Growing heirloom tomatoes in the garden gives you a chance to save the seeds for replanting each year. Unlike hybrid tomatoes, heirloom varieties produce viable seed that grow into plants true to the parent plant. Tomato seeds require special handling after harvesting, as they are stored in a jelly-like pulp in the fruit and they must be separated from it before storage. The process takes some time but isn't difficult, making tomato seeds a good choice for the novice seed-saver.
Cut the tomato in half, revealing the pockets inside that are filled with seeds and pulp. Scoop the seeds and pulp out of the tomato halves with your fingers. Use the remaining tomato flesh for eating.
Place the pulp and seeds inside a glass jar. Fill the jar with lukewarm water and set it aside for two to three days to ferment.
Drain off the excess liquid once the pulp rises to the surface of the water and the seeds sink to the bottom. Remove the seeds from the jar and spread them out on a paper towel to dry for one week. Brush any remaining pulp off the seeds once they are dry.
Place equal amounts silica gel and seed into an envelope. Silica gel is available from florists.
Place the envelope in a glass jar and let the seeds remain with the silica gel for seven to 11 days. This removes any remaining moisture from the tomato seeds.
Remove the silica gel from the envelope. Replace the seeds in the jar and store them in a cool, dry place until you are ready to replant. A refrigerator offers the appropriate temperature range for long-term storage.