If you are a beginning seed-saver it is best that you first grow self-pollinating crops that mature and produce seed in one season. These crops are called annuals. Although there is a small chance that cross-pollination with other crops could occur, generally it is easy to save seeds from these crops that will grow true to type. Annual crops that are considered easy for seed savers are: beans, peas, lettuce, tomatoes, eggplants, peppers, and okra. In the Seed Sharing Library the drawers containing Easy Crops will have a green dot.
These are annual crops that produce seed in their first year, but they will cross-pollinate with other crops of the same species. This group includes broccoli, cucumbers, spinach, squash, pumpkins, corn, melons, and Chinese greens. Special techniques have to be implemented to make sure that the seed strain is kept pure. One method is to hand-pollinate the flowers and then tie the blossom shut or put a bag around it to keep out insects or wind-blown pollen. This is most often used with vining plants with large blossoms such as squash, melons, and cucumbers. You can also isolate the plant from others of the same species by using distance (at least several hundred feet), timing (growing varieties that bloom at different times), or by growing only one variety of a species at a time. This works best with crops that are grown in large plots such as corn. The third option is to make a cage out of fine-gauge netting or screen and cover the entire plant, which is fine for more compact plants such as broccoli and spinach. Remember you do not have to cover, tie or bag every flower of every crop, just from the plants from which you are saving seed. In the Seed Sharing Library the drawers containing Intermediate Crops will have an orange dot.
The most advanced crops from which to save seed are the biennials. Biennial crops grow vegetation the first year and produce seed in their second year. This means that you will have to make sure that you leave some plants over the winter in your garden and leave them there in the spring until they set seed. Plants that are not winter hardy in the north may have to be lifted, stored, and replanted in the spring. Because these are also cross-pollinated crops you may also have to be mindful of other plants of the same species that are blooming at the same time. Seed from some of these crops are viable for 2-5 years so you can alternate saving crops year to year. Biennial crops include beets, chard, parsnips, carrots, celery, onion, turnips, rutabaga, cabbage, Brussels sprouts, cauliflower, and kale. In the Seed Sharing Library the drawers containing Advanced Crops will have a pink dot.
Please note: Cross pollinating different cultivars on purpose or gathering seed of undetermined parentage is fine if you are experimenting for your own seed supply, but please refrain from contributing seeds to the Seed Sharing Library unless you have taken the above precautions.