wet weather. Examples of bacterial diseases are
bacterial leaf spot on Brassicas, halo blight on beans and blackleg on potatoes.
Viruses are tiny, non-cellular structures that can only be seen with an electron
microscope. They can attack a wide range of vegetables but not frequently.
Most need a vector to transmit from plant to plant aphids would be the
commonest example of a vector. Examples of viruses are beet yellows virus,
celery mosaic virus and virus x in potatoes.
Ring spot (Mycosphaerella brassicicola)
This is one the commonest diseases in brassicas, important on winter
cauliflower, cabbage, kale and sprouts with swedes much less susceptible except
in the wetter parts of the country. Its worst in wet seasons and is associated
with intensive brassicas production areas. It starts off as small dark spots 3-5
mm in diameter which eventually enlarge to 2-3 cm. Leaf spots are restricted by
veins so can appear angular in shape this is a distinguishing feature in
comparison to Alternaria leaf spot. Later on tiny black fruiting bodies appear
in concentric rings. Badly affected leaves turn yellow and wither prematurely.
The chief sources of infection are spores that blow in from a nearby crop or
from plant debris on the soil.
White blister (Albugo candida)
The characteristic chalky white pustules on the leaves of brassicas make this
disease an easy one to identify. The disease attacks most brassicas bar swedes.
Its a common disease in the more intensive brassicas growing areas of the
country and an awkward disease if it appears in the vegetable garden.
Awkward because it will tend to persist in the soil from resting bodies known
as oospores and also as there are no chemical controls available on the amateur
market. It doesnt tend to reduce yield but does disfigure the plant. Its worst
effects are on sprouts where a bad attack on the buttons will render a crop
unmarketable. The initial infection can arise from the oospores and subsequent
infection within the crop from airborne spores that arise from the pustules.
White blister can also attack shepherds purse but that strain of the disease will
not attack vegetable brassicas.
25
Onion neck rot (Botrytis allii)

If you find your onions going soft in store then the most likely cause is neck rot.
This common storage disease can originate in the sets or seed you buy. Both are
possible carriers of Botrytis spores that may systemically infect the developing
crop. Few if any symptoms appear during the growing season; but with infected
sets one can get yellow leaves showing up in the crop. At the end of the season
when the foliage begins to senesce the fungus sporulates and can infect the
neck of the onion where the crop is topped or through breaks in the foliage
when the tops bend over. The mycelium of the fungus then grows down into the
bulb. After several weeks in storage a water soaked or light brown decay will
appear on the neck of the onion along with grey sporulation. At a later stage
small black resting bodies or sclerotia will develop on the surface of the bulb.
The disease further develops to spread throughout the bulb which eventually
rots. To reduce the chances of getting this disease buy your sets or seeds from a
reputable outlet heat treated sets should be free of the disease. The other
thing to do is to ensure that the necks of the onion are completely dry before
storing the bulbs. Take note that any sclerotia that reach the soil can also act as
an infection source and can survive for two years on the buried debris.
Onion leaf blight (Botrytis squamosa)
This leaf spotting disease is most commonly associated with salad onions but
can also attack the foliage of bulb onions. The source of the infection is
airborne spores that originate from neighbouring crops, debris from previously
infected crops or from sclerotia in the soil. The initial symptoms are the
formation of small white elliptical spots surrounded by a green halo. With time
these spots coalesce and lead to total bleaching of the foliage and general
collapse of the plant. Dont confuse the initial symptoms of the disease with hail
damage on the leaf which can look very similar. Twirl the leaf between your
fingers and if the damage is one sided its weather damage, and if the spotting
is all around its Botrytis. Leaf spot often breaks out after a spell of warm muggy
weather and the disease can rapidly spread across an entire field.
Potato blight
This airborne disease arrives every year, initially attacking the leaves and stems
but worse damage occurs if the spores wash down to infect the tubers. You have
a number of options to reduce your risk:
If you plant earlies or second earlies you have a good chance of harvesting
before the blight season gets into full swing.
26
Choose a variety with good blight resistance characteristics. To help you pick
the right ones see the table below. Sarpo Mira, though not totally resistant
to blight, is head and shoulders above the rest of them and with this variety
you can get away with little or no blight spraying. If you choose varieties like
Orla or Setanta with good tuber blight resistance you can get away with
reduced number of sprays (2-3 perhaps).
Listen out for blight warnings on the radio and tv and spray with mancozeb
(if available) at regular intervals from June-July onward.
Learn to recognise blight symptoms on both the leaf and stem and remove
diseased tissue as soon as its spotted this will reduce the chances of the
disease spreading further within your crop.
If blight gets a hold in your crop and the tubers are of sufficient size, cut
down and remove the tops to prevent the spores being washed down by the
rain to infect the tubers. Do not dig the crop for a minimum of two weeks
to allow spores on the soil surface to die off.
Weather
Weather is one of the major drivers of plant growth. The interplay of frost,
rain, wind and sun all conspire to thwart or aid our ambitions to grow good
crops. That ideal summer combination of sunshine and showers is one to hope
for but seldom happens. The reality is that we get periods of wet or dry, cold
or warmth which in turn gives periods of poor, middling or good growth. But
in general over the course of a year the weather tends to even itself out. A
worrying trend in the recent past has been an increase in extremes of weather.
This may be related to climate change but whatever the cause it does not make
the task of growing vegetables any easier.
When it comes to planned sowing and planting dates the calendar may well
have to be ditched if the weather turns too wet or too cold. Experienced
growers will tell you that a crop that is mucked in in unfavourable conditions
will often be passed out by a crop planted later on in good conditions. So be
patient, and delay that sowing or planting until soil conditions or soil
temperature come right, even if it means waiting a week or three.
27
Hardiness
The vegetables we grow in Ireland originate from many different parts of the
world and as such vary in hardiness. There are two categories of hardiness:
hardy and half-hardy. Hardy vegetables are those that survive the normal Irish
winter and can be harvested during the coldest months. Half-hardy vegetables
are those that are damaged by frost and are grown and harvested during the
warmer months. So when it comes to sowing or planting these types we need
to be mindful of late spring frosts and complete the harvest before winter
closes in. Some vegetables such as beetroot lie in-between the two categories
as they will survive outdoors in a mild winter lets call them almost hardy.
During 2010 we experienced a return to frosty conditions that
hadnt been experienced for many years. Air temperatures
greater than 15C were recorded at several meteorological
stations. The temperature you see on tv weather maps is air
temperature which is measured at a height of 1.25 m. But a
more meaningful figure for vegetable
crops is the grass minimum (Gmin)
which is measured at ground level
also known as ground frost. The grass min can be
anything up to 5-6C lower than air temperature. If
you wish to check grass min temperatures you can
find them on the Met Eireann website under Latest
Weather > Yesterdays Weather, Gmin. The
photographs show frost damage to sprout buttons
and damage to the core of storage cabbage.
At temperatures below 0C frost occurs and ice forms within the plant. The
damage that subsequently occurs will vary from none to total tissue destruction
depending on the hardiness of the plant and the degree of frost. Other factors
can also affect the outcome: older tissue is more prone to frost damage than
younger tissue and a rapid rate of thaw can exacerbate the situation.
One sometimes sees the instruction on a seed packet or bag of seed potatoes
to sow or plant out after the last frost. So how do you know when the date of
the last frost will be? The short answer is, you dont. However past weather
records and personal experience can help us in picking a date that hopefully
will be correct. The table below shows the average and extreme dates of last
spring and first autumn air frosts, 1971-2000.
28
Station
Mean
Valentia Obv
Claremorris
Kilkenny
Clones
26 March
28 Apr
29 Apr
26 Apr
Last
Extreme
29 Apr
20 May
30 May
31 May
Mean
25 Nov
25 Oct
13 Oct
30 Oct
First
Extreme
16 Oct
8 Sep
10 Sep
8 Sep
The last date of the last ground frost can be considerable later that the date of
the last air frost and has the potential to damage half-hardy crops in the
ground at that stage. The table below gives the average and extreme dates of
last spring and first autumn ground frosts at the specified stations.
Station
Mean
Valentia Obv
Claremorris
Kilkenny
Clones
4 May
28 May
17 June
9 May
Last
Extreme
15 June
28 Jun
30 Jun
29 Jun
Mean
18 Oct
11 Sep
7 Aug
24 Aug
First
Extreme
31 Aug
3 July
1 Jul
3 Jul
The following table is an attempt to rank vegetables in order of hardiness. Take

note that relative hardiness can depend on the growth stage. In the case of
rhubarb the dormant stools seem to be totally frost resistant but the young
shoots produced in spring can be prone to damage. Swedes are pretty hardy in
the mature stage but can bolt due to cold weather if sown too early. The
experience of 2010 has shown that with the exception of parsnips virtually all
vegetables will develop frost damage if temperatures go low enough. You are
heading into the danger zone with Gmin temperatures of -10C or greater.
29
Hardy
Almost hardy
Half-hardy
Parsnip
Rhubarb
Kale
Garlic
Cabbage
Leek
Swede
Brussels sprouts
Broad bean
Winter cauliflower
Perpetual spinach
Carrot
Storage cabbage
Beetroot
Scallion
Parsley
Onion (overwintered)
French bean
Runner bean
Courgette
Marrow
Pumpkin
Celery
Potato
Sweetcorn
Broccoli
Lettuce
Bolting
A lot of vegetables are biennials; that is they grow
vegetatively in the first year and flower and set seed in the
second. Examples include most brassicas, celery, beetroot,
onions, leeks, carrots and parsnips. Sometimes if they are
planted or sown too early they can get a cold check and
start to flower in year one this is known as bolting.
Biennials require a period of cold to initiate flower buds
this takes place naturally during the winter and is a process
known as vernalisation. However they are insensitive to
cold in the seedling or young plant stage this is the
juvenile stage. The optimum temperature for vernalisation
is usually within a degree or two of 4C at lower temperatures growth
processes stop and at higher temperatures above about 12C there is no
stimulus to flower.
Its interesting to note that if a warm day follows a cold night it tends to cancel
out the vernalising effect of the lower temperature but if cool days follow a
succession of cold nights then a crop is set along the path to flowering. As a
rough guide it only takes about 6 weeks of cold weather to initiate flowering
but the effect takes a while to show. A crop that bolts in early summer will
have encountered a cold spell sometime during the previous spring.
30
So for a crop to bolt it has to have to be of a certain age and endure a period of
cold. The cold conditions are a combination of temperature and time and can
arise from a fairly low temperature for a long time or a low temperature for a
shorter time but it takes more than a few frosty nights to trigger the reaction.
The table below shows the differences with the swede variety Magres in sowing
dates and whether the crop is covered or not. The covering material was
perforated polythene which would have been removed in May. The trial was sown
into modules under glass in January and planted out at the end of March and also
direct drilled outdoors in March. You can see the effects of cold spring weather on
both of the uncovered crops, and the elimination of bolting by covering.
Kinsealy Research Centre Trials, 1996
Treatment
Jan sown, 308 cell + cover
Jan sown, 308 cell
Mar sown outdoors + cover
Mar sown outdoors
t/ha
40.0
22.3
16.6
6.3
Bolting %
Harvest date
0
83
0
98
28/6
3/7
3/7
17/7
Variety can play a part and plant breeders do their best to develop bolt resistant
cultivars. Beetroot is a crop that can run to seed if sown before April but if you
choose a variety such as Bolthardy thats been selected for its cold tolerance, it
can be sown in March. Breeders are also working hard to select out resistant
strains of coriander which is also prone to bolting.
Daylength can also influence time of flowering. Annual vegetables such as
radish, spinach and lettuce are triggered into flowering by the length of the
day. Under normal circumstances a lettuce will only bolt after hearting. It is
responding to the long days of summer in doing this, and at the height of the
summer there may be only a few days between the heart being formed and the
formation of a flowering shoot. But if the crop suffers a stress for example if
the weather turns hot and dry and the crop is left unirrigated then the lettuce
may well go straight to the flowering stage without forming a head. The same
holds true for radish and spinach.
31
Varieties
With hundreds of varieties available to the vegetable gardener it can be
puzzling to decide which ones to choose. While some of the varieties that are
available in the garden catalogues have been around for many years, plant
breeders are continuously trying to produce new and improved varieties of all
crops. Varieties can be divided into two types hybrids (designated F1) and
open pollinated or standard varieties. Hybrids are becoming increasingly
common in amateur catalogues due to their widespread use in commercial
growing. They offer a number of advantages over open pollinated varieties,
chiefly increased vigour and uniformity, though the latter is not always
advantageous to the gardener. The downside of hybrid seed is that it costs
more than standard seed. The best advice is to try out different varieties and see
which ones suit your conditions best. The varieties mentioned in the book are
all well tried and tested.
Plant Spacing
Different vegetables require different amounts of room to grow. And hence
we space them accordingly. But it can get confusing when no one seems to
agree what the optimum spacing should be! One can look up five different
books and get five different spacing for the same vegetable.
But why do we space our vegetables the way we do and what are the end
results for the spacings we choose? There are two parameters by which we can
define spacing: population and pattern. For example if we were to plant a
single cabbage plant in a hectare of fertile ground the population would be
one per ha. We would grow a fine big cabbage but the overall yield would be
pretty dismal. Say we were to plant two per hectare but put both plants into
the one hole wed end up with two poor plants. So the pattern is how we
space out our population. If we choose a different pattern and space them well
apart, wed end up with two very large heads.
And so as we keep increasing the population and keep them evenly spaced,
the overall yield per hectare goes up in a step by step incremental fashion. As
we pack yet more plants into our plot we notice at a certain stage that while
32
the overall yield continues to increase, the individual size of the heads begins
to decrease due to the competitive effects of ever closer spacing. We eventually
reach a point where the yield is at a maximum with a certain plant population.
This holds true for all crops.
But what happens if we continue to put more plants into our plot? It all
depends on the crop. With a crop like beetroot the yield will plummet quite
rapidly as a beetroot requires a certain minimum framework of leaves to form
a harvestable head. At very high populations all you will produce is leaves.
However with a crop like carrots as the plant population is increased the overall
yield is maintained but the size of the individual roots reduce. This can be useful
as it allows us to control the size of carrot whilst maintaining maximum yield.
So as you can see spacing has a very direct effect on total yield and on the
individual size of the vegetable. There is another effect timing of harvest. If
we are looking for earliness in a crop or indeed sowing late in the season, the
spacing we choose will have an effect on those outcomes. The wider you space
the earlier the crop and the better chance we have of harvesting a late crop.
As you will have gathered by now spacing is a very useful tool for the vegetable
grower.
Getting back to pattern, you would think the best system would be to space
your plants as evenly as possible; but the standard advice is to grow most crops
in rows, where everything can look unnecessarily crowded. To find the reason
for this we have to go back to the agricultural revolution to the invention of
the seed drill and mechanical hoe. For these inventions to work, crops
necessarily had to be grown in rows. And so we use rows in the vegetable
garden for weed control.
Growing in rows does not necessarily have a detrimental effect on yield.
Broccoli is remarkably unaffected by row spacing up to a distance of 60 cm. So
spacings of 60x10 cm, 40x15 cm and 30x20 cm will all yield approximately the
same in this example the population per m2 is the same but the pattern varies.
With parsnips if the ratio of the between-row spacing to the within-row
spacing does not exceed 2.5:1, yield is not reduced. For a population of 22 per
m2 the maximum row spacing would be 34x13.6 cm but perhaps using a ratio
33
of 2:1 is simpler which would work out at 30x15 cm both spacings will give
you approximately the same population. Lettuce is an example of a perfectly
round crop that works best at even spacings length by breath.
And as mentioned dont get too hung up about the spacings mentioned in this
book or in any other for that matter. They are only suggestions and spacings
will vary according to your growing system beds, drills or on the flat and
even to the width of your hoe. They will also vary in accordance to what size
you want your particular vegetable to be. For example higher populations per
m2 will reduce the individual head size of broccoli. Or you might choose slightly
wider spacings for an early or late crop. If you see a reference to 30x15 cm in
the book, this means a 30 cm row spacing and 15 cm in-row spacing.
Watering Vegetables
Despite the general impression that it rains a lot in this country, in most years
there are dry spells during the growing season which affect plant growth. In
response growers will irrigate their crops to maintain continuity and to improve
quality and yields. Only very rarely will unirrigated crops actually die.
Soils play a vital part in water availability. Gardeners will be aware that a light
sandy soil holds less water than a heavy clay soil, but less will appreciate the role
of soil structure. A deeply dug, well-structured soil will allow for a bigger root
system that is better able to tap the available water supply. And the best way
to improve soil structure is by digging in compost or manure.
So how much water do you need to apply, when is it best applied and what
crops will benefit most?
34
In the height of the summer a crop at

full canopy can lose up to 2-3 litres of
water per square metre per day. As a
general rule its best not to water a
little and often as you will lose a high
percentage of it through evaporation.
And with the exception of seedlings
and transplants its not worth while
giving any less than 10 litres per square metre at any one time and greater than
25 is excessive.
Crops vary in their requirements for water. For example in commercial practice
celery is always irrigated while swedes are virtually never irrigated. Apart from
celery other crops that are frequently irrigated are lettuce, potatoes (especially
earlies), scallions, early cauliflowers, courgettes and spinach.
In an ideal world we would irrigate every time our crops need water but time
constraints and hose pipe bans may well conspire to limit how much water we
can apply. Fortunately research has shown us the critical times of a crops life
cycle when response to irrigation is greatest. All crops will be responsive at crop
establishment either at sowing or transplanting. If sowing in dry weather run
a little water along the open drill before sowing. Other stages that have been
identified are:
Cabbage, cauliflower, broccoli: 2-3 weeks before expected harvest.
Potato: when the tubers are marble sized.
Peas and beans: at flowering and during pod swelling.
Celery, lettuce, courgette: these crops (especially celery) require frequent
watering suggest weekly.
Carrot, parsnip, beetroot: apply 16-22 litres per m2 every 2 weeks.
Onion: during the early plant growth stage.
1 inch of rainfall = irrigation equivalent of 250,000 L/ha = 25 L/m2

1 mm of rainfall = 1 L/m2
35
Plant Raising and Direct Drilling

The vast majority of vegetables are
propagated from seed. As mentioned
previously we either sow the seed direct
into the ground where the crop is to
mature or else its raised in a seed bed or
seed tray and transplanted out at a later
stage into the vegetable garden.
The primary reason for transplanting is the more economical use of space and
time. For the more widely spaced vegetables it makes more sense to propagate
expensive seed under cover and plant out at exactly the plant population you
require; it also allows for a quicker turn around of the ground and makes weed
control that bit easier. The development of half hardy crops like courgettes and
French beans can be speeded up if they are initially raised under protection and
will give you greater yields by seasons end in comparison to drilling.
The main disadvantage to transplanting is the check to
growth that occurs mainly from damaged roots, and the
gardener is conscious of doing everything in his or her
power to ensure that transplants establish quickly and
grow on with minimal check. The development of
modular propagation has greatly reduced root damage
and improved speed of establishment.
Crops like carrots and parsnips that have a tap root and
are grown at high densities are of necessity direct drilled.
Swedes are generally direct drilled but the early crop is sometimes transplanted
but growers will tell you that the root shape is always poorer with the
transplanted crop as against the drilled crop. Sweetcorn can be started indoors
but its a poor transplanter and will establish better from direct drilling.
Seed to germinate requires oxygen, moisture and a certain minimum
temperature. One can divide vegetables into 3 groups in relation to minimum
soil temperature requirements for germination:
36
5C: brassicas, lettuce, pea, broad bean

7C: carrot, parsnip, beetroot, onion, scallion, leek
10-12C: French bean, runner bean, courgette, sweetcorn, tomato
These are minimum temperatures they will germinate more quickly at higher
temperatures. For every vegetable there is an optimum soil temperature for
germination, and at that temperature the maximum number of seeds will
germinate and in less time than at any other temperature. A good guideline
figure that suits the majority of vegetables is 20C. But take note that there
are upper temperature limits for certain crops. Butterhead lettuce will not
germinate at temperatures above 25C, leeks and onions will not germinate
well above 21-24C and celery germinates best between 10-19C much higher
and it wont come through. Be careful of covering seed trays with glass or
polythene during hot sunny weather if the temperature of the compost goes
above 35-40C you will end up killing the seed. Consider using newspaper or a
polystyrene sheet over the glass in these situations.
You can buy a soil thermometer to check the temperature of your soil if youre
interested. Its probably best to measure the soil when its at its lowest which is
usually around nine or ten oclock in the morning and the standard dept of
measurement is 10 cm. Taking a series of daily temperatures and averaging
them will give you a more reliable figure in comparison to what the
temperature is on any one day. Alternatively you can log onto the Met Eireann
website and click on Latest Weather > Agricultural Data and there youll see
averaged weekly soil temperatures for a range of locations pick the one that
is nearest to you.
Say you want to grow a crop of French beans and wonder how early can you
sow them? We know that the minimum temperature required is 10-12C and
if we study the average soil temperatures for Dublin Airport you can see that
May is the month to pick perhaps towards the middle of the month for this
particular area.
Mean soil temperatures (10 cm) at Dublin Airport
Jan
Feb
Mar Apr May Jun
4.1
4.1
5.5
Jul
7.9 11.5 14.6 16.2
Aug
Sep
Oct
Nov Dec
15.4
13.0
9.7
6.6
4.8
37
Seed is sown at a dept that relates to the diameter of the seed see Table 2 in
the Appendix for details. You normally cover seed to make sure that it stays
moist for the requisite period of time after rainfall or irrigation but some seed
like celery or certain varieties of lettuce require light to germinate and is
normally sown on the surface of the compost.
Sowing under protection
The majority of seed thats sown under protection (glasshouse or polythene
tunnel) is now grown in modules essentially a tray with individual compartments
using special compost that is disease and weed free. The cells are normally
single seeded but crops like scallions and onions can be multi-seeded.
You may get a check to growth if plants raised under protection are planted
straight out into their final quarters. This is because there can be a big difference
in climatic conditions between the glasshouse and outdoors. To overcome this we
harden off our young plants to acclimatise them prior to planting out.
Commercial propagators will lay the trays out in a sheltered area beside the
glasshouse for a number of days before they are sent to the grower. You could
also place your plants in a frame and give increasing amounts of air to harden off.
The most usual way to ensure continuity of supply is to stagger your sowings
or plantings. To make things a bit easier with modular raised brassicas, make
one big sowing and plant out what you require when the plants are fit. Put
the remainder of the plants into a plastic bag and keep them in a fridge and
plant out at weekly intervals. Plants may be kept in the fridge for up to 3 weeks.
Outdoor plant bed
If you dont have a greenhouse, tunnel or frames you can raise your plants in
a nursery bed outdoors. Outdoor seed beds would commonly be used for
raising brassicas, leeks and lettuce.
Prepare your soil well as it needs to be in a fine condition for sowing seeds. If
lime is needed it should be applied during the previous winter. If a soil sample
result is not available the following fertilisers should be forked in: 50g per m2
of superphosphate, 30g per m2 sulphate of potash and 15g per m2 of sulphate
of ammonia. Seed is usually sown in rows known as drills.
38
When sowing brassicas a seed bed plant

population of 400 per m2 is recommended. A
spacing of 10x2.5 cm would achieve this. If a 10
cm drill width is too narrow, then suggest using
15x2.5 cm which will give a plant population of
266 per m2. Do not go below an in-row spacing
of 2.5 cm this is equivalent to 40 plants per
metre run. No thinning is required. Plant out
when the plants have reached the 3-5 true leaf
stage. Water before lifting if the soil is dry.
If slugs and snails are troublesome slug pellets
should be used. Cover outdoor beds with
netting to keep birds, cats and dogs away.
It takes from 5 to 8 weeks to produce a brassica
transplant depending on the time of year. Under
protection it typically takes 6 weeks to produce
a transplant.
Kinking of stem (hockey

stick) of a sprout plant raised
outdoors. Kinking seems to
be due to anything that
makes the plant grow too
quickly, too etiolated: heat,
fertilizer, lack of light but can
be varietal; some varieties
seem to suffer regularly and
others do not.
Direct drilled crops

If sowing outdoors it is important that you prepare the ground well by forking
and raking to produce a fine tilth. For direct drilled crops its critical to sow your
seeds at an even dept that leads to even emergence, as you want to end up
with a uniformly sized crop. Its not easy to make a drill by hand that has an
even dept all the way along its length. Seed that is deeply buried will emerge
later in comparison to more shallowly sown seed and this difference is
maintained right through to harvest. To get over this you can make a wooden
sowing frame to help you control the dept of sowing.
39
Once seed is sown it requires water to germinate, supplied from either rainfall
or irrigation. Uneven emergence can also be caused by an irregular water supply
when the crop is germinating. Another problem that can arise with outdoor
sowings, especially on poorly structured soils, is soil capping if the rainfall or
irrigation following sowing is very heavy. This is where the very fine particles
are washed into the spaces between the larger particles and the soil is said to
have slumped. If it then dries out, a hard surface crust develops, which can
physically prevent the germinating seed from emerging. One way around this
problem is to water the bottom of the drill before sowing your seed. If the soil
does cap keep the soil damp with frequent light applications of water to allow
the crop to emerge. Always use a watering can with a fine rose when watering
seed or seedlings.
Even emergence means an even end product.
Vegetable Storage
Some vegetables wont store, go over quickly and have to be eaten fresh.
Examples include butterhead lettuce, scallions and spinach. They can be kept in
a fridge for a week or two but after that will need to be consumed. Onions
and garlic on the other hand are natural storage organs with papery outer skins
protecting the fleshy inner scales from physical damage and drying out.
Another example is haricot beans where the beans are allowed to mature on
the plant to dry off the individual seeds, which can then be stored in jars.
A lot of our winter vegetables mainly brassicas, leeks and root crops are
best stored where they are growing, in the ground. The weather is cold enough
from November to March to restrict growth and development think of it as
natural refrigeration. However we need to be mindful of severe frosts causing
40
damage. Winter brassicas are normally not protected but in colder parts of the
country it may be worthwhile to earth up root crops with soil. Better still would
be to cover them with a layer of straw, bracken or leaves.
Crops grown for winter consumption need to be planted or sown early enough
to allow them reach the desirable size before growth ceases but late enough
so as to prevent them getting too large and in the case of root crops too woody
and tough. For example a good time to drill carrots for overwintering would be
from mid May to mid June.
Building a clamp was the old way of storing root crops through the winter but
is not much used nowadays. A clamp is where the crop was harvested in late
autumn, put in a pile outdoors and covered by straw and clay. The idea is that
the covering will keep the temperature of the roots from going too high or
too low and maintain them at a high humidity. If you want to try one, pick the
coolest part of the garden and make a long stack of roots about a metre wide
and high, cover with 15 cm of straw and top that off with 15 cm of soil. Dig the
soil from around the sides of the clamp so as to provide a degree of drainage.
Keep an eye out for rats to prevent or minimise spoilage.
Potatoes are a root crop that needs to be lifted and stored by the end of
October at the latest. They require to be stored in a cool, dark, frost-fee shed.
If light gets at the tubers they develop poisonous alkaloids in the surface of
the tuber as they turn green in colour. Paper sacks that the commercial crop is
sold in, would be useful for storing the home saved crop as they allow it to
breath and prevents light damage. Potatoes are susceptible to frost but the
main problem for the gardener is keeping the temperature low enough; 4C is
an ideal storage temperature but hard to achieve. The higher the temperature
the greater the risk of storage rots and sprouting. The tubers will eventually
sprout if held for longer than their natural storage period but will sprout
prematurely if the storage temperature is too high. If this happens go through
the crop and remove the sprouts this will give you a few extra weeks storage.
The question is sometimes asked about leaving potatoes in the drills overwinter and whilst it is possible provided they are sufficiently insulated, its not
recommended as you may well end up with increased levels of slug attack and
rodent damage.
41
Onions are available all year round in the shops with most of the supply coming
from refrigerated stores where they are stored at 0-2C and 70-75% relative
humidity. These conditions are difficult to replicate at home but do your best
to store onions and garlic as cold as you can and as dry as you can. Onions will
store for several months at ambient temperatures in an unheated building a
north facing unused bedroom could be used. The key point to remember is that
dormancy in onions or garlic will quickly be broken by water or moisture on the
bulb hence the reason to keep them dry and also the reason for not storing
them in any sort of plastic bag.
Successful onion storage begins at sowing time by choosing a variety that has
good storage qualities. Onions from sets will not store as well as those from
seed. The best of the seed varieties (e.g. Hyfort F1, or Vision F1) will store until
March or April before sprouting becomes a problem.
Equally important is ensuring that the crop is harvested correctly. When the
tops fall over on the plants in August or September, sprout inhibitors are
produced in the leaves that are translocated down to the bulb and its for this
reason that the leaves are dried on the bulb. When most of the tops have
fallen over lift the crop and dry off, ideally in a glasshouse. Its essential to seal
the neck of the bulb by ensuring that the leaves are completely dry before
removing them. The bulbs can be tied into onion ropes or put into a net bag
and hung up. Alternatively they can be put into stackable slatted wooden
trays going to a maximum of two deep in the tray. The main idea is to have
a flow of air around the bulbs to remove the moisture thats continually
produced by respiration.
Finally just to say that the invention of refrigeration has revolutionised
vegetable storage. With freezers now commonplace in most homes, this is
becoming a increasingly popular way to store home grown veg and also a
handy way of dealing with the inevitable gluts.
42
Asparagus
Asparagus is a perennial vegetable thats grown for its edible young shoots
(spears) that appear in late spring. A well drained site is essential for this crop.
As asparagus will remain in the same place for as long as 20 years the site
should be carefully dug over as deeply as possible taking care to remove all
perennial weeds such as scutch-grass, docks, etc. Plenty of farmyard manure or
bulky organic material should be well mixed with the soil during digging.
Asparagus is grown from seed or from one-year old crowns planted in March.
Either way the plants must be allowed to establish for 2 years before taking
your first harvest in year 3.
Sow seed in modules in January at 16-18C under glass. Plant out in late May
to early June in a staggered double row at a spacing of 45x30 cm, leaving
90 cm between rows. Plant in a 10 cm deep depression and as the plants grow
gradually level off the bed by the end of the first seasons growth.
The easier alternative is to buy in 1 year old crowns and plant in March taking
care to space out the roots in all directions and covering with soil to a depth of
10 cm.
A light cut can be taken in the second year but the best advice is not to take
the first harvest until the third year and dont cut beyond May 23. The harvest
period in subsequent years can extend over a 6-8 week period from mid April
to mid June. Cut the stems about 2.5 cm below ground level when the spears
are 13-18 cm tall.
When the foliage has turned yellow in the autumn cut it down to within 2.5 cm
of soil level. Top-dressings of farmyard manure should be given each autumn
and supplemented in spring with a dressing of artificial.
Varieties: Backlim F1, Gijnlim F1, Millenium F1
Diseases: rust, wilt
Pests: slugs
43
Beans, Broad
Broad or fava beans are a hardy leguminous crop that
can be sown in the autumn or spring. There are three
main types Seville, Longpods and Winsors and can be
further divided on the basis of seed colour, green or
white. Seville (e.g. Aquadulce) are the hardiest suitable
for overwintering. Longpods have eight seeds per pod
while Winsors have four seeds in shorter, wider pods. A
fourth type is the Dwarf or Fan-podded (e.g. The Sutton)
which are bushy, short plants that mature quickly.
The very earliest crop can be sown in late October or November, weather
permitting. The two varieties recommended for overwintering are Aquadulce
and The Sutton. Most of the varieties grow about 1.3 m tall and require some
sort of support but The Sutton is smaller at around 80 cm and is free standing.
The spring sown crop is drilled any time from February to May. For succession
sow the next batch when the first sowing reaches 8 cm in height.
The seed should be sown in staggered double lines, 23 cm apart each way. If
more than one double-row is to be grown allow 60-75 cm between them.
Where you want to add organic matter to the soil, open a trench 30 cm deep
and wide and add a layer of well-rotted manure or compost to the base and
mix with the soil to leave a trench 5 cm deep. Sow your beans and cover over
with the remaining soil.
To support the crop erect posts at either end of the drill and tighten a double
row of twine between them. Cut off the tops as soon as four clusters of flowers
have formed to ward off possible attack by the black bean aphid. They take
around 3 to 4 months to crop from a spring sowing and last for up to a
month. Pick the pods when quite young before the scar on the pod turns
black; if left too long the beans will be tough to eat. At the end of the harvest
cut the stems down at base level to leave the roots in the ground to allow the
nitrogen containing root nodules to rot down for the next crop.
Varieties: Express, Imperial Green Longpod, Aquadulce, Jubilee Hysor,
The Sutton
Pests: black bean aphid, pea and bean weevil, crows
Diseases: chocolate spot (Botrytis), rust
44
Beans, Dwarf, French or Kidney

This versatile vegetable can be harvested as immature green pods (green beans), left
grow on to a half ripe stage where the pods can be shelled like peas (flageolet) or let
mature completely to dried beans (haricot). There are two forms: bush and climbing.
NB: take note that beans at the flageolet stage (especially if they are a bit
overmature) can be poisonous if eaten raw. Cooking renders them completely
safe to consume.
French Beans are sensitive to cold temperatures and exposure, so chose a warm,
sheltered spot for them. They require a minimum soil temperature of 10-12C
for germination. In early districts the first sowing may be made early in May and
in late districts about the third week of that month. Further sowings can be
made to the end of June. Open lines 5 cm deep and 45 cm apart. Place the seeds
5-10 cm apart in the drill. An early sowing may be made around mid April in a
glasshouse by single seeding 5 cm pots for transplanting out in May when the
plants are about 8 cm tall. This early planting should be covered by fleece to
protect against late frosts or cold wind. French beans take about 9-10 weeks
from sowing to mature. Pick every two to three days to keep the plants
productive and to maintain quality by preventing seed development. Outdoor
crops can be harvested from July to October.
Commercial crops of French beans are always produced under glass using
climbing varieties. Climbing varieties are more productive than bush varieties
and especially so when grown under protection. For indoor production start
off the plants in 5 cm pots and plant out after about 3 weeks when 8 cm high.
Plant in double rows 60 cm apart, with 25-30 cm spacing between the plants in
the row. Allow 1.5 m for the paths between the double rows. The crop is grown
up twines supported on overhead wires 2 m from the ground. The stem should
be allowed to grow along the wire for a metre before being stopped. It takes
about 8 weeks for the first pods to be ready for harvest.
Bush varieties: The Prince, Nomad, Delinel
Climbing varieties: Cobra, Emerite
Pests: black bean aphid, slugs
Diseases: halo blight, root rot
45
Beans, Runner
More popular in the UK than Ireland in the
supermarkets in any case this is another example of a
half hardy vegetable which cannot be sown too early.
The runner bean is not only a nutritious vegetable, but
also an ornamental plant for growing against a fence
or wall, or to form a screen for an unsightly corner. It is
a climbing plant that will twist itself around a string or
a pole.
The seed is sown from mid May to mid June in double
rows. Sturdy supports are required, such as 2.5 m
bamboo canes, one per plant, that are arranged in a
tent like fashion secured at the top with a horizontal bar. The seeds are sown 5
cm deep, 30 cm apart, in rows 60 cm apart. Alternatively make a wigwam out of
6 or 7 poles with a plant per pole. One sowing is usually sufficient.
Twist the young shoots around the cane to encourage them to climb. When they
reach the top of the support pinch out the top of the plant to prevent it
becoming top-heavy. From the flowering stage on make sure to water your
plants in dry periods as this will help the flowers to set. Regular picking of the
crop will also encourage more pods to develop. Runner beans will crop from
mid July to mid October.
Varieties: Scarlet Emperor, Desiree, Kelvedon Marvel, Red Rum, Lady Di
Pests: black bean aphid
Diseases: halo blight, root rot
46
Beetroot
This is an easy crop to grow and will succeed on most
soils. There are two types long and the more popular
round or globe shaped. What you get in the seed
packet are clusters or dried seed heads that may
contain up to 3 seeds, unless you have purchased a
monogerm variety thats been bred to produce one
seed per cluster.
Beetroot is high in
folate, manganese
and fibre.
Seed may be sown from April to the end of June to

crop from July to March. For earlier sowing in March
use one of the bolt resistant varieties such as
Bolthardy. Cover that sowing with fleece to get it to
crop in early June.
The drills should be 25 cm apart and the seed sown

every 4 cm about 2.5 cm deep. Start lifting the roots as they are needed when
around 5 cm in diameter this gives the remaining crop more space to develop.
The crop is not fully frost hardy, so unless you are in a mild area, it is advisable
to cover them with 15 cm of straw sometime in November. Alternatively cover
with a double layer of fleece.
Varieties: Boltardy, Detroit 2, Burpees Golden, Pablo
F1, Red Ace F1
Pests: mangold fly (leaf miner), black bean aphid, beet
flea beetle
Diseases: leaf spot (Ramularia), scab
Two plants from

one seed.
47
A Guide to Brassicas
Crop
Sow seed
Spring
Third
cabbage week
July
Plant out
Varieties
Comments
30
30
March (Greens) Myatts

April-May
Offenham
(Hearted)
Compacta,
Pyramid F1
Sennen F1
25
25
January
March
(unhearted)
Wintergreen Sow in situ
March
April
45
45
June July
Caramba F1
Pyramid F1
Hispi F1
Greyhound
Caraflex F1
May June
45
45
July
September
Caramba F1 Watch out for

Caraflex F1 aphids and
Duchy F1
caterpillar in
the summer
period
Autumn May June June July

cabbage
45
45
September
October
Pyramid F1
Duchy F1
Caraflex F1
Fertiliser side
dressing as
above in July.
45
45
October
December
Pyramid F1
Duncan F1
Do not top
dress winter
Yorks
Spring
greens
Mid-Sept
early
October
Row Plant For use

Width Width
cm
cm
August
(direct drill)
Summer February
cabbage (Frame or
modules)
March
May
(open
ground)
June July July

August
48
When spring
growth starts
apply a side
dressing of
Sulphate of
ammonia
or CAN at
30g/m2
York varieties
are less
prone to
bolting from
early sowing
than round
head
A Guide to Brassicas continued

Crop
Sow seed
Plant out
Row Plant For use

Width Width
cm
cm
Varieties
Comments
Savoy
End April
cabbage Early-mid
May
June
July
60
35
November
Tarvoy
December
January March
Follow early
potatoes
Brussels
sprouts
Early May
Mid May
Late May
Early June
60
60
Sept October
Oct November
Nov Dec
Dec March
Abacus F1
Maximus F1
Helemus F1
Doric F1
Exodus F1
Two side dressings

of sulphate of
ammonia or CAN
at 30g/m2
March
60
45
June July
May to
early June
60
50
August
Nautilus F1 Water well

Nessie F1
after planting
Gipsy F1
to avoid
buttoning
Autumn
Late April/ June July
cauliflower June
20
60
60
September
November
Nessie F1
Skywalker F1
Belot F1
Winter
May/
July
cauliflower early June
75
75
70
70
January
February
March June
Miracle F1 January February

Medallion F1 production only
Aalsmeer
for coastal
districts
March
Early April
Mid April
Late April
Summer
Mid
cauliflower October
(frame)
March/
April
Broccoli
Calabrese
MidMid-April
February early
early June August
30
45
15
30
July November
Aquiles F1 Broccoli does

Ironman F1 not require a
Parthenon, lot of N
Green
Magic F1
Kale
April
May
60
45
Nov April
Bornic F1
Reflex f1
Sprouting
broccoli
April May May July

May
July
60
60
45
60
July- October
February - May
Summer
Purple,
Rudolf,
Red Arrow
June - July
New varieties
increase season
of harvest
49
Brassicas
Brassicas are an enormously versatile family covering the common or garden
vegetables like cabbage, cauliflower, broccoli, sprouts and swedes to the more
exotic rocket, mizuna and pak choi. A guide to the cultivation of these crops is
set out in tabular form and from this a selection of sowings may be made to suit
your requirements. Most brassicas are transplanted but some like swede, turnip,
radish and rocket are direct drilled.
Pests: cabbage root fly, mealy aphid, peach potato aphid, caterpillar, pigeon
Diseases: ring spot, dark leaf spot (Alternaria), white blister, downy mildew,
powdory mildew, club root, black rot (Xanthomonas)
Broccoli (calabrese)
This popular vegetable which only began to be
grown in Ireland from about 1980 is easy to
grow and can be harvested from July into
November from mid February to early June
sowings. The main harvest comes from a large
centre head, but once that is removed you can
get a second harvest from side shoot
production depending on variety. The wider the
spacing the greater the number of side shoots produced.
Ideally this crop is sown in modules as bare root transplants may induce
buttoning (production of a small premature head). It could also be direct drilled
and thinned out to the required spacing.
Broccoli is grown at a number of different spacings depending on the size of the
centre head required but the overall yield doesnt vary from plant populations
from 5 to 100 plants per m2. The suggested spacing of 30x15 cm is equal to 22
plants per m2 which gives a nice balance between centre head and side shoot
production. If you want a larger centre head try using a 45x30 cm spacing.
50
Broccoli is the least hardy of the brassicas so dont plant out before about
8 April otherwise blindness in plants (death of the growing point) can occur.
The latest you can plant broccoli is up to the first week in August. Broccoli has
quite a low demand for nitrogen, so an application of manure or compost
should suffice especially for crops maturing in the August to October period.
Otherwise apply 15g per m2 at planting and repeat a month after planting. For
early crops increase the rate to 50g per m2 applied in two splits.
During hot weather you may find some of the beads on heads that are close to
harvest opening up and turning yellow. Certain varieties are more prone to this
problem than others but is worst where the heads are slightly over mature so
harvest on time.
Broccoli, Sprouting
This is a hardy crop that was grown to fill in
when there wasnt much else around in the
vegetable garden in the spring time. However
new varieties have been developed that allow
for a greatly extended season of production.
Depending on the variety chosen sprouting
broccoli can be harvested from July to May.
For late summer to autumn production through to spring sow from April to
June and transplant from May to July. For the over wintered crop it is essential
to protect your plants from pigeon damage by netting or black thread. The
plants may need to be staked as they are tall growing.
Come harvest time a centre head develops and side shoots or spears grow out
from the main stem below the centre head. Both the centre head and side shoots
should be harvested before the tiny purple flowers open out to a yellow colour.
A succession of pickings can be made as long as side shoots continue to develop.
51
Brussels sprouts
Plant breeders have done a number of favours for
this much maligned vegetable the season now
stretches from September to March, the sprouts are
easier to pick and are better flavoured and the
development of hybrids has rendered blown sprouts
a thing of the past. However sprouts can be a difficult
enough crop for the amateur to grow for a few
reasons. The crop including the bit you eat can be
prone to a variety of pests and diseases which the
professional grower can counter by using a range of
chemicals that are not available to gardeners.
Sprout varieties can be roughly divided into early, mid
season and late, spanning the months mid-August to
October, October to December and December to March. They need a long
season of growth and start off with being propagated as bare root transplants
or in modules. The following table is a guide to sowing and planting dates.
Sow
Plant
Harvest
Late February (frame)

Mid Late March
Early April
Mid April
Late April
Mid Late April

Early May
Mid May
Late May
Early June
August September
September October
October November
November December
December March
The main sowing period is March April with the bulk of the planting taking
place in May and up to the end of the first week in June. You can plant later in
June but yields will reduce.
Succession in sprouts derives from using different planting dates combined with
different varieties. One possible suggestion to use Maximus or Helemus planted
in mid May for October to December period followed by Doric or Petrus in early
June for December to February; but there are lots of other varieties and timings
to pick from.
52
Sprouts develop naturally from the base of the stem to the top and most
gardeners will harvest them on a cut and come again basis. However
commercial crops are sometimes stopped by removing the growing point to
allow the sprouts to mature evenly for machine harvest. This is done when the
bottom sprouts are a centimetre in diameter. You might consider using this
technique if you were growing a crop for freezing but in general stopping
confers no benefit to the gardener.
Plant spacing for sprouts varies from 2.8 to 3.7 per m2. Populations greater than
3.7 incurs the law of diminishing returns. Increasing your plant population
results in:
reduced sprout size on the stem

increased stem length
delayed maturity
increased uniformity of sprout development on the stem
In relation to these characteristics overall plant population has been found to be

more important than the spatial arrangement of the plants. The old traditional
spacing for sprouts was 90x90 cm which is too wide for the hybrid varieties that
are currently in use. For regular picking over of sprouts suggest using 60x60 cm
or 60x50 or 45 cm for a tighter spacing. If you are growing for freezing try out
a spacing of 50x50 cm, stop the crop and carry out a once-over harvest.
Sprouts have a high nitrogen requirement as you need to get height into the
plant for optimum yields. Apply 30g per m2 of sulphate of ammonia at planting,
and repeat a month later and again in July.
Start picking your sprouts when the bottom ones are between 2-4 cm in
diameter. The sprouts you buy in the shops are normally sold in two separate
size grades: 22-30 mm and 30-38 mm. The interval between picks is from 3-5
weeks and a single variety can crop for up to 4-5 months. A single plant will
yield 60-70 sprouts or about a kilogram in weight.
Aphids can be a problem with this crop if they are allowed to establish within
the buttons. They tend to start to build up in July with large populations
developing by early autumn. As there are no effective aphicides available to
the amateur market the plants should be covered with fleece from July to
53
October. Slugs can also be troublesome as they will climb up the plant to feed
on the sprouts. Apply 3 applications of pellets during the summer to autumn
period. The main diseases on sprouts are ring spot and white blister.
Cabbage
Cabbage is a crop that can be harvested
virtually all year round. There are several
different types round headed (ballhead),
pointed (York), Savoy (winter maturing), red
cabbage, white cabbage (for coleslaw) and
winter cabbage (Tundra type). Cabbage is
planted at a variety of spacings depending on
variety. York cabbage can be grown 12 months
of the year but during the winter months it is
harvested as greens, which is unhearted heads of cabbage.
Cabbage requires generous feeding but the quantity and the kind of fertiliser
varies with the season. Autumn planted cabbages which have to withstand the
rigours of winter are given little nitrogen but relatively high potash. With the
advent of fine weather in the spring nitrogen is given as light top-dressings. For
cabbage planted in September-October give a light dressing of farmyard
manure or compost. As soon as growth commences in spring give 30g per m2
of calcium ammonium nitrate (CAN) or sulphate of ammonia and repeat three
weeks later. Compound fertilisers such as 0:7:30 or 0:10:20 are suitable for
autumn planted crops while 8:5:18 + B is suitable for spring or summer sown
crops. For summer and autumn maturing cabbages farmyard manure or
compost is very desirable supplemented with 30g per m2 sulphate of ammonia,
plus a top dressing of 30g if necessary.
Cauliflower
It is possible to have cauliflowers in season during most of the year but take
note that production in the January-February period is usually only possible in
mild coastal locations. Careful selection of varieties and sowing and
54
transplanting dates will go a long way towards

successional cropping. Weather conditions will
influence harvesting dates.
A general rule of thumb is that plant spacing
increases as the season progresses. This is
because a larger plant size is required to
produce a head of cauliflower in the depths of
winter than an early crop in June.
Early summer cauliflower for cutting during June and early July are sown either
in cold frames in mid October or under glass in January. They are planted out in
warm well-manured ground in March as soon as weather conditions allow, at a
spacing of 60 x 45 cm. This crop is particularly susceptible to buttoning, which is
where a small curd (edible white portion) forms prematurely caused by a check
to growth. The crop must be kept growing to produce a big frame so make sure
to water during dry spells.
Summer cauliflower for cutting from mid July to August can be sown in MarchApril for May planting.
Autumn cauliflower is the easiest to grow and gives the biggest yield. Seed
should be sown from late April to June for transplanting from June to about
20 July. The plants should be planted out at 60 cm square 5-7 weeks after
sowing. It is a mistake to leave them too long in the seed-bed or modules as this
may lead to buttoning.
Winter cauliflower may be had in succession from December to May by planting
a number of varieties. Development of the heads is greatly influenced by the
prevailing weather mild spells may cause rapid maturing while cold, wet
weather with little sun will delay development. Hence, it may be difficult to
accurately time the harvesting of this vegetable. Crops that mature in the January
to February period can only be grown in the milder coastal areas of the country.
Commercial crops of winter cauliflower traditionally follow early potatoes.
Where winter cauliflower follows an early potato crop, 90g per m2 of a
compound vegetable fertiliser should be given. Nitrogen top-dressings in the
early spring are necessary for the late maturing kinds (February-May).
55
Carrots
Carrots can be grown on a range of soils from heavy
to light but the majority of the commercial crops are
grown on medium to light soils. Nairobi is possibly
the variety to use for heavy soils. They can be
produced outdoors from July to March. The best
place to store carrots for winter and spring use is in
the ground where they are grown. However they are
quite susceptible to frost so spread some soil over the
tops in November or cover with a double layer of
fleece. In the colder areas of the country cover the
beds with 25-30 cm of loose straw. It might be no
harm to apply some slug pellets prior to strawing
down. The use of leaves would be a suitable alternative to straw.
There are several different types (root shapes) of carrots such as Amsterdam
and Nantes and plant breeders have used them to produce hybrids, which is
now the dominant type on the supermarket shelf.
The early crop is sown in February/March for July production. The main crop is
normally sown in May. A late sowing of an early variety can be made in June
to give you a tender tasting crop in about 12 weeks. Seed may be sown in lines
15 cm apart on the flat at a dept of 1-2 cm. Carrots are difficult to sow by hand
as the seed is small, but try to sow thinly so as to avoid thinning; otherwise thin
the resultant seedlings to 5-7 cm apart. One can get pelleted carrot seed which
although more expensive is easier to sow evenly by hand.
Varieties
Early: Mokum F1, Trevor F1
Maincrop: Ulyses F1, Nairobi F1, Kingston F1, Flyaway F1
Pests: carrot fly, aphids, slugs
Diseases: cavity spot, Alternaria, Sclerotinia, scab
56
Celery
There are three types of celery green, self-blanching (SB) and trench. The old
fashioned trench celery is no longer favoured having being replaced by the
easier to grow self blanching and green varieties. Virtually all of the commercial
crop is now green celery. Trench celery was grown in rows but the self blanching
and green varieties are always grown on beds. In order to get self blanching
celery to blanch correctly it needs to be grown in a block at close spacing.
Blanching is the development of a light colour by the process of excluding light.
The main input to growing celery is water. A high level of fertility is also
necessary as you need to aim at maintaining continuous growth in order to
grow succulent sticks of celery. A heavy dressing of farmyard manure or compost
should be dug in and supplemented with artificial fertiliser if necessary.
Celery needs to be propagated and grown on under glass or polythene before
being planted out. Sow the seed in March or April on the top of a moist
compost and keep covered with polythene or glass until germinated in about
2 weeks. Grow on until large enough to handle (1 true leaf) and prick out into
trays at 3 cm square spacing. They could also be pricked singly into modules. It
takes 4-5 weeks from sowing to pricking off and a further 4-5 weeks from
pricking off to planting out.
The crop is transplanted out in May and June; a late crop can be planted up
to July 20 for harvest in November and December but this crop is a bit of a
gamble as it can be damaged by early frosts. Celery is normally planted on the
flat in beds, typically four rows across a bed, 28-30 cm square in a diamond
shape. A dressing of sulphate of ammonia at 30g per m2 may be given
pre-planting and topdress at about the 4 and 6 week stage with another
30g per m2.
Irrigate after planting and after topdressing to establish the plants and to wash
the fertiliser in. Copious watering should also be given during dry weather.
57
It might be no harm to sprinkle some slug pellets among the plants before
the crop leaves close in as slugs can move up into the developing celery head
and consequently be difficult to remove. The crop is in season from August
to November.
Varieties: Galaxy (SB), Loretta F1 (SB), Victoria F1 (green), Tango (green)
Pests: carrot fly, aphids, slugs, celery fly
Diseases: celery leaf spot (Septoria), Pythium root rot, pink rot
Disorder: black heart (calcium deficiency)
Chicory
Chicory can be grown on any light fertile soil provided the site is deeply worked
and heavily manured. Farmyard manure, potash and phosphates should be
incorporated in the soil during the autumn in preparation for seed sowing
towards the end of May or early June. Seed is sown in lines 30 cm apart and 1 cm
deep; the plants are later thinned to 20 cm apart.
By October the roots will be fully grown and may be lifted for blanching. Those
not needed at once should be heeled in temporarily.
Forcing is done by introducing medium-sized roots of about 2.5 cm in diameter
into the forcing shed or glasshouse. The roots are cut to a uniform length of
20 cm and placed in an upright position in rows 5 cm apart and 2.5 cm apart in
the rows. After watering they are covered with light soil, sand, or peat to a
depth of 17 cm so as to blanch the subsequent growth. If a suitable house is not
available a forcing bed may be prepared out of doors by erecting boards 23 cm
wide along its sides. The prepared roots are placed in position and after
watering are covered with suitable blanching material. Fermenting stable
manure, if available, may then be placed on top to speed up growth but if such
material cannot be obtained the bed should be covered with glass lights,
corrugated iron or other protective material. Some new varieties are now
available which can be forced without covering with soil.
Varieties: Witloof, Normato, Mitado, Tardivo.
58
Courgettes
Courgettes or zucchini are immature marrows which are
harvested when about 15 cm long or less. It is a frost
tender crop that is normally sown indoors in the latter half
of April, single seeded into small 8 cm pots. Heat (20C) is
desirable to get the seeds to chit (germinate) a process
that takes 2-3 days. If you wish to save on heated
propagation space, germinate the seeds in moist paper or
peat and when chitted prick off into pots. Grow on at
lower temperatures but frost protection must be provided. It takes about 4
weeks from sowing to planting out at the 2-3 true leaf stage. Plant out the last
week of May to the first week of June after the threat of frost has gone,
spacing the plants 80 cm apart each way or 90x75 cm to give a plant density of
about 1.5 plants per m2. If late frosts threaten cover the plants with fleece. They
can also be sown directly into the ground in June, using 2-3 seeds per station.
Courgettes have separate male and female flowers; you will see a small
undeveloped fruit at the base of the female flower. Early in the season you may
notice that the flowers are initially all male but later on settle into a pattern of
producing both types. If a plant is under stress (low light, cold or wet) it tends
to produce all male flowers. Pollination is carried out by flying insects.
Courgettes in good growing weather develop their fruit very rapidly and
should be picked over every 2-3 days. They will crop from mid July to October.
Varieties: Defender F1, El Greco F1, Firenze F1
Pests: slugs, aphid
Diseases: powdery mildew, Botrytis
Garlic
Garlic, a member of the onion family, is grown from cloves, not from seed. And
unlike most of its relatives, the bit you eat, the bulb, grows underground. There
are two types: hardneck and softneck. Hardnecks develop a stiff neck from the
flowering spike sometimes refereed to as a rocambole. Bulbs from this type are
frequently purple or pink in colour. The soft necks are usually white in colour
59
and store well. We import most of our garlic from

China and Spain.
The best crops are grown on light, free draining
soils. On heavier soils grow the crop on a raised
bed to improve drainage especially for the overwintered crops.
You can use ordinary shop garlic but as there are
Clove of Garlic.
many clones of garlic you may find you get better
results with named varieties purchased in a garden outlet. In addition shop
garlic is often treated with a growth regulator that will give poor sprouting
when planted out. Garlic needs exposure to cold temperatures (0-2 C for 1-2
months) to initiate bulbing this can happen during storage or post planting.
Garlic is a hardy vegetable that is either over-wintered or planted in early
spring. Plant in October-mid December for June/July harvest or in FebruaryMarch for July/August harvest. The bulb must be broken up into cloves for
planting, ideally 1.5 cm in diameter. Plant the cloves with the basal plate facing
downwards, 5 cm deep, in rows 20 cm apart with an in-row spacing of 10 cm.
Garlic is not a high nitrogen demander but does need irrigation during dry
spells. If any flower stems are produced, just snap them off to allow the plant
concentrate all its energy into the developing bulbs. Harvest the crop when
10% of the tops have fallen over or when the foliage just starts to turn yellow;
trim them with a shears to 15 cm, lift and tie together in bunches and hang in
light, airy, place to dry. Or else lay them on wire mesh in a glasshouse. After
about 2 weeks they should be sufficiently dry. The art of drying garlic is to
achieve tight, full cloves in the bulb with the leaves around the bulb and the
stem completely dry but not brittle. Store in a cool dry place can last up to ten
or eleven months.
Varieties: Arno, Cristo, Germidour, Purple Wight, Solent Wight
Pest and Diseases: as for onions but main problem is rust
60
Kale
Kale is one of the hardiest and also one of the most nutritious of vegetables but
has never taken off in the popularity stakes. However the newer varieties are
better flavoured than those of old. The leaves are the edible part and these
can be harvested individually, or the complete head can be harvested in one go.
Although its produced commercially from June to April, its still regarded as a
traditional winter crop available from November through to March. To cover
the June to April period five or six plantings will be required at approximately
monthly intervals from March to the end of July for the late crop; this will entail
sowing the crop in modules from January to June. Plant density for kale is in the
order of 3.7-4.5 per m2. So use a spacing of 60x45 cm for early and late crops
and 60x37 cm for the main crop.
Varieties: Bornick F1, Firbor F1, Reflex F1
Pests: aphid, caterpillar
Diseases: ring spot, white blister, largely resistant to club root
Kohlrabi
This underrated brassica vegetable is far more
popular on the continent than in these parts. It
originated in northern Europe in the fifteenth
century and its name comes from two German
words: kohl meaning cabbage and rabi meaning
turnip. The turnip-like globe of kohlrabi is actually
the swollen base of the stem, not the root. There
are green and purple versions.
Kohlrabi can be either direct drilled or sown into modules and planted out.
Sow from April to July in rows 30 cm apart with 20 cm in-row spacing. If sown
too early there is a risk of bolting and if going earlier into March sow in
modules under protection and plant out later. Sow every 3 weeks for
succession. Its a quick growing crop ready for harvest about 2 months after
61
sowing during the summer months; so keep the crop moving along during dry
spells by watering it. Harvest the crop when the bulb is between golf and
tennis ball size.
Varieties: Domino, Congo, Superschmelz
Pests: as for brassicas
Diseases: as for brassicas
Leek
One of the hardiest vegetables and often a valuable
substitute for onions, leeks are in season from
August to April. The edible part is the blanched
white lower portion of the stem and to achieve
this we plant into 15 cm holes in the ground that
gradually fill in as the season progresses. They can
also be deep planted using a trowel.
Bare root transplants.
This crop can be direct drilled or planted. Leeks sown directly suffer from the
same problem as direct drilled onions competition from weeds. So its
probably easier to sow into modules or use bare root transplants. Leeks are not
the easiest of plants to grow in modules and would recommend the easier
option of sowing into frames or open ground.
The early crop is sown in January under glass for planting out in April. The main
crop is sown in March in a frame or in an outdoor seed bed in drills 15 cm apart
using a seed rate of 75 per metre run. Leeks are quite slow growing in the early
stages and will take about 10 weeks before being large enough to transplant out
in May or June. The late crop can be sown from April to early May for
transplanting out in June July. Trim the leaves of the pulled plants and also the
roots to leave a pencil thick 12 cm long plant. Leeks will readily regrow new roots
from the base plate so dont be afraid to trim them back. They are put in rows 30
cm apart with 15 cm between the plants. Planting is done with a dibber making
a hole 15 cm deep. A single plant is dropped into the hole and watered in.
62
Varieties: Zermatt, Longbow, Porvite, Oarsman F1, Kenton F1, Bandit

Pests: thrips
Diseases: rust, white tip (Phytophthora), white rot, Fusarium foot rot
Legumes
Legumes are members of the Fabaceae family (formerly Leguminosae). They
include the peas and beans both of which have long been recognised as hugely
important to mankind. Important for two reasons they are a source of protein
in the human diet and most of them have an ability to fix nitrogen from the air.
Hence they have been in cultivation since near the dawn of modern agriculture
10,000 years ago.
Nitrogen fixation occurs when nitrogen fixing bacteria colonise the roots of
clover, peas and beans resulting in the formation of nodules. Here the bacteria
convert nitrogen gas in the soil air into nitrogen compounds utilisable by the
host plant in exchange for carbohydrates supplied to the bacteria. And when
the nodules break down they release their nitrogen for other crops.
Peas and broad beans are nodulated by a bacterium called Rhizobium
leguminosarum. This species is very common in European soils as it nodulates
the vetches which are wild relatives of peas and beans. On the other hand
French and runner beans originated in South America have no compatible
bacteria in European soils and have difficulty in fixing nitrogen. However it has
been found that they can nodulate on certain soils. To check for active nodules,
dig up some roots to look for nodules; if present cut them open and a pink
colour (due to iron compounds) means they are fixing nitrogen, no pink means
they are inactive. The other thing that causes a lack of fixation is high soil
nitrogen legumes will use soil nitrogen (from fertiliser or organic matter) in
preference to fixed nitrogen as the latter takes a lot more energy. To improve
nodulation on French and runner beans, its possible to buy inoculants to mix
with the seed prior to sowing.
63
Legumes
N fixing Pollination
Pea
Annual
Broad bean
Annual
French bean Annual
Germination Origin
Yes
Self pollinating Hypogeal
Europe
Yes
Bees
Europe
Little
Self pollination Epigeal
S America
Bees
S America
Runner bean Perennial Little
Hypogeal
Hypogeal
Lettuce
There are many different varieties of lettuce but there are two basic types:
those that are leafy and those that form heads. Butterhead, iceberg and cos
are examples of head forming lettuce. Lollo Rossa and oakleaf are just two
representatives of leafy lettuces that exhibit a range of shapes and colours.
Once mature, lettuce will not hold well; for succession make subsequent
sowings when seedlings of the previous sowing have just emerged.
Alternatively one can buy a packet of seed with a mixture of varieties with
differing maturity dates.
Lettuce is normally a transplanted crop but some of the leafy types can be direct
drilled. It can be sown in a seed bed or tray and transplanted as bare-root plants
but will establish better from modules. Take care when planting lettuce to
ensure that the module is planted level or slightly proud of the surface of the
soil deep planting may induce basal rots in the young plant.
Cos is a type of lettuce that produces upright oblong plants with a crisp inner
heart. The Little Gem variety is one of the earliest to mature in a more compact
frame. Seed may be sown from March to mid July in drills 23 cm apart and thin
out the seedlings to 23 cm apart.
Varieties: Little Gem, Little Gem Maureen, Pinokkio
Butterhead lettuce can be produced from June to October from sowings
made from March to mid August. Space the crop at 30 cm square. Because
lettuce is a perfectly circular crop, some savings in space can be made by
64
planting in a triangular pattern circles of 30 cm will fit into 30 cm rows and

27 cm in-row spacing.
Varieties: Cassandra, Roxy, Diana
Lettuce needs to be kept growing so water during dry spells and a rich,
moisture retentive soil will help in this regard. Farmyard manure or compost
may be used to enrich the soil and improve its moisture retaining capacity.
Pests: aphids, root aphid, slugs, caterpillars
Diseases: downy mildew, botrytis, bottom rot, ring spot, sclerotinia
Onion family
The Alliaceae or onion family is a very important food group that has been in
cultivation for thousands of years. Members include onions, scallions, shallots,
garlic, chives and leeks.
Most vegetables are dicots meaning that they have two seed leaves or cotyledons.
But the onion family and sweetcorn are monocots possessing just one seed leaf.
The diagram below shows the seedling growth stages of an Allium.
Chitting is the visible start of the germination process after the seed has
imbibed water. The seed coat breaks and produces an initial root followed
shortly by the cotyledon. The solitary seed leaf or cotyledon arches up through
the ground in the shape of a loop and then gradually straightens itself out to
reach the crook or flag leaf stage. Shortly after the crook stage youll notice a
second leaf coming through this is the first true leaf (arrowed), which looks
65
identical to the cotyledon. As more true leaves are developed the cotyledon
begins to wither and fade away. It takes about a month from sowing to the
first true leaf stage.
The initial emergence and growth of an onion crop can be slow due to low
temperatures. As the days lengthen and the weather gets warmer new leaves
are produced and the plant gets bigger. But at a certain stage leaf production
stops and the plant switches over to bulbing. This is where the leaf bases begin
to swell into fleshy scale leaves that go to form the familiar bulb. The
environmental trigger for this change in development is day length. For spring
sown varieties this equates to a day length of 16 hours which occurs in June. It
follows then that the more leaves we have before the switch-over takes place
the bigger your bulb will be. And this is the reason why we need to sow our
crop in early spring or by starting them off in modules under glass. And it is
also the reason why sets are so handy they establish and grow away quickly.
Sets are very small onion bulbs that are produced by late sowing and close
spacing. By sowing late only a few leaves are formed before the switch-over to
bulbing takes place and hence small bulbs are produced. These are then stored
over-winter for planting in the following year.
Bulbing in the field becomes obvious when you notice the base of the onion
beginning to swell during July and warm temperatures at this time greatly
helps the process.
Onions, shallots and garlic all share the same
ripening process. When the tops start to topple
over, its a sign that the crop is maturing and
getting close to harvest. With the exception of
garlic leave them for 2 weeks to complete the
process and then lift with a fork. To store them
successfully the crop has to be dried. If the
Harvesting windrowed
weather is warm and dry the drying can take place
onions in Co Dublin.
outside; get the crop up off the ground onto
something like suspended chicken wire to allow air to circulate and cover with
plastic if rain threatens. But better still, bring them into a glasshouse or plastic
tunnel and spread on staging for 2-3 weeks until the necks are completely dry.
66
Any thick necked onions can be set aside for immediate use. Twist off the
foliage and store the bulbs in trays, net bags or tie into onion ropes for hanging
from rafters.
When applying nitrogen to onions it is normally split 50:50. With direct drilled
onions apply half at sowing and the other half at the first true leaf stage. With
sets and planted onions apply the first split at planting and the second about
a month later. The latest date for nitrogen application is mid June.
Pests: thrips (mainly leek), bean seed fly (scallion)
Diseases: downy mildew (onion), rust (mainly leek), Botrytis leaf spot (onion),
Botrytis neck rot (onion), white rot, white tip (leek), Cladosporium leaf
spot (onion)
Onion, Potato
The potato onion bulbs should be planted in well manured ground early in
February. Plant in rows 30 cm apart and 23 cm between the plants in the rows.
Cover the bulbs to rather more than half their depth. Early in August, as the
bulbs are ripening, they should be pulled up and left on the surface to dry.
When thoroughly dry, they should be stored in a cool dry place. Reserve a
quantity of the smaller, well-ripened bulbs for planting in the following spring.
Planting stock of this type of onion is not commonly available.
Onion, Seed
We can grow onions perfectly well in Ireland but
the problem for the commercial grower is to get a
couple of dry, fine weeks in September to harvest
the crop. Drilled onions need a long season to
provide yield and good bulbing development for
harvesting in early autumn. But the advantage of
seed onions over sets is they will store for longer,
can have less problems with disease and theres a
greater choice of varieties.
Direct drilled onions.
67
Bull Necks
The formation of an unusually thick neck on an onion is called a bull neck. It
is difficult to dry these sorts of onion and as a consequence dont store well. The
most common reason for this disorder is too much nitrogen either from too
much manure or fertiliser, especially if topdressed too late. It tends to be worse
in a wet year. It may also be related to a poor bulbing response brought on by
low light levels and high rainfall. Late sown crops, late varieties and sets are the
most prone. Use bull neck onions immediately and dont bother to store.
Sow the crop from mid February to mid March with the very latest date being
the first week in April. For late sown crops apply irrigation if the weather is dry
to get the crop off to a flying start.
Most commercial crops are spaced to give a plant density of about 55 per m2
this gives a high percentage of bulbs in the pre-pack size grade of 50-70 mm.
Plant populations can vary from 25 to about 85 per square metre depending on
the size grade required. In respect of size, the greater the density the smaller
the bulb, and visa-versa. So space your crop accordingly to your own
specifications but dont go beyond 30 cm row widths. Some sample spacings
are shown in the accompanying box using 25 cm rows as standard.
Spacing cm
Density per m2
25 x 5
25 x 6
25 x 7
25 x 8
25 x 10
25 x 12
25 x 15
80
67
57
50
40
33
27
As onions are a slow crop to develop from seed and complete poorly with weeds
it is imperative that you keep the crop well weeded throughout the season.
68
As an alternative to direct drilling, you can propagate your onions in modules

under protection for planting out at a later stage. This method is well suited to
the gardener who prefers to use seed to sets. Sow 5-6 seeds per cell between
late January to mid February and germinate on a warm bench if possible. Once
germinated the modules can be grown on in a glasshouse or polythene tunnel.
Plant out in early to mid April at a spacing of 30x30 cm. The individual plants
look far too close together but youll be surprised at how they are able to
elbow each other out of the way as the season progresses.
The number of seed/seedlings per cell has a major influence on the eventual
size of onions produced. A seeding rate of 5 per cell will produce a lot of onions
in the 60-80 mm size grade; if you up the rate to 8 or 9 per cell you will get a
high proportion of 40-60 mm grade.
Varieties: Golden Bear F1, Hyton F1, Hygro F1, Hyfort F1, Vision F1, Red Baron
Onion, Sets
The easiest way to grow onions is by planting sets. These are small immature
bulbs specially produced for planting. The advantage of sets over seed is they
are quicker to establish and hence more accommodating in relation to time of
planting, easier to weed and mature earlier. Plant in March to mid April but the
season can extend from February to the end of April at a push. Ensure that late
planted sets are watered if the weather is dry to make sure they get off to a
rapid start. Spacing for sets is identical to spacing for seed onions so consult
that section. However a common spacing is rows 23 cm apart with sets 10 cm
along the row (43 per m2). Use a trowel to plant sets about 2.5 cm deep rather
than just pushing them into the soil, as they may push up out of the ground
when the roots start to grow. If you plant them just covered with soil it will
stop birds from rooting them up.
Sets can also be planted in the autumn for an over-wintered crop maturing in
July. Plant in the first week of October.
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Sets for the commercial market are sold in four size grades: 10-14 mm, 14-17
mm, 17-21 mm and 21-23 mm. The very smallest grade can lack vigour and the
very largest grade can be more prone to bolting. The ideal size is 14-21 mm.
Set onions normally mature in August. Onions from sets do not store as long as
onions from seed. They will store satisfactorily until about January, after which
time they start to sprout.
Varieties:
Spring: Stuttgarter Riesen, Sturon, Setton, Hercules F1, Centurion F1, Red Baron
Autumn: Shakespeare, Troy
Grow your own sets
Just for the fun of it try growing your own sets. You are looking to grow a set
somewhere between 14 to 21 mm in diameter, so correct spacing of the seed is
critical. Ideally grow them in a glasshouse or polythene tunnel. If grown outdoors
you will need to bring the seed trays indoors at the end of July to dry them off.
Variety: Sturon
Sow: second week May in a seed tray or suitably sized module
Spacing: 3x3 cm
Grow until the end of July and then stop watering to dry off the plants. In early
September top and tail the dried sets with a scissors and store in a cardboard
box placed in a cool dry place for winter storage.
Onion, Shallots
A shallot is a small onion, that when planted grows to give a small cluster of
bulbs at harvest time they will multiply up about 8-10 fold.
Shallots are quite hardy and can be planted in February or March 15 cm apart,
in lines 30 cm apart. Plant with a trowel, leaving just the tips of the bulbs visible.
When the leaves topple over and begin to die back sometime during July or
August, the clumps should be pulled up and left on the surface to dry. When
thoroughly dry, they can be broken up and stored in a cool dry place. All
the bulbs should not be used in autumn or winter; a quantity of the smaller,
well-ripened ones should be kept back for planting in the following spring.
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Shallots can also be raised from seed, with each giving rise to a single shallot. Sow
in March or April in drills 10 cm apart with seeds spaced 4 cm apart in the drill; you
require about 250 seeds per m2.
Varieties: Golden Gourmet, Matador F1
Onion, Salad
Salad onions or scallions are a direct drilled onion crop sown quite thickly and
harvested immature when they are about pencil thickness for use in salads. They
are produced commercially from outdoor production from April to November
and imports from Mexico and Egypt supply the winter to early spring period.
Sow from February to July for cropping from June to November and the over
wintered crop is sown during the last 2 weeks in August to the first week of
September for cropping from April to June. The early spring sowings can be
covered with fleece to ensure a late May to early June harvest.
The recommended density is around
320 seeds per m2. You can use row
spacings down to 10 cm but using a
spacing of 15 cm means a seed rate
of 48 per metre run or a seed
approximately every 2 cm.
There are two types of onion sown
as salad onion. The old standard
Allium cepa White Lisbon has been
Four row air drill sowing onions.
in cultivation since the late 1800s
and is an excellent garden variety. There is a selection of it called White Lisbon
Winter Hardy that is more suited to overwintering but more prone to bulbing
in the spring. The newer Allium fistulosum or Japanese bunching onion has a
more upright growth habit to White Lisbon, freer from bulbing but not suited
to over winter production. Also not quite as good to eat.
Varieties:
Allium cepa: White Lisbon, White Lisbon Winter Hardy, Lilia, Ramrod
Allium fistulosum: Savel, Green Banner, Ishikura
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Parsnips
Parsnips are a root crop that will grow in a wide range of soils, more tolerant
of heavy soils than carrots, and can be harvested from August through until
March. Sowings are direct drilled from March to May. The March sowing can be
covered with fleece for a mid July harvest.
Prior to sowing the surface should be forked over to a depth of about 10 cm and
raked free of stones and clods. The seed should be sown in drills 30 cm apart
and 15 cm apart in the drill, sowing 2-3 seeds per station. This spacing equals a
plant population of 22 per sq m giving you a medium sized root. For larger
roots go up to 30x20 cm. They will take from 2 4 weeks to germinate
depending on the weather. Thin to one plant per station. Parsnips are one of
the hardiest of vegetables and can be left in the ground during the winter,
digging them as required.
Varieties: Cobham Improved, Gladiator F1, Javelin F1, Countess F1.
Pests: carrot fly
Diseases: canker, various leaf spotting diseases
Peas
Peas are one of the most ancient and nutritious vegetables. There are two types
round and wrinkled seeded in the dried form. The round are hardier and
used for early and late crops and wrinkled are less hardy and generally sweeter.
Sow from March to June, every two weeks for succession if required, in flat
bottomed drills 5 cm deep, 15 cm wide, spacing the seeds roughly every 5 cm
apart. Allow 90 cm between the rows.
On poor soil, where it is necessary to apply manure at the time of sowing, a
trench should be opened 30 cm wide, and of the same depth, in which a layer
of well rotted manure should be placed, dug in and mixed with the soil from
the trench. No nitrogen is required.
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Peas require some sort of support for the leaf tendrils to hold on to.
Traditionally tree branches (especially Elm) were cut in winter and used to stake
the pea crop. Nowadays its more likely that plastic pea netting or sheep fencing
will be used. Whatever you choose its important that the support be placed to
the peas before the stems bend, i.e. before they have reached a height of 10 cm.
If staking is not done, peas seldom give satisfactory results. Extra early crops of
peas may be had by sowing first early varieties in pots placed in frames, early
in February and planting them out in April.
If you dont like the rather tedious job of shelling peas, consider growing either
mangetout or sugar snap peas where you can eat the pod and all. Same cultural
details, just the varieties are different.
Varieties:
Earlies: Early Onward, Meteor, Kelvedon Wonder
Maincrop: Hurst Green Shaft, Onward
Mangetout: Oregon Sugar Pod
Sugar Snap: Sugar Ann
Pests: pea and bean weevil, pea aphid, thrips, birds
Diseases: root rot, leaf and pod spot, downy mildew
Potatoes
Potatoes are a half hardy crop that hail from
South America and first reached these shores
around 1586. Being half hardy means that
frost can cause problems. It can kill off newly
emerged shoots from an early planted crop or
damage tubers (potatoes) if the harvest is left
too late.
The crop is grown from tubers; you can use your own but its probably best to
buy fresh seed annually that is certified free of disease. Seed about the size of
a hens egg is ideal. These should be planted whole, but in the event of larger
seed being used, they may be cut into two sets. The tubers can be directly
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planted into the soil but its advantageous to sprout them first as they will
emerge more quickly and mature earlier. Buy your certified seed in February or
March and place them upright in a tray placed in a light, cool, frost free place.
In a few weeks the tubers will have developed short (about 12 mm long),
sturdy, dark green sprouts.
Potatoes can be divided into 3 types in order of harvest: Early (June), Second
Early (July-August) and Maincrop (September-October).
Early potatoes are planted in March. If well sprouted potatoes planted at this
time they should be ready for use during June and July. Main crops are planted
in April to early May.
Potatoes are traditionally grown in ridges or drills. Space the drills 70 cm apart
for early and second early varieties and 75 cm for maincrop. Using a garden
line to guide you, dig out a shallow trench with a shovel, and spread
compost/manure (if you have it) and fertiliser along the base. Space the tubers
out 25 cm apart in the row for earlies and 30 cm for maincrop. Open up a
second drill parallel to the first and cover in the first trench with the soil from
the second as you go along. Continue across the plot until you are finished to
leave the ground roughly level.
The crop will require to be earthed up as it grows during the early part of the
season. As mentioned, potatoes are prone to frost damage and if the shoots are
showing and frost is forecast cover the exposed shoots with soil from between
the rows. Ridge them up again when the emerged shoots are about 20 cm high
covering them to about 10 cm. If necessary first loosen the soil between the
rows with a hoe and then use a shovel to earth up.
If you are growing on beds potatoes can be planted on the flat. Dig over the
bed, rake it level and plant the tubers using a trowel. Space them 30x30 cm in
a diamond pattern at a dept of 10-12 cm for earlies/second earlies and 15-16 cm
for main crops. When planted on the flat there is no need to earth up.
What makes for a good potato crop? A fertile soil with a full leaf canopy by the
end of May; and the development of a deep extensive root system which is
important for water uptake. And keep potato blight at bay.
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The table below gives a ranking to a number of different varieties in relation

to blight resistance in both foliage and tuber, where 1 equals lowest disease
resistance and 9 equals highest disease resistance.
Table: Blight resistance
Variety
Foliage
Tuber
Duke of York
Home Guard
Sharpes Express
British Queen
Kerrs Pink
Maris Peer
Coleen
Record
Sante
4.5
Orla
Setanta
Cara
Sarpo Mira
Rooster
Slugs: if you find you crop riddled with holes along with hollowed out cavities
the chances are that slugs are the culprit. The problem tends to be field or plot
specific its a problem in certain fields but not in others. Slug attack tends to
worse in wet years on heavy soils and varieties vary in their susceptibility.
Varieties like Kerrs Pink, Maris Piper and Rooster are vulnerable; Golden
Wonder, Nicola and Pentland Dell are among the least susceptible varieties.
Two slug species are implicated: the keeled slug and the garden slug. The
problem with trying to counter the keeled slug is that it lives mostly
underground and only comes to the surface to mate. Because of this applying
slug pellets may be of limited use. Slugs will feed on tubers from late summer
into the autumn; and essentially the longer you leave the tubers in the ground
the greater the damage. For example in a trial they discovered that Maris Piper
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lifted on August 8th suffered 10% damage, lifted on October 3rd 30% damage
and lifted in early November 45% were damaged. The following suggestions
may help:
Grow early or second early varieties as they are harvested early and hence
less susceptible to slugs.
Sprinkling a small amount of pellets along the open drill at planting time
may have some effect on reducing damage later in the season.
For main crops apply two applications of slug slug pellets in mid July and
August. Alternatively use four half-rate applications.
Consider the use of Nemaslug in early August; this is a species of eelworm

that actively seeks out slugs and kills them. But its not cheap and not
100% effective.
Avoid growing pink skinned varieties.
If you do notice slug damage towards the end of the season lift the crop
promptly as the damage will only get worse the longer the crop is in
the ground.
Do not get unduly alarmed if you notice slug damage to the potato leaves
as this may well be the grey field slug at work, a species that generally
doesnt attack the tubers.
Harvest the earlies and second earlies direct from the drill when they are big
enough and as you require them. The main crop haulm will naturally die back
in the autumn allowing the crop to be lifted in October. If you wish you can cut
the haulm off 3 weeks prior to lifting. Store the crop in a dark, frost free shed.
Varieties:
Early: Home Guard, Duke of York, Coleen, Sharpes Express
Second Early: British Queen, Orla, Maris Peer
Maincrop: Kerrs Pink, Rooster, Record, Pink Fir Apple, Cara, Setanta, Sante,
Sarpo Mira, Sarpo Axona (the Sarpo varieties may not be to everyones liking)
Pests: slugs, aphids, wireworm, eelworm
Diseases: potato blight, black leg, pink rot, soft rot, dry rot
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Radish
Radish which comes in a number of different shapes and sizes is divided into
two main types: summer and winter. Summer radishes are quick growing
maturing in 4-8 weeks and are used in salads. Winter radish is ready in 8-10
weeks and is much larger than its summer cousin; it can be eaten raw in salads
or cooked like turnip or swede.
Sow summer radish from March to August and
winter varieties from July to August. The summer
crop can be thinly sown to aim for a final spacing of
15 x 3 cm. Allow more room for the winter crop 15
x 15 cm. Summer radish can be harvested when quite
small about 2 cm in diameter. They can go woody
quite quickly so only sow in small batches and every
two weeks if succession is required.
The summer crop needs to be grown quickly so make sure to keep it well
watered in dry spells.
Varieties:
Summer types: Cherry Belle, French Breakfast, Sparkler, Rudi
Winter types: China Rose
Pests: flea beetle, slugs, cabbage root fly
Diseases: downy mildew, Rhizoctonia root rot
Rhubarb
This is an extremely useful early vegetable and a good plantation may remain
in production for many years.
Rhubarb requires a deeply worked free draining soil well manured and free of
weeds. Farmyard manure is beneficial and should be applied in the autumn
prior to planting or the ground may be fertile enough after a previously heavily
manured crop such as potatoes; fertiliser requirements can be made up by
subsequent topdressings.
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Planting material may be obtained by dividing up two to three year old stools
into a number of portions, each portion or set as it is called, should have at
least one bud and a fair portion of a root system. Plants raised from seed are
likely to be variable and are best avoided.
Plant anytime during the winter up to March if
weather and soil conditions are suitable. Sets
should be planted about 1 metre apart each way
and sufficiently deep that the crowns are level
with the surrounding soil. When growth starts a
dressing of 30g sulphate of ammonia per m2
should be given to help build up the root system.
Its best not to pull the stems the first season after
planting to allow for good establishment. When
the leaves have died down in the autumn
farmyard manure should be put around the crowns without covering them.
The rhubarb harvest normally starts in February in mild areas in the south and
in March further north in the country. During the pulling season an occasional
application of liquid manure or sulphate of ammonia will help to promote a
further flush of leaves. Take around a third to one half of the stems per stool at
any one harvest leaving the rest to allow regrowth of new shoots. When pulling
the sticks, put your hand down near the base of the stem and ease it out of the
ground. Finish pulling in August or September to allow the plant to rebuild its
reserves for the following years crop. A simple method of forcing rhubarb for
an early supply is to invert a tub over the crown at the end of January.
It may happen that some of the stools occasionally throw up flowering shoots.
These should be removed to stop the plant from expending its energy into
flower and seed production. Most commonly seen in the season following a
wet summer.
Varieties: Timperely Early, Victoria
Pests: slugs
Diseases: leaf spot (Ramularia), crown rot (Erwinia)
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Seakale
Seakale may be propagated either from seed sown in late March or early April,
or by means of root cuttings. Planting roots can also be purchased from
horticultural seedsmen. When planting out permanently remove all buds
except one, and place the rooted plants in lines 60 cm apart allowing 38 cm
between the plants in the lines.
Plants are then encouraged to grow luxuriantly until the following January
when preparations for blanching should begin. The crowns can be covered with
special earthenware pots, or alternatively, with flue liners covered on top with
tiles or slates. Fermenting manure, if placed round these coverings, will provide
gentle warmth and force the crop.
Very good blanched seakale can be obtained by heaping fine cinder ashes,
sand, sawdust or dry peat moss over the crowns. Blanching can also be done in
certain well-drained soils by covering the crowns with earth from alleyways.
When blanching is finished and the crop harvested, the materials used for
blanching should be removed and the plants encouraged to grow vigorously
and naturally through the summer, removing flower heads as they appear. In
spring a dressing of a balanced fish meal or meat-and-bone meal fertiliser plus
sulphate of potash should be given.
Spinach
This crop is grown in the same way as lettuce, but it does not transplant well.
Small successive sowings are made in rich ground, at three week intervals
throughout the spring and summer. The early sowings should be made in a
warm position, but for the summer sowings a cool site should be chosen. Early
thinning to 15 cm apart and watering with liquid manure, or dressing with
nitrogen, tend to check bolting. A sowing should be made of a prickly seeded
variety at the end of August for use in early spring.
Varieties: Fiorana F1, Medania
Pests: black bean aphid
Diseases: downy mildew
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Spinach, Perpetual
Also known as spinach beet or leaf beet this
vegetable continues to produce leaves even during
hot, dry weather. Two sowings may be made, one in
April and one in July. Sow in drills 45 cm apart and
thin the plants to 23 cm.
Seakale spinach or Swiss Chard is cultivated like
perpetual spinach. The green leaves are eaten like
spinach and the fleshy white mid-ribs are cooked and
eaten like seakale.
Swede
Swedes are a traditional winter vegetable, popular
in Ireland, thats now available all year round in the
shops. Its a hardy vegetable well able to withstand
most frosts but can bolt if sown too early.
Swedes will grow on a wide range of soils and
have a low nitrogen requirement. If conditions are
too rich they will split and develop soft rots. So its
best not to apply any compost or manure prior to
sowing the crop and watch the nitrogen. They are
also tolerant of low pH (see Table 1 in the Appendix).
Magres which was introduced in 1980 is the standard commercial swede variety.
It is a high dry matter variety and as such hardy in most winters but also renders
it hard to chop in the kitchen when it reaches maturity. Marion has good
resistance against clubroot and powdery mildew. Helenor which has increased
in popularity in recent years has a dark purple colour with a sweet taste. Gowrie
is a Scottish variety that exhibits vigour, good resistance to downy mildew and
is suitable as an early variety. Hybrid varieties are a new development in swedes
and the best of them is Tweed which is a vigorous variety well suited to less
fertile soils and produces uniform globe shaped roots.
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The crop is normally direct drilled but early crops can be sown under protection
in modules and planted out. The direct drilled crop is sown from April to the
end of June with the main crop sown in May. In comparison to turnips swedes
are quite a slow crop to develop but will stay fit for harvest for many months.
It takes about 15 weeks for the first ones to come fit. For an early crop (mid
June to early July) sow in modules mid February, transplant out in March to
early April using a wide spacing and cover with fleece. This early crop may bolt
but you will still be able to harvest a crop.
Crop density usually varies from 10-16 plants per m2 with around 13 per m2
fairly typical for a commercial crop that requires a 0.8-1 kg head weight. You
can experiment with different spacings depending on your requirements but
try 40x20 cm that equals 12.5 per m2. For early or late crops increase the spacing
a bit to 40x25 or 40x30 cm.
Swedes are prone to a disorder called Brown Heart
which is caused by a deficiency of boron, that can be
particularly prevalent on high pH soils. If you come
across the problem apply 2-4 g per 10 m2 of Borax at
the 4 leaf stage to prevent its occurrence in
subsequent seasons. Commercial growers spray
routinely for this common problem.
There are two pests that can cause trouble. If you notice pin-prick holes in the
leaves when the plant is small, particularly during a spell of fine weather, its
probably flea beetle. If you spot white maggots feeding on the roots its more
than likely to be those of cabbage root fly. In both cases the best way to avoid
them is to use crop covers, either fleece or bionet. If you delay your sowing to
late May youll avoid the first generation of cabbage root fly, which is always
significantly worse than the second generation which occurs from July to
September. Swedes are also prone to downy mildew but is normally not a
problem as the crop will grow out of it. In warm dry summers powdery mildew
can make an appearance and if desired can be controlled with sulphur sprays.
Varieties: Brora, Helenor, Marion, Ruby, Magres, Gowrie, Tweed F1
Pests: cabbage root fly, flea beetle, aphid
Diseases: powdery mildew, downy mildew, crater spot, dry rot (Phoma), club root
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Sweetcorn
Sweetcorn developed thousands of years ago
as a natural variant of maize which is a native of
central America, probably Mexico. It was
brought to Europe by Columbus and
subsequently spread worldwide to become one
of the most important food crops for mankind.
Sweetcorn differs only in a single gene from maize which slows down the conversion of
sugar to starch. This produces kernels with a high sugar content and pleasant texture in
contrast to the starchy grains of maize. It now only exists in cultivation and thus could be
described as being a man-made crop.
This vegetable was transformed for the commercial grower by the development of
supersweet varieties in the mid 1980's. These varieties possess sh2 genes which
causes them to convert much less of their sugar to starch to produce kernels about
30% sweeter than the standard ones (known as normal sugar), but more importantly
hold their sweetness for longer. The old varieties, once ripened, quickly converted their
sugars into starch and had to be used immediately. Other types you may come across
in catalogues are 'sugar enhanced' varieties which have a sweetness in-between
normal and supersweet and 'extra-tender sweet' varieties which are a sweeter and
less chewy version of the supersweets.
Sweetcorn is one of the half-hardy vegetables and is better suited to the warmer
eastern and southern parts of the country. But the development of new varieties has
rendered the crop less susceptible to the vagaries of an Irish summer. That said it will
always do better in a warm summer and select a warm sheltered site if possible.
Most of the varieties available are hybrids. The supersweet and extra-tender varieties
can be grown together but must be separated from the normal sugar varieties plus the
whites and multicoloured types. All varieties must be isolated from forage maize by at
least 75m as the starchy character of maize is dominant to the sweet character of
sweetcorn. If you're growing sweetcorn in one of the colder areas of the country you'd
be advised to stick with using just the early varieties such as Earlibird or Northern Xtra
Sweet.
Maize is grown commercially in Ireland for silage production and a lot of the crop is
direct drilled through a strip of biodegradable clear plastic. The plastic increases the
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soil temperature by about 2-4C which generates better growth especially for the
earlier sown crops. Maize requires a temperature of 10-12C to germinate and
doesn't thrive at air temperatures less than 10C.
Unusually for a vegetable crop it's a member of the grass family (Poaceae) and as
such is wind pollinated. For this reason sweetcorn is sown or planted in blocks to
allow the pollen produced by the male tassels produced at the top of the plant to
fertilise the female flowers known as cobs.
Sweetcorn is not a crop that takes to transplanting well but the first sowing can take
place indoors to be planted out carefully later. Sow 2.5 cm deep in large modules or
pots under glass in mid April to early May and plant out when the plants are 10 cm tall.
Plant in a block formation at a spacing of 45x45 cm or 45x40 cm for a higher density
plant population for sweetcorn can vary from 4.8-6 plants per m2. Alternatively direct
drill the crop outdoors at similar spacings, in May to the first week in June. In warmer
parts of the country and if drilled under clear plastic an early crop could be sown in
April. The earlier drillings can with advantage be covered with fleece until well
established, particularly if the weather is on the cool side. If not covered by fleece or
plastic crops probably shouldn't be drilled until mid May.
Sweetcorn is quite a nitrogen demanding crop. Up to 70 g/m2 of sulphate of ammonia
can be used split half at sowing or planting and the other half a month later.
The crop is harvested from August through to October. The silks which hang from the
developing cobs turn brown shortly after pollination and to a dry dark brown when the
cob is close to harvest about 30 days later. The final test of ripeness is to push a
fingernail into one of the grains if the liquid runs clear it's unripe; if it's milky it's ready
to harvest. You will normally harvest 2 cobs per plant. The top cob matures first
followed by the one further down the plant. The supersweet varieties will last
satisfactorily in a fridge up to a week.
Varieties
Normal sugar: Sundance F1
Supersweet: Northern Xtra Sweet F1, Earlibird F1, Mainstay F1, Seville F1
Extra-tender: Lark F1, Lapwing F1, Wagtail F1
Pests: aphids
Diseases: rust
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Tomato
Tomatoes are a half hardy vegetable that give the best results when grown in a
glasshouse or polythene tunnel. That said, if you have a sheltered warm spot in your
garden or allotment, you can try growing them outdoors. There are two types
bush (or determinate) and cordon (or indeterminate). The bush varieties require little
staking but dont yield as well as the more traditional cordon types which require
both staking and side shooting. Bush types are possibly more suited for containers
or pots and would recommend the cordon type for the vegetable garden.
Outdoor tomatoes are raised under protection and planted
out in June when all frosts are gone. You can propagate your
own plants or more conveniently buy them in at planting
time. Sow 1-2 seeds in a 8 cm pot sometime in April, about 8
weeks before your chosen planting date sometime in June.
You require a plant density of about 4 per m2 so space them
at 50x50 cm and put a 1.2 m stake beside each plant. As the
plants grow they will have to be tied into the stake and the
little side shoots that develop in the leaf axils need to
be removed by snapping them off when they are about
3 cm long.
Tomatoes are heavy feeders so they would be a good crop to receive manure or
compost and when watering apply a liquid feed as standard. Pinch out the
growing point in August two leaves above the last flower truss this is to get
the plant to put all its energy into developing and ripening the fruit before the
first frosts of autumn.
Varieties: Gardeners Delight (cherry), Alicante (round), Ailsa Craig (round),
Ferline (beefsteak)
Pests: caterpillar
Diseases: potato blight
Disorder: blossom end rot (calcium deficiency)
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Turnip
Turnips are a quick growing crop maturing in as little as
6 weeks from sowing. They come in a variety of shapes
flat, round or long and in a variety of colours
purple, green or white. Its a versatile crop that can be
harvested when small and eaten raw or left to grow in
size and cooked; the tops can also be harvested like
spring greens from a late summer sowing.
A small sowing should be made about every three to four weeks from March
to August in drills 30 cm apart and 2 cm deep. Sow thinly and gradually thin out
to 15 cm apart. Start harvesting when they are golf ball sized for salads or grow
on to tennis ball size for cooking.
The main problems will stem from attack by cabbage root fly, flea beetle and
slugs. Your best bet is to cover the crop with fleece for the first two and a small
amount of pellets to keep slugs at bay. As with any quick maturing crop water
the crop during dry spells.
Varieties: Oasis, Purple Top Milan, Goldenball, Green Globe, Sweetbell F1
Pests: Flea beetle, cabbage root fly, slugs
Diseases: downy mildew
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Herbs
There is a very wide selection of these useful flavouring plants and only
the enthusiast grows all of them. Room should be made in every garden for
few of the more commonly used kinds. Choose a warm, sunny site for your
herb garden.
Thyme: Sow seed in April and thin or transplant to 15 cm apart. Will last for
several years.
Mint: Plant in October or March in a cool, rich soil. Cut down the tops in autumn
and cover with 5 cm of manure or compost.
Sage: Grow from seeds in April or cuttings in July or August. Plant 40 cm apart
in a dry position. Each spring prune back the branches to ensure a supply of
fresh growth.
Chives: Clumps may be bought from seedsmen and planted in early spring.
Leaves are cut during summer as required.
Coriander: This annual plant is grown for both its leaves and seeds. Direct drill
from March to July for harvesting from May to October. For May harvest sow
under protection or in a garden frame. Sow every 3 weeks for succession.
This crop is prone to bolting so keep well watered to prevent checks to growth.
This plant hails from the Mediterranean and doesnt thrive outdoors in cool,
wet summers.
Parsley: There are two types of this popular herb: curly and flat leaved. The flat
version is the more flavoursome of the two. The seed should be sown in March/
April, in lines 45 cm apart and thinned to 5 cm apart. A sowing may also be
made in July for winter and spring use. Parsley can also be raised in modules
and planted out. Its a biennial plant and several cuttings can be taken from a
single sowing before the plants go to seed.
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Tender and out of season vegetables

Dutch lights, polythene tunnels or polythene mulch will be found of great
assistance in raising out of season and frost tender vegetables.
Dutch light frames Dutch lights consist of a single frame of 600g glass measuring
142 x 73 cm slipped into grooves on the long sides of a light wooden frame. These
lights can be used to cover a frame with 60 cm back wall and 45 cm front wall. The
frame may be heated by electric cables or crops may be grown without heat.
Polythene Tunnels These are of two main types:(1) Low tunnels which have replaced cloches. A roll of 150 gauge polythene is
supported by wire hoops and secured by twine. These tunnels are very
useful for low growing crops or for providing shelter in the early stages of
a crops development.
(2) Walk in tunnels these are a low cost alternative to glasshouses. Polythene
(600 gauge) is drawn tight over galvanised metal tubing forming a
semicircular shape. These tunnels can be used for raising plants or growing
more tender or out of season vegetables including tomatoes, cucumbers,
melons, aubergines and sweet peppers.
Black Polythene mulches If black polythene is laid on the ground and secured
at the edges, many tender crops grow better than if planted into the open
ground. The best system of culture is to raise the plants indoors or in a heated
frame or glasshouse and to plant through holes in the polythene mulch when
all danger of frost is gone. Tomatoes, gherkins, marrows and sweet corn benefit
especially from these mulches.
Cropping Programmes Under any of the above systems careful planning and
management are needed if the protected area is to be utilised to full
advantage. Suitable varieties should be used and dates of sowing and
transplanting carefully studied. Many variations in cropping programmes can
be employed. Early sowings of carrots in January will mature in May and can be
followed by tomatoes, cucumbers, peppers or aubergines which in turn can be
followed by lettuce. Alternatively lettuce can be succeeded by celery planted in
late July for harvesting in early December.
87
Vegetable production in Ireland
Area of commercial vegetables grown: 4590 ha.

Home grown produce supplies 60% of the market.
Top 5 vegetable growing counties: Dublin, Meath, Cork, Wexford, Louth.
Top 5 vegetables grown in Ireland: Cabbage, carrots, broccoli,
swede, cauliflower.
Top 5 vegetables eaten in Ireland: Tomato, carrots, mushrooms,
peppers, onions.
Source: Bord Bia National Field Vegetable Census 2009
88
APPENDIX
Table 1: Guide to pH values below which crop growth is affected
Crop
Soil pH
Crop
Soil pH
Asparagus
5.9
Mint
6.6
Bean
6.0
Mustard
5.4
Beetroot
5.9
Onions
5.7
Broccoli
6.0
Parsley
5.2
Brussels sprouts
5.7
Peas
5.9
Cabbage
5.4
Potato
5.0
Carrot
5.7
Rhubarb
5.4
Cauliflower
5.6
Spinach
5.8
Celery
6.3
Sweetcorn
5.5
Chicory
5.2
Swede
5.4
Leeks
5.8
Tomato, outdoor
5.2
Lettuce
6.1
Turnip
5.4
The above picture shows a swede plant growing in a mineral soil at a pH of

4.9. Notice the cupping of the leaves with a pale outer rim to the leaves that
are characteristic symptoms of manganese toxicity.
89
Table 2: Guide to dept of sowing

12-20 mm
20-25 mm
25-38 mm
38-50 mm
Beetroot
Carrot
Leek
Lettuce
Onion
Parsley
Parsnip
Spinach
Broccoli
B. sprouts
Cabbage
Cauliflower
Cucumber
Marrow
Radish
Swede
Tomato
Turnip
Pea
Sweet corn
Broad bean
French bean
Runner bean
Table 3: Soil sample laboratories

Any local Teagasc office will accept samples www.teagasc.ie
Southern Scientific Services
Dunrine, Killarney, Co Kerry
Tel: 064 - 6633 922
F.B.A. Laboratories Ltd
Carrageen Industrial Estate, Cappoquin, Co Waterford
Tel: 058 - 52861
EURO Environmental Services
Unit 35, Boyne Business Park, Drogheda, Co Louth
Tel: 041 - 9845 440
IAS Laboratories
Unit 4, Bagenalstown Business Park, Bagenalstown, Co Carlow
Tel: 059 - 9721 022
Dairygold Feed Laboratory
Lombardstown, Mallow, Co Cork
Tel: 022 - 47275
90
Table 4: Seed companies

Suttons Seeds
Woodview Road
Paignton
Devon
TQ4 7NG
Thompson & Morgan

Poplar Lane
Ipswich
IP8 3BU
Unwins
Alconbury Hill
Huntingdon
Cambridgeshire
PE28 4HY
Mr Fothergills
Kentford
Suffolk
CB8 7QB
Kings Seeds
Monks Farm
Kelvedon
Colchester
Essex, CO5 9PG
Moles Seeds
Turkey Cock Lane
Stanway
Colchester
Essex, CO3 8PD
The Organic Gardening Catalogue

Riverdene Business Park
Molesey Road, Hersham
Surrey, KT12 4RG
Dobies of Devon
Long Road
Paignton
Devon, TQ4 7SX
Johnsons Seeds
Kentford
Suffolk
CB8 7QB
Tamar Organics
Cartha Martha Farm
Rezare, Launceston
Cornwall, PL15 9NX
M.G. Seed Company (Moles Seeds)

Sutherland
Ratoath
Co Meath
087 - 262 3133
Colum ORegan
Horizon Farm
Kinsale
Co Cork
Tel: 087 - 763 7574
91
Table 5: Latin names of vegetables

ALLIACEAE
Allium cepa
Var ascalonicum
Var cepa
Allium fistulosum
Allium porrum
Allium sativum
Allium schoenoprasum
APIACEAE
Apium graveolens
Coriandrum sativum
Daucus carota
Foeniculum vulgare
Pastinaceae sativa
Petroselinum crispum
Formerly Umbelliferae
Var dulce
Var rapaceum
Var azoricum
ASTERACEAE
Cichorium endivia
Cichorium intybus
Cynara scolymus
Helianthus tuberosus
Lactuca sativa
Formerly Compositae
BRASSICACEAE
Armoracia rusticana
Brassica napus
Formerly Cruciferae
Brassica oleraceae
92
Shallot
Onion, salad onion
Japanese bunching onion
Leek
Garlic
Chives
Celery
Celeriac
Coriander
Carrot
Florence fennel
Parsnip
Parsley
Endive
Chicory/Radicchio
Globe Artichoke
Jerusalem Artichoke
Lettuce
Var napobrassica
Var napus
Var acephala
Var botrytis
Var capitata
Var gemmifera
Var gongylodes
Var italica
Horseradish
Swede
Oilseed rape
Kale
Cauliflower
Cabbage
Brussels sprouts
Kohlrabi
Broccoli/calabrese
Table 5: Latin names of vegetables continued

Brassica rapa
Var chinensis
Var nipposinica
Var pekinensis
Var rapa
Pak choi
Mizuna
Chinese cabbage
Turnip
Rocket
Water cress
Radish
Garden cress
Subspecies cicla
Subspecies vulgaris
Spinacia oleraceae
Leaf beet, Swiss chard

Beetroot
Spinach
CUCURBITACEAE
Cucumis melo
Cucumis sativus
Cucurbita pepo
Melon
Cucumber, Gherkin
Marrow, Courgette
Eruca sativa
Nasturtium officinale
Raphanus sativus
Rorippa x sterilis
CHENOPIACEAE
Beta vulgaris
FABACEAE
Phaseolus coccineus
Phaseolus vulgaris
Pisum sativum
Vicia faba
Formerly Leguminosae
Var major
Scarlet runner bean

French bean
Pea
Broad bean
POACEAE
Zea mays
Var saccarata
Sweet corn
POLYGONACEAE
Rheum x cultorum
Rhubarb
SOLANACEAE
Capsicum annum
Capsicum frutescens
Lycopersicon esculentum
Solanum melongena
Solanum tuberosum
Sweet pepper
Chilli pepper
Tomato
Aubergine
Potato
93
Vegetable production guide

Crop
Season Sow
Bean broad
Early
Main
Plant
Spacing Harvest
cm
Oct Nov
Feb May
23x23
60 rows
Early June on
June Sep
Bean French
Mid May
June
45x8
July
October
Bean runner
Mid May
June
60x20
Aug Sep
Beetroot
Apr June
25x4
July March
15x7
15x5
15x5
July Aug
Sep March
Carrots
Early
Main
Late
Feb March
April May
June
Celery
Early
Main
Late
March
April
May
May
June
July
30x30
30x30
30x30
Aug Sep
Sep Oct
Nov Dec
Courgettes
Main
Late
April May
June
May June
June July
80x80
90x75
July Sep
Sep Oct
Garlic
Early
Main
Oct Nov
Feb Mar
20x20
20x20
May June
July Aug
Leeks
Early
Main
Late
April
May June
June July
30x20
30x15
30x20
Aug Sep
Oct Feb
March Apr
Onion
Shallot
Sets
Feb Mar
Feb Apr
Early Oct
30x15
25x10
25x10
25x7
July Aug
August
July
Aug Sep
Seed
94
Jan Feb
March
April
Feb-March
Vegetable production guide continued

Crop
Season
Sow
Parsnips
Early
Main
Parsley
Spacing
cm
Harvest
March
April May
30x15
July on
Aug March
Early
Main
September
March July
45x5
May
June on
Peas
Early
Main
Late
March
April May
June
90 rows
June July
July Aug
Sep Oct
Potatoes
Early
Main
70x25
75x30
June July
Aug Oct
15x3
May Oct
1x1 m
March Aug
25 cm
rows
April May
Main
August (last 2 Sow 20-30

seeds per
weeks)
30 cm
Feb June
Spinach
Early
Main
September
Mid Mar - July
30x15
30x15
March April
June Oct
Swede
Early
Main
Late
March (fleece)
April May
June
40x23
40x20
July
Aug March
October on
Early
Main
Late
April (glass)
May
Early June
45x40
45x45
45x45
August
September
Sep Oct
30x15
June Nov
Radish
March
April
March Aug
Rhubarb
Scallions
Sweetcorn
Turnip
Plant
Winter
time
Early
April Aug
May
June Oct
95
Vegetable aphids (greenfly)

Crop
Species
Occurrence
Beans
Broad/French/Runner
Black bean aphid

Aphis fabae
Common
Brassicas
Mealy cabbage aphid

Brevicoryne brassicae
Common
Peach-potato aphid
Myzus persicae
Frequent
Willow-carrot aphid
Cavariella aegopodii
Common
Carrot root aphid

Pemphigus phenax
Uncommon
Potato aphid
Macrosiphum euphorbiae
Common
Peach-potato aphid
Myzus persicae
Common
Lettuce aphid
Nasonovia ribisnigri
Frequent
Lettuce root aphid

Pemphigus bursarius
Uncommon
Peas
Pea aphid
Acyrthosiphon pisum
Common
Potato
Potato aphid
Macrosiphum euphorbiae
Common
Peach-potato aphid
Myzus persicae
Common
Carrots/Celery
Lettuce
Glasshouse-potato aphid
Aulacorthum solani
Spinach
96
Black bean aphid

Aphis fabae
Common
History of the Swede

The swede is a comparatively recent vegetable whose origin is uncertain but
possibly originated in Finland. It arose from a cross between Brassica rapa
(turnip) and B. oleraceae (possibly kohlrabi) and was first recorded by a Swiss
botanist Caspar Bauhin in 1620.
The swede spread to other countries including
Holland and Sweden where it became popular as
stock feed and as a winter vegetable for humans.
There is a record for its introduction into
Scotland in 1781-1782 and a mention in the
Gardeners Chronicle of its introduction into
England in 1790. It presumably arrived in Ireland
sometime after.
The name swede derives from the time that Sweden began to export their crop
to Britain its a shortened version of Swedish turnip, turnip being very similar
in looks to swede. Sweden also exported the crop to North America from
whence came the American name for swede, rutabaga, which comes from the
old Swedish word rotabagge, meaning "root ram".
Whats the difference between a turnip and a swede?
Both are formed from the hypocotyl (that bit of the stem
just below the seed leaves) swelling up into the familiar
root, but in the swede the top and bottom of the bulb
are derived more from stem and root tissue, respectively,
than is turnip. This leads to leaf scars giving a swollen neck
around the top of the swede and the presence of
adventitious roots on the bottom of the bulb.
97
A Guide to
Vegetable Growing
Teagasc, Oak Park, Carlow

info@teagasc.ie
www.teagasc.ie
June 2013

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A Guide to

Cultivation of the Soil

Pests and Diseases

Plant Raising and Direct Drilling

Tender and Out-of-Season Vegetables