Coleus are a standout family of shade plants that glow in myriad colors and combinations to electrify borders, beds, flower arrangements, and containers. Solenostemon scutellarioides and its hybrids are in the mint family, as you can tell by feeling the square ridged stems. Leaf size varies from 1-8 inches, and they can grow up to 36 inches tall. As a group they prefer indirect light, though there are cultivars for full shade and sun as well. They can also be grown as houseplants or overwintered indoors with the help of grow lights. Their ease of growth has made them popular plants for science experiments to test salt tolerance, water uptake, and more. Coleus roots have been used historically in India to treat heart and lung diseases. Note: Coleus are toxic to cats and dogs.
Choose a site receiving the proper light exposure that suits the variety. Most prefer light shade, but there are varieties for full sun or shade. Outside temperatures should be over 55 degrees F before planting. They like moderate moisture – neither very dry nor soggy. Soil can be neutral to acidic, and of any level of fertility, but should be well-drained. Create a hole twice as wide as your transplant and as deep. Apply slow-release fertilizer per the directions at planting time.
Coleus plants like a perfect spot of moderate moisture – about the texture of a wrung-out sponge. When they get too dry or wet, plants will wilt. Water at least once weekly during the growing season, more in hot or dry conditions. In containers, check the soil and allow it to become dry an inch down before watering. Mulching helps to retain moisture.
Coleus are not heavy feeders. Apply a slow-release fertilizer at planting and possibly once more if your region has an extra-long growing season. You have the option to repeat liquid fertilizer at a dilute rate every two weeks for extra-boisterous growth. Avoid fertilizers with a high phosphorus content, since flowering will hasten the decline of the plant.
To create a bushy plant, pinch the main stem above a growing leaf or bud when the plant is under eight inches tall. Once established, Coleus can get leggy from time to time. If this happens, pinch back the growing tips again to a growing leaf. It’s helpful to prune off flowers if you are growing primarily for the foliage, since once the plant sets seed, it begins to die. You can also create a tree shape or standard form Coleus. Pick a central stem early in the plant’s development and prune of the lowest side shoots to the height you want growth to begin. Then remove any future side shoots that develop below that spot.
Caring For Coleus in Pots
Pick your site to match your coleus variety. The majority of coleus thrive in partial shade, but there are varieties for both full shade or even full sun. The optimal time for planting out is when temperatures are over 55 degrees F. Coleus would like the soil to be barely moist – in other words, never too dry or too wet. Soil can be neutral to acidic, and of any level of fertility, but should be well-drained. Create a hole twice as wide as your transplant and as deep. Apply a slow-release fertilizer per the directions at planting time. In containers, check the soil and allow it to become dry an inch down before watering. Mulching will retain moisture if needed. In regions outside its hardiness zone, when fall arrives, consider taking cuttings or bringing the plant inside for the winter.
Winter Care for Coleus
Only hardy from USDA zones 11 and warmer, Coleus is most often grown as an annual. In regions outside its hardiness zone, in the fall you have the option to take cuttings and propagate or bring the plant indoors until spring.
For indoor container care, use grow lights, or find bright morning light, and keep slightly moist. Coleus doesn't like being overly wet. Make sure the soil is dry to at least an inch before watering again. A humidity tray or misting will raise the humidity level in the air. The biggest risk factors to your Coleus indoors would be lack of humidity and soggy soil.