SEED LIBRARY CO-FOUNDER DOUG MULLER makes it sound easy, and gross in a fun way—you know, like when you’re 12 years old and “gross” is a good thing, an adjective you say and then giggle delightedly at the slightly naughty notion. The co-founder of Hudson Valley Seed was teaching a group of us how to save tomato seeds, using words like “slimy” and “smelly” and “goopy” and, yes: “gross.” How to save “wet” seeds such as tomatoes, the Hudson Valley Seed way. (That’s one fruit of their ‘Upstate Oxheart’ heirloom variety, above.)
I spent another day at Hudson Valley Seed in Accord, New York one late August, where I gave a lecture as part of their annual farm tour. You can visit them anytime online, and learn about growing vegetables, herbs and flowers and saving their seed on the seed company blog. Because they’re a small farm, they don’t use lots of seed-processing machinery, but rather the kinds of tools a home gardener would use (though maybe the slightly larger size, like the size-XL masher, below).
With wet seeds—ones that come enclosed in a fruit (the part of the plant we eat, such as tomatoes, tomatillos, eggplants, peppers, squash and cucumbers)—the process is roughly the same, though some are “wetter” than others with more obvious seeds.
Yes, you could simply separate seeds from the pulp and skip the smelly-gooey-gross part of the process. But that part–the natural act of fermentation that’s happening in the jars in the photo below–helps break down germination-inhibiting compounds such as the gel sac around tomato seeds, and can also reduce some seed-specific diseases.
Select a few of your best-looking mature fruits from each of your healthiest-looking plants. The variety must be open-pollinated, sometimes called “heirloom,” and not a hybrid. It should also have been isolated from another tomato variety by at least 25 to 50 feet. to avoid cross-pollination. Choose fully mature fruits that look like the variety is supposed to.
If the tomato fruit is a little past peak ripeness, no worry: Nature saves and re-sows her own seed when the over-ripe fruit falls onto the ground and rots in place, Doug reminded us. “We just simulate that,” he says. (Side note: With squash and cucumbers and eggplants, you need to let the fruits get overripe first, probably a few weeks past good eating stage.)
Quarter the tomatoes, squeezing the innards (seeds and pulp) into a container. A large canning jar may be plenty for the home gardener; at Seed Library there are giant plastic tubs in use everywhere (like the one above), full of festering “wet” seed pulp. (Remember he warned us it would be gross!)
Reserve all the tomato flesh in a pot or your food processor bowl, to make sauce or soup or salsa or gazpacho. (With eggplants, squash and cukes, the leftover flesh at seed-saving time won’t be usable as food.)
Add water to your seeds and pulp to create a concoction that’s equal part fruit and water, and set it aside (but not out in the sun; a shed is perfect), covered with screening or cheesecloth to keep bugs away. Allow the mashup to sit and ferment for about three to five days.
Keep a close eye so that it doesn’t go too far and over-ferment! Depending on temperature, timing can vary batch to batch. The clue: Once a smelly scum or mold forms on the top of the mix, it’s time to wash the seed clean, said Doug.
Skim off the mold, in which will probably be floating some seeds. Discard those, too; floating seeds are non-viable, and the good ones will have sunk to the bottom.
Put your mix in a strainer and wash thoroughly. Empty clean seeds into an unwaxed paper plate (labeled as to variety) and allow to dry thoroughly. If it’s humid out, run a fan on low nearby.
Store thoroughly dry seed in a cool, dark spot in an airtight jar—and again, label them!
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