Coleus plants, made popular as Victorian bedding plants, made a huge comeback during the 1990s and show no sign of fading back into anonymity. These lovely foliage plants give us all-season color in full sun, shade, and everything in between and are the ultimate in low maintenance. Coleus is a tender tropical plant, native to areas bordering the equator. It loves the heat but will happily grow as an annual in just about any garden.
Coleus plants are in the Lamiaceae, or mint, family, characterized by square stems and opposite leaves. However, the foliage can vary widely, in shape, style, and color. Breeders regularly produce new introductions with ever more unusual colors and patterns. The tiny blue to white flowers are insignificant, and most growers pinch them off to keep the plant's energy devoted to leaf production.
Planted outdoors in early spring, coleus quickly grows to full size in a single season. It also makes a good container plant and can even be grown indoors. Its vividly colored foliage adds a decorative touch to patios, window boxes, and indoor spaces.
|Botanical Names||Plectranthus scutellarioides|
|Plant Type||Herbacious perennial (usually grown as an annual)|
|Mature Size||6 to 36 inches tall and wide|
|Sun Exposure||Part shade to full shade|
|Soil Type||Rich, moist, loose soil|
|Soil pH||Slightly acidic to neutral (6.0 to 7.0)|
|Flower Color||Blue to white|
|Hardiness Zones||10 to 11 (USDA); grown as an annual everywhere|
Coleus plants are not at all frost-tolerant, so don’t rush to get your plants in the ground. Wait until temperatures remain reliably above 60 degrees Fahrenheit before you move them out in the garden. They will do best in rich, loose soil, so amending with compost or peat moss before planting is advised unless you have very good soil.
To grow coleus in a container, start with a large pot that the plant can grow into; otherwise, you'll be repotting this fast-growing plant before you know it. In mixed container plantings, coleus usually serves as an upright "thriller" plant in the center of the container, surrounded by "fillers" and "spillers."
Coleus is a classic part-shade to full-shade plant, but light exposure depends on the variety. The old-fashioned seed-grown coleus does best in part shade to full shade, but the newer cultivars have their best color if grown where they can receive more sun. However, it also depends on your climate. If you live in a hot, dry area, all types will need some shade, especially in the afternoon. In cooler areas with shorter seasons, the shade coleus will need more sun exposure to help them warm up.
Plants grown in containers indoors usually get plenty of light from indirect sun during the warmer (brighter) months but may need to be exposed to filtered sunlight during the winter. It doesn't take much, but they do need some light.
Coleus prefers a consistently moist, rich, loose soil. Before planting, amend the soil with compost or another organic material. For potted plants, any good-quality peat-based potting mix will work fine.
Container-grown coleus love the loose texture of potting soil, and it always helps to start with a quality mix with a slightly acidic to neutral pH of 6.0 to 7.0. Provide drainage in the pot to ensure the soil isn't constantly wet, which leads to root rot.
Coleus plants grow best in soil that is consistently moist though not soggy. The soil should not remain wet all the time, but long dry spells will slow the plants’ growth, and the leaves will start to turn brown around the edges. Mulch will help the soil retain moisture longer, but don't use cedar mulch, which can be toxic to coleus. Also, don't let the mulch touch the stems, as it can promote rot and hide slugs.
Coleus in containers may need watering twice a day during hot weather. Outdoor containers may require water twice a day. Indoor plants need water only once every two or three days, or a bit more if you live in a dry climate. When using terra cotta pots, it helps to line the pot with plastic to help retain moisture in the soil.
Temperature and Humidity
As a tropical plant, coleus thrives in hot, humid conditions. In temperate climates, the barest hint of frost will spell the end of the plants. Make sure to take cuttings of any favorite plants before the weather turns cold.
Keep indoor plants away from air conditioner vents and other cold spots. In dry climates, the plants will like some humidity from a humidifier or a bathroom environment. To take potted plants outdoors in spring, wait until the temperature is 70 degrees Fahrenheit or warmer.
If you have rich soil, you may not need to feed coleus plants at all. If you have poor soil, give the plants a monthly feeding with a balanced fertilizer mixed at half strength. You’ll get the best color from your coleus leaves if you go easy on the fertilizer.
Container-grown plants can benefit from a slow-release fertilizer added to the potting soil when starting a new pot. Thereafter, feed with a diluted liquid fertilizer given every one to two weeks. Container plants generally need more feeding than garden plants because frequent watering washes nutrients from potting soil.
There are many dozens of coleus cultivars available with various colors, leaf textures, and patterns. Additional cultivars are developed each year, and garden centers tend to focus on a select few that have proven to be most popular among their customers. You may have to shop several different nurseries or online retailers to find the most unique varieties. Some to look for include:
- Wizard series: These are small 12- to 14-inch plants in standard color mixes. They are known to be very easy to grow from seeds.
- Kong series: These coleus varieties have huge 6-inch leaves on big 2-foot plants. They are quite sensitive to direct sunlight.
- 'Black Dragon': This unusual variety has deep burgundy leaves with ruffled edges. They grow to 18 inches tall.
- Premium Sun series: These cultivars are bred to tolerate full sun.
- Fairway series: These are dwarf coleus varieties, only 6 to 10 inches tall, in a variety of leaf patterns and colors.
Is Coleus Toxic?
Some, not all, coleus plant varieties contain diterpene coleonol, a compound that is toxic to animals. Unless you can confirm your plant is not toxic, it's best to keep it away from pets. If you suspect your pet has eaten any part of a coleus plant, contact a vet for recommendations.
Symptoms of Poisoning
Ingestion by animals can lead to the following symptoms: diarrhea, vomiting, bloody stool, lethargy, weakness, lack of appetite, and difficulty breathing.
To get full, bushy plants, pinch out the growing tips when the plants are about 6 inches tall. You can do this a few more times if you like, but after the plants start sending up flower stalks, you’ll be pinching out these stalks and getting the same results as pinching the tips.
Plants that are not pruned tend to get leggy and lose their nice shape and dense foliage. If legginess is a persistent problem, the plants may need more sun. This is most common with indoor plants during winter; give them a bit more sun or, if necessary, artificial light.
Favorite coleus plants can easily be propagated by taking stem cuttings and rooting them. Cut a 4- to 6-inch stem tip, then remove all leaves from the lower half of the cutting. Dip the end of the stem in a rooting compound, then plant it in moist potting mix so the soil covers the exposed leaf nodes. Place the container in a plastic bag, making sure the plastic doesn't touch the cutting. Place the covered cutting in a bright, warm location until new roots develop; this takes two to three weeks. Remove the plastic and continue to grow the new plant in a bright, warm location.
More exotic cultivars can be reluctant to root, so with these, take plenty of cuttings to ensure that you get enough viable plants.
How to Grow Coleus From Seed
Modern coleus varieties sold in stores are hybrids that are almost always grown from cuttings potted up for nursery sale, but you can still find seeds of many varieties. If you will be planting the coleus in the outdoor garden, start seeds indoors about 8 to 10 weeks before your last frost date.
Lightly sprinkle the tiny seeds over a tray filled with potting mix, then lightly cover with a sprinkling of soil. Cover the tray with plastic and set it in a bright, warm spot until seedlings sprout, which takes about two weeks. Remove the plastic and continue to grow the seedlings while keeping the soil moist.
When two sets of true leaves appear on the seedlings, carefully transplant them into their own pots and continue growing them until outdoor planting time. It can take as long as 21 days for the seeds to germinate, so be patient. Once seedlings appear, three or four weeks of warm weather turns them into fully grown plants.
The primary outdoor pests for coleus are groundhogs and young rabbits. If you can protect your plants early in the season, these pests will usually turn their attention to other plants by mid-summer.
Coleus is not usually bothered by diseases unless the weather turns cool and damp. If that happens, expect to see signs of fungal diseases such as mildew. If you are growing your plants indoors, watch out for scale, whiteflies, and especially mealybugs.
Landscape Uses for Coleus Plants
Coleus is normally used as an annual bedding plant or in outdoor container gardens and baskets. In colder zones, container plants are sometimes moved indoors to overwinter. Warmer zones can grow coleus as garden perennials, where they can grow to resemble small shrubs with thick woody stems. When planted in the ground, coleus plants are often massed for dramatic impact; they can also be used as edging plants.
Design-wise, it’s hard to go wrong with coleus. Large quilt-like plantings of assorted coleus can look luscious. They also mix well in borders and containers. You can match the leaves with flowers that echo or complement the coleus' colors.