Want to Save Seeds? Here's How to Do it
If you've got an edible garden, chances are you've contemplated saving your own seeds. Socio-political reasons aside, there are many practical reasons to do it: You can maintain your stock of favorite and rare varietals, without having to re-buy every year, and you can also create some really outstanding fruits and veggies.
Seed saving is a rewarding practice. Each year you harvest the seeds from your very best specimens, process and store them, then plant them again the following year. Over time your plants evolve to thrive in your exact microclimate, and your garden becomes ever more delicious and fruitful.
For saving purposes, seeds are separated into two general categories: dry and wet. Dry seeds come in a pod or husk, as in lettuce, herbs or beans. Wet seeds are hidden inside tasty fruit, such as tomatoes and peppers.
Seeds must be allowed to fully develop. This sometimes means allowing things to mature well beyond the normal (or even edible) harvest point. Tomatoes and peppers are usually harvested ripe, but you'll have to let your basil and lettuce go to seed. If you're collecting squash seeds you need to leave the fruit on the vine until it is woody and hard.
To harvest husk seeds, first let them fully dry out on the plant. Then ever so carefully cut the stem below the husks, insert the cutting into a paper bag, and shake vigorously. If the seeds don't appear fully dry you can place them on a porcelain plate for a few days to finish. Podded seeds can be removed by hand once fully dried and hardened.
Wet seeds have a protective moisture barrier. Ever wondered why tomatoes don't start sprouting in the fruit? These seeds should be processed by fermentation, which dissolves the protective coating and kills seed-borne diseases. To ferment, scrape the seeds out of the fruit. Don't fret about removing all the plant matter, a bit of fruit is perfect to get fermentation going. Put the seeds in a glass and fill with water. After a few days you'll notice lots of mold on top, probably with some seeds stuck inside. Clean floating seeds are bad, and should be removed. Seeds buoyed by plant matter can be stirred back in.
Remove the moldy layer with a spoon and top-up the water. Repeat this process until you have a layer of clean seeds sitting in a glass of clean water. Then dump the water and place the seeds on a porcelain plate to dry. Make sure they aren't touching or they'll stick together permanently.
Good record keeping is an essential component of seed saving. Keep your dried seeds in a sealed paper envelope (coin I envelopes are perfect). Label with the plant, date, and any notes you want to keep on the specimen. Store the envelope in a cool dry place until next year.
Not all seeds can or should be saved. The issue is cross-pollination. An Armenian cucumber can pollinate a cantaloupe. The result will still be a cantaloupe, but its seeds will be hybrid; the second generation will be unpredictable and the third generation will most likely be infertile.
Before going to too much effort, it is worth checking for the specifics of the seeds you want to save; seedsavers.org is a good resource. Fortunately, some of the best stuff is self-pollinating: tomatoes, lettuce, beans, peas, peppers and most herbs. All these make purebred seeds that will produce reliably the following year.
There are two proven ways to prevent cross-pollination: separation and isolation. To separate, put cross-pollinating plants as far from each other as possible. This can be difficult to achieve, however, because some pollen travels for miles and you can't control what your neighbors grow. Isolation is achieved with a bee barrier (like fine netting) over the plant. This keeps intruding pollens out, but also means you'll have to pollinate by hand.
Though cross-pollinators are more effort, some of the rare/expensive specimens might be worth it. You may even get lucky, with none of your neighbors growing similar varietals. Just keep experimenting, maintain good records and don't be afraid to fail! There's also the possibility (albeit slim) that one of your cross-pollinated plants will turn out to be really great. Happy gardening!