Although you probably think of flowers for garden color, some plants have leaves as brightly colored as petals. The coleus plant (Solenostemon scutellarioides) is one example that produces large, showy leaves marked by every color except blue. A tropical native, coleus is usually grown as an annual, only growing outdoors year-round in U.S. Department of Agriculture plant hardiness zones 10 and 11. But you needn't say good-bye to a coleus at summer's end; instead, grow it as a houseplant until the following spring or take some cuttings to make new plants.
Pot a mature, outdoor-grown coleus to overwinter as a houseplant in early fall, before a cold snap arrives and damages the frost-sensitive plant. Water the plant well the day before the move to lessen transplant shock and help keep soil around to the roots. Dig up the plant with a shovel or spade, making a circular cut into the soil under the plant's canopy. Gently tip the plant to one side, and slide the shovel under the plant to lift it.
Pot the coleus in a container that has at least one drainage hole and is a bit larger than its root ball, using potting soil to fill any empty space in the pot. Tamp the soil well and flood the pot with water to get rid of any air around the roots.
Starting New Plants
You can also start new coleus plants from a mature plant by taking stem cuttings and rooting them. Because the plant naturally slows its growth in fall, it's best to take cuttings in mid-to-late summer, while weather is still warm and the plant is growing vigorously. Choose healthy stems without flowers or flower buds, and cut pieces about 5 inches long with a sharp knife or shears, cleaning the blades between each cut to prevent spread of plant disease. Remove any leaves from the bottom one-third of the cutting.
Coleus cuttings root quickly in water, usually taking about one or two weeks, or you can root them in moist sand. Once rooted, plant the cuttings in containers filled with moist potting soil, but do this when roots are about 1/2 inch long because longer roots tend to tangle and can be damaged easily.
Although outdoor-grown coleus plants usually prefer shade, they need extra light indoors to keep growing. A sunny, uncurtained window that faces west or south works well provided there's no roof overhang or other structure to block light and the area stays above 60 degrees Fahrenheit throughout the winter. If a sunny spot isn't available, grow the plants about 6 to 12 inches away from a fluorescent lamp with two fluorescent bulbs; use one grow light and one cool-white bulb to give the plants full spectrum lighting.
Water the plant regularly, but allow the top of the soil to dry slightly between waterings to discourage fungal growth, and pinch the growing tips of stems to encourage branching and a bushy shape.
Moving in Spring
When spring returns and night temperatures remain above 50 degrees Fahrenheit, move potted coleus plants back outdoors, but do this gradually. Let the plants acclimate for a week or two by keeping them in a shaded, sheltered spot such as under a roof or overhang, increasing their exposure to light by an hour or two each day. Choose a well-drained area with good air circulation when you're ready to plant the coleus in the ground.