Seed saving basics: which seeds to save, isolation, harvesting and drying

Seeds & saving · Published 2026-10-24

A wicker basket full of speckled cream and maroon dry bean seeds — 'Early Mohawk', an heirloom dwarf bean, saved as dry seed. Photo: Bicanski, via Wikimedia Commons, CC0.

Every seed catalog is built on seed someone saved. Saving your own lets you keep varieties you love, adapt them slowly to your garden, and share them with neighbours. It is easier than it sounds, if you start with the right crops and understand one thing: how the plants are pollinated.

Which varieties to save

Save seed from open-pollinated varieties, including heirlooms. They produce seed that grows into plants like the parent, as long as they have not been crossed with another variety. F1 hybrids are the result of a deliberate cross between two parent lines; University of Illinois Extension explains that seed saved from hybrids usually does not look like the parent plant, which makes hybrids poor choices for seed saving. Catalogs mark hybrids as "F1" or "hybrid": see how to read a seed catalog.

Some varieties are protected by plant variety protection certificates or patents, which limit what you may do with their seed, particularly selling it. Catalogs usually mark protected varieties; check before sharing or selling seed you have saved.

The easiest crops to start with

Illinois Extension lists peas, beans, lettuce and tomatoes as easy crops for beginners. They are annual and largely self-pollinating, so they need little isolation and you only need a few plants to get good seed.

Crop	Pollination	Suggested isolation for seed saving	Harvest
Pea	Self	10–20 ft	Dry pods on the plant
Common bean	Self or insect	10–20 ft	Dry pods on the plant
Lettuce	Self	10–20 ft	Dry, fluffy seed heads
Tomato	Self or insect	10–50 ft	Wet seed from ripe fruit, fermented
Pepper	Self or insect	300–1,600 ft	Seed from fully ripe fruit
Squash, pumpkin, cucumber, melon	Insect	800 ft to ½ mile	Seed from fully mature fruit
Corn, spinach, beet	Wind	800 ft to 1 mile	Dry seed; hard to isolate in gardens

Distances are those in the Illinois Extension guide, drawn from Seed Savers Exchange recommendations; for most crops they are ranges, and the right distance depends on the variety and on what your neighbours grow.

Understanding isolation

Different species do not cross with each other: a cucumber will not cross with a squash, despite the folk belief. But different varieties of the same species can: two kinds of summer squash, or a summer squash and a pumpkin of the same species, will cross freely, and the next generation's plants will be a mix. The fruit you eat this year is not affected, only the seed inside it. There are three ways to isolate:

Distance: grow only one variety of a crop, or keep varieties as far apart as the crop needs.
Time: stagger sowings so varieties do not flower at the same time.
Barriers: cover flowers or whole plants with bags or row covers, and hand-pollinate with a small brush.

Choosing plants to save from

Save from several healthy, typical plants rather than one, to keep genetic diversity, especially for cross-pollinated crops.
Choose plants with the traits you want: flavour, earliness, disease resistance, and for leafy crops, slowness to bolt.
Grow enough plants for both eating and seed.

Harvesting: dry and wet seed

Dry seed

Beans, peas, lettuce, onions, carrots, corn, many herbs and flowers. Let seeds mature and dry on the plant as far as possible. Illinois Extension advises cutting seed heads of small, light seeds just before they are fully dry to prevent losses, then finishing the drying on a screen in a single layer in a cool, ventilated place, or in paper bags. Shell, sieve or winnow away the chaff.

Wet seed

Tomatoes, cucumbers, melons and other fleshy fruits. Let fruit ripen fully, past the eating stage for cucumbers and squash. For tomatoes, Illinois Extension recommends fermentation:

Scoop seeds and gel into a jar with a little water.
Leave for two to four days, stirring daily; a film of mould on top is normal.
Viable seed sinks; pour off the floating pulp and poor seed.
Rinse the good seed and spread it thinly on a paper towel or fine screen to dry completely.

Drying, labelling and storage

Dry seed thoroughly before storing: damp seed moulds or loses viability quickly.
Store in paper envelopes; for long-term storage, Illinois Extension suggests paper envelopes inside a glass jar, which is pest-proof.
Label each envelope with crop, variety, date and any notes such as "isolated" or "possible cross".
Keep in a cool, dry, dark place. See how long seeds last for storage and germination testing.

Sharing seed

Seed swaps, library seed collections and seed-saving organisations are a way to share varieties and find new ones. When sharing, label honestly: say whether the seed might be crossed, and include growing notes. If you send seed by mail to other states or countries, remember that plant health rules apply; see plants and seeds across borders.

Common beginner mistakes

Saving seed from hybrids and expecting the same plant next year.
Harvesting fruit too early: seed must be mature, which for squash and cucumbers means well past eating ripeness.
Storing seed before it is completely dry, which leads to mould.
Saving from a single plant, which narrows the variety over time.
Forgetting to label, and losing track of which seed is which.

Start with peas, beans, lettuce and tomatoes, and label everything.

Sources

University of Illinois Extension (2021), How to save seeds, including the isolation distance chart from Seed Savers Exchange.
University of Illinois Extension, Open-pollinated vs. hybrid: an important distinction when saving seeds.
Seed Savers Exchange, Isolation distances.