Coleuses are best known for their bright variegated foliage guaranteed to brighten any home or greenhouse, and when planted in the right environment, they can also flourish outdoors. While most coleuses are bought from greenhouses as seedlings or full-grown plants, they are also easy to grow from seeds. Indoors, coleuses require a southern-facing window or grow lights to perform their best. Outdoors, conversely, they prefer light shade and lose some of the color that makes them famous in bright sunlight.
Keep the flower spikes on coleus pinched off to encourage the plant's energies into the foliage. The flowers are not significant and tend to lead to the plant's death. With proper care, coleus can provide a spot of color in your home or garden for many years.
Many think that the best way to buy a coleus is full grown, when the characteristic colors and variegations are established. However, since coleus is influenced significantly by its growing environment, you can experiment with seedlings and get a variety of different plants. Light is the most important factor in the coleus' color. While most outdoor versions prefer light shade, new varieties have been developed for sunlight. Inside, fluorescent grow lights bring out the most intense colors.
Coleus cannot tolerate frost so should not be planted outdoors in areas where temperatures fall below freezing.
Coleus seeds are readily available and contain a number of colors per package. This is a good option if you want many plants or if you want to search for the most colorful variety. You can start the seeds indoors at any time. If you plan to transplant the seeds to the garden, start them at least 10 weeks before the expected last frost date. Sow the seeds in a layer of moist sterile potting soil and cover with a thin layer of fine soil. Cover the tray with a plastic or a sheet of glass to hold moisture in and create a mini-greenhouse. Keep the plants in temperatures ranging from 65 to 75 degrees Fahrenheit. Place in a bright place but not in direct sun. When the seedlings are large enough to handle, thin them out and plant each in its own peat pot. Never handle coleus seedlings by the stem as this can damage them. Only handle them by the leaves. Plant in your garden when all danger of frost is past.
If you want to make identical coleuses, perhaps to use to create a uniform color spot, you can make softwood cuttings of your favorite plants. Use a sterilized razor blade to take cuttings about 4 inches long. Remove all flower stalks and all but the topmost 2 or 3 sets of leaves. Use the razor blade to make a diagonal cut at the base of the stem. Dip the stem in rooting hormone, following the directions on the package. Insert the stem into a peat pot full of wet, well-draining potting medium. Water well until water runs out the bottom of the pot. If you live in a cool climate, put the cuttings in a plastic bag to keep them warm and moist. Keep the cuttings moist for about 3 weeks or until the root systems are well developed. At this point you can repot them into larger containers. Cuttings taken in the fall should be used as house plants. Take cuttings in February or March for transplanting to the garden.