Seed saving calendar: when to harvest, how to dry, how to store

Pick a crop. Get the exact maturity signs to look for, the drying technique that won't kill the embryo, and the storage temperature that gives the longest viability. Data compiled from Seed Savers Exchange, Cornell Garden-Based Learning, and the Penn State Master Gardener Seed Saving Manual.

The two-rule heuristic

Rule 1: dry seeds slowly at room temperature. Heat above 95°F kills the embryo. Most seeds need 1-2 weeks of air drying before storage.

Rule 2: store dry seeds in airtight containers at consistent cool temperatures. The sum of temperature (°F) + humidity (%) should not exceed 100. A refrigerator at 40°F at 30% humidity (a sealed jar with silica gel) gives the longest viability — 5-10x longer than room temperature storage.

Per Seed Savers Exchange, properly stored seeds of most vegetables remain viable 3-5 years, with cool-season crops (lettuce, peas) lasting longer than warm-season crops (corn, peppers).

What's hard, what's easy

Easiest (selfing annuals): tomatoes, beans, peas, lettuce, peppers. They pollinate themselves; you can save seeds from a single plant without worrying about cross-pollination.

Medium (insect-pollinated annuals): brassicas (broccoli, cabbage), squash, melons, cucumbers. You need isolation distance or hand-pollination to prevent cross-pollination from other varieties.

Hardest (biennials): carrots, beets, onions, parsley. They produce seed in their second year, requiring overwintering. In zones below 7, you need to dig and store roots, then replant in spring.