Harvesting and Processing Seeds
Seeds must be mature before they are harvested. Therefore, seeds need to be gathered after the fruits and pods have ripened, but before they rot. Different methods of harvesting and processing seeds depend on the plant species and the fruits or pods involved. Having a familiarity with the methods will help you to be successful.
Drying
After gathering your seeds, process them if needed, and then clean, rinse, and drain them. The final stage before you store your seeds is to dry them thoroughly, which takes a few days to a week. Some seed savers dry seeds using china or plastic plates. Others use newspapers or other paper products, although they run the risk of having their seeds end up glued to the paper. Still others use screens, because screens have the best ventilation. Whichever type of container or surface you choose, scatter your seeds carefully, to keep them from drying in pairs or clumps. Small seeds that can shatter or blow away can be encased in fine mesh or a paper bag. Leave your seeds in a dry place where the temperature will stay even and below 90°F. Higher temperatures can kill many seed varieties. Be sure to stir your seeds around and turn them over so that all of their surfaces get exposed to the air.
If your seeds begin sprouting, the drying process has been too slow, and you will have to start over again. You may need to switch to screens or use a fan to improve ventilation. Don't use heat to speed up the drying process; it may kill your seeds. When your seeds are brittle and hard, but not dried out, you can put them away.
Storing The Seeds You Have Saved
Now that you have successfully gathered and dried your seeds, do not negate all of your hard work by storing them incorrectly. Store your seeds where they will remain cool, in the dark, and dry. Many people place their seeds in their refrigerators.
By hand, gently rub off any chaff. Then store your seeds in simple paper envelopes (except for beans, peas, and other legumes, which should be stored in breathable bags). Be sure to seal and carefully label each envelope or bag with the variety, date, and any other pertinent information. Avoid opening packages until you are ready to plant; otherwise, moisture may dampen your seeds or cause them to mold.
Your seeds will "hibernate" happily all winter long, provided you have stored them in a cool, dark, dry, and rodent-free place. The day before you intend to do your planting, take the seeds out of storage so they can warm to room temperature. From then on, treat them in the same manner as your store-bought varieties.
The seeds you have saved will germinate best the following year. Thereafter, germination rates will decline depending on the quality of the original seeds, the types of seeds, and their storage conditions. In the end, it is best to replant, and then select the best plants for seed saving each and every year.
–Taken from Heirloom Seeds article, originally published in the 2006 Farmers' Almanac, written by freelancer Jean Grigsby.