Start coleus seeds now for spring

All this talk about container gardening made me think of a plant that at one time dominated hanging baskets and terra cotta urns all summer.

Coleus is one of my favorite ornamental plants, but since the popularity of Heuchera (coral bells), Calibrachoa (million bells) and Ipomoea (sweet potato vine), coleus seems to have been pushed to the back when it comes to container gardening.

To compete with all of these popular plants, growers have developed even more colorful varieties of coleus. Each spring when I visit garden centers, it never fails that I find a new coleus that is even more brilliant and attractive than what I saw the previous year.

As a container plant, they are amazingly easy to grow. Not only do they root quickly from cuttings, but their seeds are quick to germinate. They grow well indoors until our weather allows for outdoor planting, which is why I bring them up at all this time of year. Now is the time to plant coleus seeds so they will be ready to move outdoors in late May.

It takes about 10 days from the time you first put a coleus seed in the soil before you will see the tiny, new leaves emerge. Plant the seeds in a sterile, soilless medium to avoid the fungal, damping off disease from attacking. Make a mini-greenhouse by placing a plastic covering over the container, but be sure to leave a ventilation hole to avoid mildew and fungus from growing.

Place the container under a fluorescent light and keep the soil moist until the seeds germinate. As soon as you see the tiny leave emerging, take the plastic away and let the baby plants get lots of air. You can back off the water a bit, but don’t let the soil dry out completely. I know I say this a lot, but it is important that the container has drainage holes so the excess water has a place to go.

When the baby plants start to get a bit crowded in their container, it is time to transplant them into their own individual space.

The neat thing about coleus is that no two plants seem to have the same exact vein or leaf designs. In containers or in the garden, use these colorful plants in window gardens, patio containers and as bedding plants to create colorful borders and edgings.

When the plants have about six to eight leaves and the outside temperatures have risen to the point there are no more frosty nights, move the containers outside in a shady spot for a few hours each day. This will help acclimate the plants to the outdoors. Gradually move them into brighter light for a few hours each day and after about two weeks of this, they can stay in their permanent location the rest of the season.

When it looks as though flowers are starting to appear at the tips of the stems, pinch off the top one-third of the plant and it will send out side shoots making it bushier. Just taking off the flowers won’t have this effect, but will also keep the plant from going to seed. Seeds from hybrid varieties will not produce plants that look like its parents.

Unlike many colorful leafed plants, such as Heuchera or Hosta, coleus love sunlight, which seems to brighten their color even more. They don’t require a lot of water after they mature, even though they need it when they are still in the seedling stage. They also don’t seem to be bothered by many insect pests. Mites and whiteflies can be controlled with a good spraying of the hose each morning.

But there is one pest, the mealybug, that can threaten. If your coleus gets an infestation of mealybugs, discard all affected plants and start over. Adult mealybugs look like tiny balls of cotton on the undersides of leaves and there are can several stages of the insect attacking the plant at the same time, which makes it difficult to control with pesticides.

Here’s the fun part. At the end of the season when frost threatens to wipe out the coleus, take cuttings from your favorite varieties. They can be rooted in sterile soil and grown indoor as house plants throughout the winter. Coleus also root quite easily in water and can survive there for quite a while, although once planted in soil it will take them a little longer to get established. I’ve kept coleus going in a glass of water on my windowsill for several months just by refreshing the water as needed.