1. Grow your garden.
2. Choose the best plants—strongest, tastiest, prettiest or most productive—and let them go to seed and ripen fully.
3. Wet-process seeds from wet fruits, like tomatoes, by soaking the seedy pulp 2-3 days in a jar of water, then rinsing.
4. Dry all seeds completely.
5. Store in a container and label.
6. Fill out the return form on the first page of this guide..
7. Return to the library for others and choose your next batch of seeds.
To make sure the seeds you save are the same variety as their parents takes isolation techniques.
Distance: Many easy seeds need just a little distance, 25-50 feet, from other varieties of the same plant to make "true" seed.
Time: Some advanced seeds, especially wind pollinated plants, can be isolated just by saving seed pollinated earlier or later than other varieties.
Barriers: In the home garden, it may be easier to hand pollinate a squash flower and close it to other pollinators than to find 500 feet of isolation.
The library has several good books explaining seed saving.
The Seed Ambassadors have published an in-depth, free on-line booklet on seed-saving.
Seed Matters has published a handy on-line chart of isolation distances.
Plants are divided into families and just a few major families make up our common gardens. If you know the family of a plant, you can make a good guess whether it self-pollinates or cross-pollinates, and so how much isolation you need to give it to get true seed. Here are some of the most commonly found, in order of ease for seed-savers:
Legumes: Beans and peas. Self-pollinating, require minimal isolation distance.
Compositae: Lettuce, sunflower, salisify, chickory, endive. Both self- and cross-pollinate, may require some isolation.
Solanaceae: Tomatoes and peppers. Usually self-pollinating, though peppers require more isolation distance.
Amarylliaceae: Leeks, onions and chives. Some cross-pollination, requires some isolation.
Umbelliferae: Carrots, dill, fennel, celery, parsnip, parsley. Cross-pollinate within species, isolation required.
Brassicas: Cabbage, broccoli, kale, cauliflower, mustards, radish. Cross-pollinate freely across species, require careful isolation techniques.
Chenopodiaceae: Beet, chard, spinach, lambsquarters, quinoa. Wind-pollinated and cross-pollinate very freely, require mechanical isolation (bagging).
Curcurbits: Squashes and melons. Cross-pollinate within species freely, across species occasionally, require careful isolation techniques.
Seeds, kept under ideal conditions, can remain viable several years, even centuries. But without care, they start losing germination rates within a year. Handle seeds gently. Dropping and rough handling can reduce germination rates.
Seeds like to be
Collect seeds in dry weather and dry further indoors, in a brown paper bag or on a cookie sheet, if necessary before storing.
Label seeds carefully.
Many people store seeds in sealed containers in the refrigerator, where it's dark and the temperature is constantly low.