Coleus plants, made popular as Victorian bedding plants, made a huge comeback in the 1990s and show no sign of fading back into anonymity. These lovely plants give us all-season color in full sun, shade, and everything in between and are the ultimate low-maintenance plant. Coleus are tender tropical plants, native to areas bordering the equator. They love the heat but will happily grow as annuals in just about any garden.
- Botanical name: Solenostemon scutellarioides cvs. (Pronounced sol-en-oh-STEM-on scoot-el-lar-ee-OY-deez)
- Common name: Coleus
- Foliage: Coleus are in the Lamiaceae, or mint, family and have the 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.
- Flowers: The tall, thin stalks of flowers are usually pruned off before they bloom, to keep the plant’s energy going toward producing a bushy plant. Because the modern sun-coleus types do not grow true to seed, the incidental flowers are not missed.
- Mature size: Miniature coleus varieties grow only a few inches tall, and others can grow several feet tall. In fact, coleus are often trained to grow as standards through careful pruning. To do this, you would either need to be in zone 11 or have somewhere to overwinter your plants indoors.
- Sun exposure: Light exposure depends on the variety. The old-fashioned seed-grown coleus do best in partial shade, but the newer vegetatively cultivated varieties have their best color if grown in full 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.
- Soil pH: 6.0–7.0
- Hardiness zones: These tropical plants are hardy only in United States Department of Agriculture hardiness zone 11, but they are fast-growing annuals and can even be grown as houseplants.
- Bloom period: Plants will try to bloom intermittently throughout the growing season, but as mentioned, the flower stalks are usually trimmed off.
Modern coleus varieties are hybrids that are grown from cuttings, but you can still find seeds of the older, shade-tolerant varieties. Start seeds meant for the garden indoors about 8 to 10 weeks before your last frost date. If you are growing them as houseplants, you can start seed anytime.
Coleus 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. Coleus are said to prefer a neutral to slightly alkaline soil pH, but as long as there is plenty of organic matter, your plants should be fine.
Care and Maintenance
Although coleus plants love heat, they also need moist soil. 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 cedar mulch can be toxic to coleus, so don't put that around these plants. Also, don't let it touch the stems, as it can promote rot and hide slugs. If you have rich soil, you may not need to feed the plants at all. If not, use a balanced fertilizer 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 the stalks and getting the same results as pinching the tips. Other than keeping your plants trimmed, the only real maintenance required is ensuring they get plenty of water. Coleus in containers may need watering twice a day.
Coleus turn to mush with the first freezing temperatures. If you want to save plants for next season, you have a couple of options.
Pests and Problems
The biggest outdoor pests are groundhogs and young rabbits. If you can protect your plants early in the season, there are usually other things these animals prefer to eat during the summer, and they will leave your coleus alone.
Coleus are 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.
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 their color or with colors that complement them.
Most coleus plants are a good size for the front of the border, and they look best when planted in groups. Another idea: You can circle your mailbox with them. They look lovely, require minimal care out there, and they don’t attract a lot of stinging insects. Just check the label for the sun requirements and indulge.