THE UNIVERSITY OF ARIZONA

COLLEGE OF AGRICULTURE AND LIFE SCIENCES

TUCSON, ARIZONA 85721
ROBERT E. CALL
Former Area Horticulture Agent
CADO DAILY
Coordinator, Water Resources
CONTACT:
CADO DAILY
cdaily@cals.arizona.edu
This information has been reviewed by University faculty.
cals.arizona.edu/pubs/water/az1298.pdf
Originally published: 2006
Other titles from Arizona Cooperative Extension can be found
at:
cals.arizona.edu/pubs
Signs of under- and over-watering
Under-watering
Soil is dry.
Older leaves turn yellow or brown and may even
drop off.
Leaves are wilted and/or curled.
Over-watering
Soil is constantly damp.
Young leaves become light green or yellow.
Young shoots are wilted.
Leaves are green yet brittle.
Algae and mushrooms are growing.
Tips for efficient watering
Control weeds. Do not lay plastic over the soil. Use
mulch or porous landscaping fabric instead to
allow water and air to circulate in the root zone.
Avoid sprinkling tree and shrub leaves with water.
Salts in the water can damage the foliage.
If trees or shrubs are planted in turf, water them
separately at the drip line.
If you water by hand, install a faucet timer and
use a soaker hose or in-line driphose.
Once or twice a year water three times longer than
normal to help leach salts out of the root zone.
Prevent runoff by retaining water in a donut basin
around the plants drip line or water at a slower rate.
Move the 1 foot wide donut ring outward as the
plants grow.
Watering in the early morning will be most efficient
because of less wind and heat.
Use rain and stormwater when possible to reduce
tap water its better for your plants!
Watering Trees
and Shrubs
Simple Techniques for Efficient
Landscape Watering
For more information
Visit cals.arizona.edu/pubs to view additional
publications on:
Low Water Use, Low-maintenance Landscaping
Improving Irrigation Efficiency
Plant Selection
Water Harvesting
Erosion Control
Composting
RainScapes
Water Conservation
Other topics
More information on University of Arizona Cooperative
Extension programs and activities can be found at
extension.arizona.edu
Any products, services, or organizations that are mentioned, shown,
or indirectly implied in this publication do not imply endorsement by
The University of Arizona.
AZ1298
Issued in furtherance of Cooperative Extension work, acts of May
8 and June 30, 1914, in cooperation with the U.S. Department of
Agriculture, Jeffrey C. Silvertooth, Associate Dean & Director, Economic
Development & Extension, College of Agriculture and Life Sciences, The
University of Arizona.
The University of Arizona is an equal opportunity, affrmative action
institution. The University does not discriminate on the basis of race,
color, religion, sex, national origin, age, disability, veteran status, or
sexual orientation in its programs and activities.
Weather
Plants use 3 to 5 times as much water during the hot, dry,
windy seasons as they do during the winter. Adjust your
watering schedule with the season and when there are
significant changes in the weather.
Plant Maturity and Type
To prevent wilting, young plants should be watered more
often than older plants. After they become established, in
one or two-years, allow a slight drought between waterings.
The plants will adapt to the stress and become more
drought tolerant.
Soil Type
If your soil is shallow, compacted or sandy, irrigate more
often but for less time. Clay soil can hold water more tightly
and absorbs water slowly. Water clay soils slowly and less
often. A sandy loam soil penetrates evenly.
Mulch
Keeping water from evaporating is key to keeping water
in the ground for plant use. A 3 to 4 layer of an organic
(for example shredded bark) or inorganic (rock) mulch
on top of a plants root zone will significantly reduce the
frequency of watering. Keep mulch away from base of
plant to avoid rot.
SummerGenerally you should water mature trees and shrubs
no more than once a week. Water arid adapted plants less
often, if at all.
WinterIf there has not been any precipitation for four to six
weeks, water deciduous and evergreen trees and shrubs.
COLLEGE OF AGRICULTURE
AND LIFE SCIENCES
COLLEGE OF AGRICULTURE
AND LIFE SCIENCES
COOPERATIVE EXTENSION
February 2014
Lawn and Garden 6 - 12
Shrubs 12 - 24
Trees 18 - 36
How much should I water?
Be sure to water the root zone to the indicated root
depth every time you water (see table below). How will
you know this? Push a soil probe, a smooth rod (

to
3
/8


diameter), into the ground soon after you irrigate. The soil
probe should easily slide through the wet soil and become
difficult to push when reaching dry soil. Watering deeper
than the root zone only means you are wasting water.
Typical Root Zone Depth for Mature Plants
How often should I water?
Water consumption rates vary greatly among plant
species. High water use plants like cottonwood and
willow trees that grow naturally along waterways need
much more water than established arid region plants. A
good rule of thumb is to water when your soil probe wont
penetrate the ground more than 3 to 4.
Root depth
Root depth has a major impact on how often plants
need water. Deeper rooted plants need less frequent
watering. Encourage a deep, drought-resistant root zone
by watering deeply, infrequently and at the drip line where
many fine roots can absorb more water.
How long should I water?
The amount of time needed to sufficiently water your
plants depends on how much water your irrigation system
delivers, root zone depth, weather, and type of soil. Monitor
how quickly the water soaks into the soil using a soil probe.
Remember, you want water to reach the full depth of
your plants root zone, but no deeper. Once you have
determined how long it takes to fill the root zone, try to
irrigate the same amount of time when watering.
Seasonal plant water use
Plants dont waste waterpeople do!
How much water do trees and shrubs really need? How
often should they be watered? Where should it be applied?
Most people over water plants. Over-watering can
damage or even kill plants, leaving you with high water bills.
Learning to water efficiently and effectively is easy. This
brochure provides some basic guidelines on how to
properly water trees and shrubs.
Where should I water?
The soil surrounding the plants roots, called the root
zone, serves as a storage tank from which the plant draws
moisture and nutrients. Most trees and shrubs shed rain
water to the drip line (the area below the edge of the
plants canopy), much like an umbrella. The most active
water absorption area is at the drip line and beyond, not
close to the trunk. This is where you should water. Most
of the roots spread 1

to 4 times as wide as the plants
canopy.
How should I water?
Drip SystemsMost drip systems do not have enough well
placed and spaced emitters. Add emitters and move out
to the drip line as the plants grow.
BubblersBe sure the basins are level and are a 1 foot
wide donut just inside and outside the edge of the
canopy. Do not water near the trunk.
Soaker HosesA perforated hose is a good device for
watering, but can plug and emit water in a random
pattern.
In-Line DripPoly tubing with drip emitters inside.
SprinklersCover a large area but can be inefficient
because of wind and evaporation. Not recommended
for watering trees and shrubs.
I f trees are i n a l awn, water the trees
separately from the grass. Deep watering
promotes deep rooting of trees and shrubs.
If not, tree roots may grow on the soil surface.
Suggested Watering Depth for
Different Types of Plants