I’VE ALWAYS JUST SMEARED the seedy innards of heirloom tomatoes on paper toweling, let them dry, and then stored them for the coming year–maybe rinsing the stuff in a strainer first, maybe not. That’s how to save tomato seeds the easy way. But fermenting the goopy gel and juice first for a few days offers some important benefits: The process may reduce some seed-borne diseases, and it also breaks down a germination-inhibitor in the gelatinous matter around the seed. (It also smells really bad, so pick your location wisely!) The story (also in podcast):
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HOW TO SAVE TOMATO SEED was the subject of this week’s podcast with Robin Hood Radio of nearby Sharon, Connecticut, the smallest NPR station in the nation. Stream it now, or subscribe free on iTunes or the Stitcher app so you never miss another episode. Or just get the Robin Hood RSS feed if you prefer. Either way, look for the September 17, 2012 edition.
Like everything in gardening—a pursuit I always remind myself is part art, part science—experts differ on just how to save tomato seed. I’ve listed links to some variations below. But basically, here’s the idea:
1. Working with one variety at a time, select fully mature fruits to collect your seed from. The fruits you use should be true to type for that variety—not the runts, and not oddities like double fruit. Seed Savers Exchange says to avoid the first fruit from large-fruited varieties, too.
Suggestion: If you’re going to save a lot of tomato seed, plan to do this when you are making soup or sauce or maybe gazpacho, because there will be lots of tomato flesh that would otherwise go to waste.
2. Simply cut the fruits in half or quarters, then squeeze the insides—juice, gel, seeds, pulp—into a wide-mouth container. With large fruits, prevent splatter from going everywhere by using a bowl to catch the innards, then pour the results into jars.
3. Whether to add water to the expressed materials is a subject of disagreement. I don’t—but in the case of the variety up top, of which I had just one big fruit shared by a friend—it would have made the process easier. If you do add water, don’t use more than the amount of tomato innards that you have.
4. Cover the jar with a piece of paper toweling and an elastic band to keep insects out. Again, this process really stinks, and will attract them.
Allow to ferment for several days in a spot that’s ideally “room temperature,” but not more than 70 degrees F. But hey, it’s usually summer when you do this, so temperature control is tricky. Avoid cooking the stuff in a hot, sunny spot! The garage might work, and spare you the funky fumes.
5. Shake or stir the jars daily, though some people also skim off the foam each day, some wait till three to five days have elapsed and do it just once. Hollow, non-viable seeds will supposedly float upward in the process, so you’ll be eliminating dead seed, too–or so some experts say.
6. After about four days, skim off and discard the fermented, foamy mess on top, then pour the remainder through a strainer and rinse thoroughly. Let excess water drain off; maybe give the strainer a few thumps in the counter to help.
7. Spread seeds onto paper plates that are labeled by variety. Don’t use plastic or glass or china plates; you want to wick excess moisture away from the seed, meaning paper is the better choice. Allow to air dry thoroughly, which will take several weeks, before storing.
ALL OF THIS ASSUMES you are saving heirloom varieties—not hybrids, which won’t “come true” from their own seed. It also assumes that your plants didn’t experience any cross-pollination that would taint their seed.
“Cross-pollination between modern tomato varieties seldom occurs,” says Seed Savers Exchange, “except in potato-leaf varieties [such as 'Brandywine,' 'Stupice,' or 'Pruden's Purple'] which should be separated by the length of the garden.” Estimates of how far that is range from 25 to 50 feet or more. Like so much else in this gardening business, apparently it’s a matter of opinion.
how the experts save seed: