Starting your own tomato transplants from seed gives you a greater choice of variety and is much cheaper than buying nursery seedlings, especially if you need multiple plants. Many tomato varieties, especially heirloom types, are only available to the home gardener as seeds. Start tomato seeds indoors four to six weeks before the last expected frost date in your area. The plants are larger and better adapted to handle the rigors of outdoor growing when given a head start on the growing season.
Fill seed starting pots with a sterilized, quality potting mixture. Fill the pots up to 1 inch from the rim and then moisten the soil with water evenly.
Sow two seeds per pot, at 1/2-inch depth. Cover the pot with a plastic bag and place in a warm (65 F to 70 F) room to germinate.
Remove the plastic bag once sprouts appear, approximately seven to 10 days after sowing. Place the seedlings in a sunny window for six hours a day or under grow lights for 12 hours daily.
Keep the soil moist at all times, but not soggy. Water as needed to provide soil moisture and avoid getting the leaves wet as this may lead to fungus.
Thin each pot to the strongest seedling once the second set of leaves grow in. Cut off the weaker seedling at the soil surface using small scissors.
Transplant outside once all danger of frost has passed and seedlings are approximately 5 inches tall. Plant the tomato seedlings in the garden 1 to 2 inches deeper than they were in their pots.