How to Grow and Care for Coleus Plants

Mostly grown as annuals, coleus are low-maintenance plants with attractive foliage. What makes coleus so popular is its versatility: the plants are easy to grow, stay vibrant in both sun and shade, and tolerate almost any soil type. New colors and patterns of coleus are introduced regularly including dwarf varieties, trailing types, and big-leaf, upright plants that grow to 3 1/2 feet tall.

The blue or white flowers on the mature plant are secondary and many gardeners remove them to encourage more brilliantly colored leaves. Planted in spring, coleus provides season-long interest, dying back with the first frost. Unlike coleus in the garden, indoor coleus lasts for several seasons.

Coleus is toxic to pets.

Coleus Care

As there are coleus varieties for different levels of sun exposure, make sure to choose a variety that is suitable for the planting location. Here are the main care requirements for growing coleus:

• Plant in rich, loose, well-worked garden soil or quality container plant mix.
• Wait to plant outdoors until the temperature reaches 60°F.
  
• Keep the soil consistently moist and water when the top inch of soil feels dry.
• Keep mulch from contacting stems and avoid cedar mulch
• Protect outdoor plants when temperatures dip below 50°F.

Light

The amount of sun or shade coleus needs depends on the variety. Newer cultivars, like the Wizard series, are more tolerant of sun than older types. Most varieties are suited to shady spots and do well with morning sun and afternoon shade.

Coleus grown indoors usually get sufficient light during the summer but may need to be supplemented with a grow light in winter to prevent the plant from getting leggy.

Soil

Coleus prefers consistently moist, rich, well-draining soil with a pH between 6.0 and 7.0. Before planting, amend the soil with compost or another organic material. For potted plants, use a good-quality potting mix.

Water

The soil in which coleus grows best should be consistently moist but not soggy. Long dry spells slow the plants’ growth, and leaves start to brown around the edges. Let the soil dry out between watering and water when the top inch of the soil feels dry to the touch. Containers need water more often, up to twice a day during hot weather.

Mulching helps retain moisture (avoid cedar mulch, which may render the soil too acidic for coleus).

Temperature and Humidity

Coleus thrives in hot, humid conditions. Light frost kills large-leaved types. Wait until the temperature reaches 70°F before moving potted plants outdoors in spring. In the late summer and fall, move potted plants indoors or use an insulating cover when temperatures dip into the 50s.

Keep indoor plants away from air conditioner vents and drafts. If the air in your home is dry, use a humidifier to keep it at a minimum of 50% (between 50% and 70% humidity is ideal for coleus).

Fertilizer

Coleus is sensitive to fertilizer, which, when overused, leeches color from the leaves. When grown in rich soil, feeding isn't necessary. Amend the bed beforehand or add a balanced slow-release fertilizer at planting time. Feed container-grown plants once a month with a water-soluble fertilizer.

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Types of Coleus

There are hundreds of coleus plant varieties available in different colors, leaf textures, and patterns. New cultivars are developed each year, and garden centers tend to focus on a select popular few. Shop several different places to find more unique varieties. Some types to look for include:

• Wizard series: Small 12- to 14-inch plants in standard color mixes easy to grow from seeds.
• Kong series: These varieties feature 6-inch leaves on 2-foot tall plants sensitive to direct sunlight.
• 'Black Dragon': A unique variety with deep burgundy leaves and ruffled edges that grow to 18 inches tall.
• Premium Sun series: Cultivars bred to tolerate full sun.
• Fairway series: Dwarf cultivars growing 6 to 10 inches tall in a variety of leaf patterns and colors.

Pruning

For full, bushy plants, pinch out growing tips when plants are about 6 inches tall. Using pruning shears, pinch just under the flower buds to promote leafy growth instead of flowers and seeds.

Plants that are not pruned tend to get leggy and lose their shape.

Propagating Coleus

Coleus plants are best propagated by taking stem cuttings.

1. Take a cutting: Using sharp, sterile pruning shears to cut a 4- to 6-inch long stem. Make the cut below a leaf node.
2. Strip off the leaves: Remove leaves from the lower half of the cutting leaving one or two at the top. Cut large leaves in half to facilitate rooting.
3. Plant the cutting: Dip the cut end of the stem in rooting hormone and insert the cutting in a pot filled with moistened potting mix.
4. Cover the cutting: Use a clear plastic dome or a bag to cover the cutting, making sure the plastic doesn't touch the cutting.
5. Place it in a suitable spot: Put the covered cutting in a bright, warm location with a temperature of 70°F.
6. Water the cutting: Keep the soil consistently moist. Roots develop in two to three weeks.
7. Remove the cover: Take off the plastic cover and continue growing the new plant in a bright, warm location.

How to Grow Coleus From Seed

Modern coleus varieties sold in nurseries and garden centers are hybrids grown from cuttings and the seeds of these plants won't be true to the parent. But seed companies sell coleus varieties that are worth growing from seed, which is easy. It takes about 21 days for germination and then three or four weeks of warm weather for fully grown plants. For planting outdoors, start seeds indoors about eight to 10 weeks before your last frost date.

1. Sprinkle the tiny seeds over a tray filled with potting mix and press them lightly into the soil. Do not cover.
2. Add a clear plastic dome or cover and set the tray in a bright, warm spot with temperatures between 70 and 75°. Germination occurs in three weeks.
3. Remove plastic and continue to keep the soil consistently moist.
4. When two sets of true leaves appear and seedlings are sturdy enough to handle, transplant them into small pots until outdoor planting time. Make sure to harden off the seedlings before planting in the garden.

Potting and Repotting Coleus

Coleus grow rapidly so start with a pot large enough to accommodate the mature plant. For tall, upright varieties choose a heavy 12-inch pot such as terra-cotta to help anchor heavy top growth. Choose containers with large drainage holes.

Common Pests & Plant Diseases

Coleus are susceptible to mealybugs, aphids, spider mites, whiteflies, and slugs. A few insects on a plant can often be controlled with a strong spray from a garden hose. If the infestation is severe, you might have to resort to an insecticide such as insecticidal soap. Mulch discourages slugs. Groundhogs and young rabbits will nibble your coleus leaving them with an unsightly ragged appearance.

Coleus is not usually bothered by disease. In cool, damp weather, fungal diseases such as powdery mildew may appear. Good drainage prevents root and stem rots.

Common Problems With Coleus

Coleus is a reliable, showy foliage plant with few problems. Fungal infections usually start during periods of cool, humid weather. Here are a few common issues:

Yellow Leaves

Chlorosis causes leaves to turn yellow, tracing back to a number of problems usually due to errors in care. Overwatered plants develop yellow, mushy leaves. Underwatering causes foliage to fade, yellow, and turn brown and crispy.

Too much fertilizer interferes with chlorophyll production. Use a balanced formula in the garden only in cases of poor soil and a water-soluble product for container plants. Choose the correct pot size starting out. Rootbound coleus also develops yellow leaves.

Leaf Spores

Downy mildew is a fungal infection that flourishes in cool, humid conditions causing stunted growth and loss of foliage. Fuzzy gray and purple spores appear on the undersides of leaves affecting lower leaves first. Avoid overcrowding plants for better air circulation and water in the morning. Remove infected leaves.

Wilting

Big leaf cultivars may wilt following transplant into the garden or if they receive too much direct sun. Make sure the variety you choose is suited to sun exposure for the intended garden spot. Water new transplants in well and keep soil moist but avoid overwatering.