Fall is rapidly approaching in San Diego. We will likely have a few more hot spells, but there is a slight but distinct chill in the air most nights. By now most of the summer garden is winding down. Carrots are huge and waiting to be pulled, pumpkins are developing a nice orange hue, and the tomato vines are ripening the last of their fruits and withering away. Now is your last chance to harvest some seeds and put them away for next year.
Seed saving is a rewarding experience for the home gardener. Grab the best fruit you’ve grown and save its seeds for next year. By doing so, you train your plants to grow and thrive in your exact microcosm. Before you go too crazy though, there are two things to consider: 1) hybrid vs heirloom, and 2) cross-pollination vs self-pollination. Always choose heirloom plants for seed saving; hybrids are almost always sterile. Also stick with self-pollinating plants, as cross-pollination leads to hybrids (see above).
Fortunately, tomatoes are self-pollinating and almost always breed true-to-type. You can harvest seeds from any heirloom tomatoes you like, even the ones you buy at the store. The simplest method is to simply dry the seeds on a porcelain plate. However better results come from running the seeds through a fermentation process.
Have you ever wondered why tomato seeds don’t sprout inside the tomato? Wet seeds typically have a gelatinous coating that keeps them from sprouting. Fermentation dissolves this coating and renders the seed ready to go. It also kills seed-borne illnesses and weeds out “bad” seeds from the bunch.
Actually sometimes tomato seeds do sprout in the fruit, after it has rotted on the ground. Rotting fruit undergoes natural fermentation, as wild yeast and bacteria consume the sugars within. This natural fermentation process can be carried out in the kitchen, resulting in clean, viable, and disease free seeds.
Put the seeds, their gelatinous coatings, and any extra tomato flesh you have in glass with water. The tomato flesh helps kick start fermentation. Make sure you label the glass with the variety you are saving. A sticky note lets the label follow the seeds throughout the process.
After a week you will have a nice layer of mold on the top of the water. Keep spooning out the water to remove all the flesh that is in suspension, taking care not to remove too many seeds. Any clean floating seeds should be removed; they are bad. Seeds that are floating inside large chunks of flesh can be stirred back in. Refill the glass with clean water.
Repeat this process every few days. Each time stir up all the seeds and stuff on the bottom. This will bring the non-seed material into suspension and help you spoon it out. Eventually you will be left with a clear water and clean seeds on the bottom. You must stay on top of this process. If the seeds sit in the clean water too long (more than a few weeks) they will sprout and become useless.
Dump out as much clean water as possible and arrange the seeds on a porcelain plate. Make sure none of the seeds are touching or else they’ll stick together. If you’re lucky, a friend will come over and ask, “Why do you have those seeds arranged so artfully on that plate?” and you will have a convert.
The seeds will be dry after a day or two. Package, label, and store them for next year. Coin envelopes from the office supply store are cheap and perfectly sized.