As with all produce chosen for seed saving, tomatoes must be fully ripe. That means the fruits (and, yes, they are fruits) have to be fully colored up. And that they weren’t hybrids, of course. Choose true award winners! The fruits should display the special characteristics that make you want to save their seeds. Pick those with the most perfect shape and color from the healthiest plants you have. For instance, if you’re growing several “German Johnson” plants, choose fruits from the most vigorous vines, not from plants that didn’t grow well, showed signs of disease, or suffered insect attack more than their brethren.
Tomato seeds are encased in a gelatinous covering that prevents their sprouting inside the fruit. You must remove this coating via fermentation before you can save the seeds. Slice open two or three fruits of the same variety and squeeze the seeds and juice into a bowl. Add about half as much water as tomato juice and allow to stand in the open at room temperature for three days.
You might want to choose an out-of-the-way place to perform this task because mold will form on the top and it may become fairly odoriforous. Stir twice a day and then add more water and stir very well. Let it rest for a minute, then skim the surface for nasty stuff and floating (hollow and useless) seeds. Pour the good seeds that sank to the bottom into a strainer and rinse them until all the juice and residue are gone. Toss them gently to remove most of the water, repeatedly blotting the strainer’s exterior with fresh paper towels until all the water is gone. The seeds need to be fairly dry to start with or they might sprout. (If they do, eat the sprouts and try again.)
You can then empty the seeds onto a ceramic or plastic plate and place them in a warm, dry area; I prefer to dry mine in a small strainer suspended in the air. (See “Tips on Drying & Storage” for more on this technique.) Either way, stir the seeds once or twice a day to prevent clumping and store them in their envelope when sample seeds snap easily in half.
