Coleus Plants: Care & Growing Guide

Coleus are foliage plants in a wide selection of colors and patterns for the annual garden. They are easy to grow, stay vibrant in both sun and shade, and are tolerant of soil type. New colors and patterns are introduced regularly including dwarf varieties, trailing types and big-leaf, upright plants that grow to 3 1/2 feet tall.

At maturity, coleus produces tiny blue or white flowers on spikes but these are often pinched out to encourage more brilliantly colored leaves. Planted in spring, coleus provide season-long interest, dying back with the first frost. It's most often set out in the garden but can be grown indoors for several seasons. Coleus is toxic to dogs, cats and horses.

Coleus Care

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

Light

How much sun to give your coleus depends on the variety you choose. Newer cultivars, like the Wizard series, are more tolerant of light than older types. Most varieties are suited to shady spots and do well with morning sun and afternoon shade.

Plants grown indoors usually get sufficient light during the growing season but may need to be supplemented with a grow light in winter.

Soil

Coleus prefers consistently moist, rich, well-draining soil. Before planting, amend the soil with compost or another organic material. For potted plants, use a good-quality potting mix. Choose a container with drainage holes.

Water

Coleus plants grow best in soil that is 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.

Mulch helps retain moisture, but don't use cedar mulch, which is toxic to coleus. Containers need water more often, up to twice a day during hot weather.

Temperature and Humidity

Coleus thrives in hot, humid conditions. In temperate climates, light frost can kill large-leaved types. 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. In dry climates, the plants benefit from extra humidity. Wait until the temperature reaches 70°F before moving potted plants outdoors in spring.

Fertilizer

Coleus is sensitive to fertilizer which can leech color from the leaves if overused. 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. Pinch just under the flower buds to promote leafy growth instead of flowers and seeds.

Plants not pruned tend to get leggy and lose their shape. This can happen with indoor plants during winter so give them more sun or supplement with artificial light.

Propagating Coleus

Coleus plants can be propagated by taking stem cuttings. Gather a sharp scissor, potting mix, small pots with plastic covering, and rooting hormone, and follow these steps:

1. Use a sharp, sterile scissor to cut a 4- to 6-inch long stem making the cut beneath a leaf node.
2. Remove leaves from the lower half of the cutting leaving one or two at the top. Large leaves can be cut in half to facilitate rooting.
3. Dip the end of the stem in rooting hormone compound to cover the bottom leaf nodes. Plant in moistened potting mix.
4. Cover the container with plastic, making sure the plastic doesn't touch the cutting.
5. Place the covered cutting in a bright, warm location with a temperature at 70°F.
6. Keep soil consistently moist. Roots develop in two to three weeks.
7. Remove the plastic and continue growing the new plant in a bright, warm location.

How to Grow Coleus From Seed

It's easy to grow coleus from seed. It takes about 21 days for germination and then three or four weeks of warm weather for fully grown plants. Modern coleus varieties sold in stores are hybrids grown from cuttings potted up for nursery sale, but you can still find seeds of many varieties. For planting outdoors, start seeds indoors about eight to 10 weeks before your last frost date. Here's how to grown your own plants from seed.

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

Potting and Repotting Coleus

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

Common Pests & Plant Diseases

Groundhogs and young rabbits will nibble your coleus leaving them with an unsightly ragged appearance. Protect plants early in the season to deter pests. Watch for mealybugs, aphids, spider mites, whiteflies, and slugs. Insects can sometimes be controlled with a strong spray from a garden hose. Mulch discourages slugs.

Coleus is not usually bothered by disease. Cool, damp weather can lead to fungal disease like powdery mildew. Good drainage discourages root and stem rots.

Common Problems With Coleus

Coleus is a reliable, showy foliage plant with few problems. Fungal infections can set in during periods of cool, humid weather. Here are a few issues that may crop up.

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.