When home gardeners see Coleus plants, they usually think about the large houseplant that their grandmother owned, or the plant that they learned to root in water in a school science experiment. According to the National Garden Bureau (ngb.org), “Coleus has a long history of use in our gardens as a foliage plant and has gone through various phases of popularity over the past couple of centuries. The relative ease of establishment after planting combined with a wide range of selections has made coleus indispensable in the garden and popular in the container as well.”
Coleus is thought to originate in Southeast Asia. The National Garden Bureau notes “While there is some debate as to when it arrived in Europe, Dutch botanist, Karl Ludwig Blume, is credited with naming and introducing the plant in mid-19th century England.”
A member of the mint family with its square stem, coleus is an easy plant to grow without a lot of pest problems. They are prized for their colorful foliage which may combine shades of green, yellow, pink, red and maroon. New introductions of this popular annual have been selected for increased sun and heat tolerance.
Coleuses vary from smaller types that will reach only 1 foot tall to tall bushy types of 3 feet. Sprawling types suitable for hanging baskets and wall plantings may spread up to 3 feet or more. Most coleus grow fairly rapidly to their full summer size. They are all tender annuals throughout Georgia and will be killed by the first frost.
The brilliant and widely varied colors of coleus foliage makes it a natural for use as a summer landscape bedding plant and as a color accent. During Victorian times in the 19th century, “carpet bedding” landscape plantings relied heavily on coleus for its bright and intricate patterns. Coleus also grows beautifully in containers, which can be used to highlight patios, porches and garden terraces.
Coleuses are highly resistant to serious disease or insect problems when grown outdoors in properly prepared beds or containers. Some insect pests that may show up on coleus include mealy bugs, aphids and whiteflies. Application of a soap spray will control these pests. Some disease problems to watch for include stem rot and root rot. These diseases usually show up because of overwatering.
Most coleus will grow best in part shade or dappled light. However, several sun tolerant cultivars are available that will thrive in full, hot sun. Varieties that are not sun-tolerant will bleach and discolor in full sun. If you are growing coleus from seed check the seed packet for information on sun/shade exposure. If buying transplants look on the plant label.
Coleus must have good soil drainage. Poorly drained soils and excessive watering will damage coleus. Plants suffering from “wet feet” will be stunted, leaves will turn a muddy brown, and leaf margins will be scorched brown. The plants should not be allowed to dry out, however. When transplanting coleus plants water in thoroughly at planting. During the first seven to 10 days, keep root balls moist but not overly wet. Thereafter, water only when top inch of soil is dry (check with your finger every three to five days). Use of soaker hoses is highly recommended.
Coleus grown in containers are more susceptible to drying out and should be planted in a very well-drained soil mix that is watered more frequently. Pinch growing shoots of young plants frequently to encourage and maintain dense foliage. For a midsummer growth boost, fertilize in June, July and August with a liquid fertilizer at half the usual dilution.
Flower spikes will appear in late summer. Many people dislike their appearance, and if the flower spikes are allowed to go to seed the plant will decline. Shear back flowers to extend performance. As compared to seed started coleus vegetative coleuses are sterile forms that must be grown from cuttings. They generally, flower little in the summer and require less maintenance than seed-grown coleus. Since coleus are annuals and will be killed by the first fall frost, you may want to take cuttings of especially prized cultivars. They root easily from stem cuttings at any season. Common coleuses can also be grown from seeds. Happy Gardening!