Coleus

Shade gardeners rely on foliage color more than flowers to provide color. For continuous color in the shade nothing beats coleus. This easy to care for plant with a wide range of foliage colors and leaf forms is a must for every shade gardener. Coleus is good for bedding and containers. And coleus color doesn’t have to end when cold weather comes because coleus makes an excellent houseplant.  Coleus are fine plants for collectors, since there are hundreds of varieties on the market.

In Victorian times coleus was known as Painted Nettles or Flame Nettles. Coleus has suffered in this century from a confusion of name changes and misnamed plants. The correct Latin name for most ornamental coleus is now Solenostemon scutellarioides, although some other species of Solenostemon have been used to produce newer hybrid varieties. To add to this, coleus is a plant that produces new color variations constantly and different nurseries may have plants with different names that are virtually indistinguishable.

Coleus plants range in size from miniature varieties of about 6 inches to huge plants 4 foot high. They are tender perennials and die in winters below zone 8 if left outside. The leaves of coleus come in every color except blue, and just about any combination of colors. Originally coleus leaves were broadly oval with toothed edges; however there are now tiny, oval leaves, huge, broad leaves, frilly scalloped leaves, lobed leaves, narrow ribbon like leaves and a number of other leaf variations. A common color pattern is for coleus leaves to have a band or row of dots of a contrasting color along the edges of the leaves, but some leaves are solid colors or randomly splashed with color. The stems of coleus are square and coleus plants do produce spikes of tiny flowers, usually lavender, from time to time.

Coleus culture

Coleus is easy to grow from seed or cuttings. Sow coleus seeds in a warm spot about 6 -8 weeks before the last frost in your area. Coleus seed needs light to germinate so don’t cover the seeds, just press them lightly into the seed-starting medium. The seeds usually germinate in about 10 days. Give the baby coleus plants time to develop before you decide if they are colorful enough for you, as the color changes with age. Seed grown coleus is somewhat variable, and if you want a coleus plant looks exactly like one you admire, you can always take a cutting. Coleus roots easily from tip cuttings, either in soil or water.

Coleus is very cold sensitive, so don’t plant it outside until after your last frost. If you want to bring plants inside for the winter bring them in before temperatures go below 40 degrees. Inside, coleus needs a warm room and plenty of sunlight to remain vigorous.   If the plants get woody indoors, start cuttings from young shoots, to keep the variety going.

Outside coleus prefers shade, or partial shade. In Michigan, zone 5 and lower, coleus is more vigorous and colorful in partial shade, rather than deep shade. Morning or late evening sun, or bright, indirect light would be preferable to midday sun but some sunlight will make the plants more colorful. Coleus will sometimes adapt to sunnier conditions if the plant is kept continuously moist, but the colors of the leaves may look different than a shade grown plant. Plant breeders are working on varieties that will stand heat and sun. Coleus needs to be regularly watered and it prefers a rich, loose soil that is neutral or slightly alkaline.

For healthy, vigorous plants with good color, fertilize coleus with a slow release fertilizer when you plant it or about every other week using liquid fertilizer. Coleus in the house for winter doesn’t need fertilizer from November to March, when growth slows down. Provide good air circulation around indoor plants and while the soil should be kept moist, don’t over water.

You can prune and pinch back coleus to keep it within bounds. Many newer varieties don’t need pinching or pruning to stay full looking, but if your coleus plant is looking lanky, don’t be afraid to pinch it back. Unless you are trying to produce seed, keep the flowering spikes of coleus pruned off. This allows the plant to put more energy into foliage. When the plant is allowed to set seed it may decline and die.

Coleus plants are short lived and won’t be around forever. If you have a variety you adore, take cuttings from it on a regular basis and discard older plants when they become woody.  Cuttings will root in water or potting soil.  The biggest problem that coleus plants have is with insects chewing holes in the leaves. You can ignore the problem in a garden setting as it is seldom fatal, but if you are growing coleus for show you may want to treat them with a systemic insecticide. Inside coleus may suffer from whitefly, spider mites and mealy bugs, and may need to be treated with insecticides, as there are no natural predators inside. If spider mites are a problem try increasing the humidity around the plants.

Choosing varieties

There are hundreds of named varieties of coleus. Some common mixtures include the Wizard series, which has a variety of bright colors on compact plants, and the Carefree series, which has a variety of colors with deeply lobed leaves. The Solar series are plants that tolerate heat and sun.  The Under the Seas® collection features a number of pretty, mostly ruffled leaved  coleus varieties named after sea creatures.

 ‘Kong Mosiacs’ have huge leaves mottled with colors, each leaf is different. ‘Alabama Sunset’ is a sun tolerant variety in red and orange shades. ‘Black Dragon’ has velvety, heavily crimped, almost black leaves marked with scarlet. ‘Pineapple’ has pineapple yellow leaves and burgundy leaf veins and stems. ‘Darth Vader’ is tall, with long, narrow leaves of purple with a lime edge. ‘Tigerlily’ is a ruffled blend of apricot and peach ‘Duckfoot’ has tiny, deeply lobed purple leaves on a 6-inch plant. ‘India Frills’ is a tiny, purple-pink blend with a trailing habit.