Coleus is one of those plants that appeals to many gardeners because does quite well in the shade. It is also easy to grow from seed and to propagate from cuttings.
4" x 4" container or cottage cheese carton with a few 1/4" holes in the bottom
light seed starting mix
Step 1: Planting and Sprouting
Fill your 4" x 4" container, or containers, to within 1/2" of the top with a loose starting mix and give it a couple taps on the work surface to settle the soil mix. Scatter the coleus seeds over the surface as evenly as possible. Coleus seeds are very small so you might want to empty the seeds into your palm and, using the thumb and index finger of the other hand, take a pinch and scatter them by rolling the seed out from between the fingertips. When the seeds are sown, give the container a gentle shake to settle them. DO NOT COVER the seeds.
DO NOT WATER from the top. Set the container in a shallow container of warm water to allow water to be absorbed into the soil mix. This may take an hour or more. When the soil starts to look moist on top, remove the container from the water and set it aside to drain any excess water.
Insert the container into a clear plastic bag and fold the bag over to create a mini-greenhouse for the coleus. Place the closed bag in a warm, bright location but not in direct sun. You should have seedlings up in a week or two. When the seeds start to sprout you need to remove the container from the plastic bag or they may all die from damping off disease. This is a fungus that forms on the surface of warm, damp soil.
No direct sunlight, just a warm, bright location. Continue to care for the seedlings for another 5-6 weeks. The seedlings will be a little crowded for a while but just be patient.
Step 2: Transplanting Seedlings
After 5-6 weeks your coleus seedlings will be ready to be transplanted. Give the plants a good watering and wait a few minutes for the soil to become loose. Gently tip the contents of the 4" x 4" container into a tray. Take care not to crush or damage any of the stems. Carefully break the soil apart into clumps.
Place about 1/2" of dry soil mix in the bottom of the cells or 4 or 6-packs. Very gently place a plant in each cell and fill the cells with soil. Grasp the seedlings by the leaves to avoid crushing the stems. Set the pack in a container of water until the soil has absorbed enough water that the soil surface is damp. Remove the pack and place it in a tray or other container in a bright location. No direct sunlight and do not over water.
The newly transplanted seedlings will look pretty sad for a couple days but will perk up as their roots get reestablished and begin to take up water and nutrients.
If the larger plants start to get too tall you can snip off the tops and place the stems in water to root them for more plants. You can also root them in Perlite or damp sand. See my Instructable on rooting impatiens.
Don't worry about having 50 or more plants. Whatever you don't use will be appreciated by gardener friends. Take extras to work and mark them FREE. I'll bet they don't last the day.