Take the bite out of winter with this fun DIY project. Coleus, a colorful member of the mint family is a good choice for such a winter project because it can be used either as a houseplant or as a bedding plant.
Coleus is such fun to grow from seed because the tiny seedlings show their bright happy colors. Many of them have bicolor or tricolor leaves, with shades of cream, salmon, rose, bronze, copper, chartreuse, scarlet, and yellow. The names of the many cultivars give you some idea of the colors and patterns you can anticipate: 'Paisley Patches', 'Scarlet Poncho', 'Scarlet Dragon', 'Gaslight', 'Highland Fling'. You can truly bring out the vibrancy of the colors if the plant is raised under fluorescent lights.
Coleus grown as houseplants can be started at any time of the year, of course, but those intended for beds outside should be started 10 weeks before your last expected frost so the plants will be well developed when the time comes to set them out.
1. SOW THE SEEDS
Prepare a flat of potting soil. Choose a fine, fluffy, soilless mix rather than the dense stuff that is sometimes sold as potting soil. Air spaces encourage good root development.
Soak the flat well before sowing the seeds—it should be damp but not sopping wet. Always water with lukewarm water; coleus doesn't like cold soil. Be sure to water before planting seeds so they don't float off into the corners.
Slit open the narrow end of the seed envelope and hold it over the flat, tapping lightly to distribute the seeds evenly over the moist surface. Gently press the seeds, but don't bury them under more soil. Coleus seeds need light to germinate, they must be planted on top of the soil.
2. COVER THE FLAT
The flat can be covered with any material that will let light in and retain moisture; a clean sheet of glass or acrylic, a clear plastic bag, or a piece of transparent plastic wrap. Don't envelop the flat tightly, though, because lack of air circulation may encourage damping-off disease or the development of molds.
Place the flat in a spot where light can reach it—but not in direct sunlight, or the seeds will cook. Keep it warm (about 70 degrees) with a pilot light, a hot-water heater, or a soil-heating cable. A tiny magic carpet of colored seedlings should appear in a week.
3. TRANSPLANT THE SEEDLINGS
As soon as the first sprouts appear, move the flat to a place where it will receive day-long light. When the seedlings develop their first true leaves, transplant them into small individual pots or another flat, spacing them two inches (5 cm) apart.
At this point in their development, windowsill or greenhouse light will do.
4. PINCH TO PROMOTE COMPACTNESS
When the plants are about 6-8" high, pinch out the tip of the stem to encourage the plants to form bushy side branches. Then pinch back the branch tips when they reach a length of 6-8".
Outdoors, coleus leaf colors are more brilliant if the plants are set in partial to light shade. Also, compact plants are less likely to blow over in the wind.