Coleus plants, made popular as Victorian bedding plants, made a huge comeback during 1the 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 low-maintenance plant. Coleus is a tender tropical plant, native to areas bordering the equator. They love the heat but will happily grow as annuals in just about any garden.
Coleus plants are in the Lamiaceae, or mint, family, with the same familiar square stems and opposite leaves. However, the foliage offers a great deal of variety, with some ruffled, others elongated, and a vast combination of colors and markings. 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.
Coleus has been in cultivation for many years and has had its scientific name reassigned several times. Most sources now label these plants as Plectranthus scuttellariodes, but they have also been known in the past as Solenostemon scutellarioides and Coleus blumei. And there is yet another recent proposal to reassign the group to Coleus scutellarioides. Thus, you may see this plant labeled in the trade under any one of these Latin names.
|Botanical Names||Plectranthus scutellarioides (also known as Solenostemon scutellarioides, Coleus blumei, and Coleus scutellarioides.|
|Plant Type||Herbacious perennial (usually grown as an annual)|
|Mature Size||6 to 36 inches tall; similar spread|
|Sun Exposure||Part shade to full shade|
|Soil Type||Rich, moist, loose soil|
|Soil pH||6.0 to 7.0|
|Bloom Time||Seasonal bloomer|
|Flower Color||Blue to white|
|Hardiness Zones||10 to 11 (USDA); grown as an annual everywhere|
|Native Area||Tropical and subtropical Asia, Malaysia|
How to Grow Coleus
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.
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 vegetatively cultivated varieties 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, shorter-season areas, the shade coleus will need more sun exposure to help them warm up.
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.
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.
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.
If you have rich soil, you may not need to feed coleus plants at all. If you have poor soil use a balanced fertilizer mixed at half strength monthly. You’ll get the best color from your coleus leaves if you go easy on the fertilizer.
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.
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.
Growing in Containers
In pots and other containers, grow coleus in any peat-based potting mix placed in a pot with good drainage. In mixed plantings, coleus usually serves as an upright "thriller" plant in the center of the container, surrounded by "fillers" and "spillers." Grown in pots, coleus will require a lot of water (at least daily, in hot weather) and feeding every month with diluted liquid fertilizer.
If bringing potted coleus indoors for the winter, give it a spot where it receives bright morning light but is shaded from direct afternoon sun. Feed it with diluted fertilizer every two weeks, and keep the stem tips and flower shoots pinched off, which will keep the plant bushy and full.
Growing From Seeds
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.
Common Pest/ Diseases
The biggest outdoor pests 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.
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 just assorted coleus can look luscious. They also mix well in borders and containers. You can match the leaves with flowers that echo or complement them.
Varieties of Coleus
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.
- 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.