Planting vegetable seeds indoors in late winter or early spring will give you a jump on the growing season. This gives you the advantage of a longer harvest season with more produce starting at an earlier date. The time you for planting seeds indoors depends on the type of plant you are growing. It is important to read the seed packet closely to determine the germination rate of the plant. Most vegetable seeds require that you plant them indoors 4 to 12 weeks before the date you want to transplant them outdoors. Plants with a 6 to 10 day germination length will grow large enough to transplant outdoors approximately 5 to 8 weeks from the planting date.
The first step in planting seeds indoors is moistening your seed-starting medium with water. You want it to absorb enough water to become the consistency of a damp sponge. Fill a propagation tray with the moist medium and sprinkle the seeds on top. Verify the planting depth of each type of seed from the seed packet to make sure you do not place too much soil on top. Most seeds do well at a depth of 1/4 inch. Sprinkle medium on top of the seeds instead of pushing them into the soil to get the proper depth. Label the tray with the type of vegetable and variety so you know what you are growing in each tray.
Cover the tray with a piece of plastic wrap to hold moisture in the soil. This will create a greenhouse environment for the seeds to help them germinate. Place the tray in a warm area that does not receive bright sunlight until the seeds emerge from the soil. The top of a refrigerator works well, as long as there is no sun coming in from a close window. Open the plastic cover every day to check the soil moisture. You want to keep it evenly moist, at the same consistency of a damp sponge. Mist the soil with water if it begins to dry out.
Remove the plastic covering from the tray once you see the seedling poke through the soil. Move the tray to an area that receives bright sunlight to promote seedling growth. You will need to watch the soil moisture closely since it will dry quickly in the bright sun. Mist the soil with water as often as needed to keep it moist. Transplant the small seedlings into individual growing pots once they are approximately 2 inches tall. Small six-pack planting containers or 2-inch pots work well for vegetable seedlings. Use a high quality potting soil and moisten it with water before planting. Set the seedlings into the containers slightly deeper than there were growing in the propagation tray to promote strong root growth. Continue to grow the vegetable seedlings indoors until they are approximately 6 inches tall and have a minimum of one set of true leaf growth.
Ohio Farm Bureau Federation: Starting Seeds Indoors
University of Missouri Extension: Starting Plants Indoors from Seeds
University of Kentucky: Starting Plants for Seed at Home