Plan Your Seed Garden Before You Plant

Pick the crops you are growing and find out which seeds you can safely save and swap, which need isolation distances, and which should be bought fresh each season. No more mystery squash.

Your Seed Saving Report

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No crops selected yet.

Click crop buttons on the left (or try a preset above) to build your garden plan and see seed saving compatibility results here.

Seed Saving Reference

The science behind why some seeds grow true and others turn into surprises.

How Pollination Type Affects Seed Saving

Self-pollinating crops like tomatoes, peppers, peas, and beans fertilize themselves before the flower even opens. They are the easiest to save. Different varieties can grow close together and still produce true seed.

Cross-pollinating crops rely on wind or insects to move pollen between plants. Corn, squash, carrots, and most brassicas fall here. If two varieties of the same species are blooming nearby, the pollen mixes and the seeds carry traits from both parents.

Some crops do both. Peppers and eggplants mostly self-pollinate, but insects can carry pollen between varieties. At 10-20 feet apart, the risk is low. At a seed swap where many varieties grow together, it is not.

Open-Pollinated vs. Hybrid vs. GMO

Open-pollinated (OP) varieties breed true when isolated from other varieties of the same species. Most heirlooms are OP. These are the best candidates for seed saving.

Hybrid (F1) varieties are the result of a controlled cross between two parent lines. The first generation is uniform, but the second generation (the seeds you would save) splits into a wide range of traits. You can save them, but expect surprises.

GMO seeds are rarely sold to home gardeners, but some field corn and soybean varieties are genetically modified. These are patented and saving them may violate the purchase agreement. For home gardeners, the practical advice is simple: if the packet says F1 or hybrid, do not save seed expecting the same plant.

Isolation Distance Chart

CropMin Distance (casual)Min Distance (strict)
Tomato10-20 ft50 ft
Pepper50 ft200 ft
Bean / Pea10-20 ft50 ft
Lettuce10-20 ft50 ft
Corn250 ft1/2 mile
Cucumber1/4 mile1/2 mile
Squash (same species)1/4 mile1/2 mile
Carrot1/2 mile1 mile
Beet / Chard1/2 mile1 mile
Brassica family1/2 mile1 mile
Dill / Cilantro1/2 mile1 mile
Sunflower1/2 mile1 mile

Casual distance works for home gardeners who accept a small amount of crossing. Strict distance is for seed swaps, seed libraries, and anyone sharing seed with others. Physical barriers like hedges, buildings, and tall crops can reduce effective distance.

Common Mistakes That Ruin Seed Harvests

  • Planting two zucchini varieties side by side. Both are Cucurbita pepo. They will cross. The saved seeds may produce bitter, odd-shaped fruit next year.
  • Saving seeds from hybrid tomatoes. The plants look great, but the offspring will be unpredictable. Save from heirloom varieties instead.
  • Not isolating carrots and Queen Anne's lace. Wild carrot (the white roadside flower) will cross with your garden carrots and produce bitter, white roots.
  • Harvesting squash seeds too early. Seeds from immature fruit are often not viable. Wait until the squash is fully ripe (hard rind) before saving seeds.
  • Storing seeds in a warm, humid place. Heat and moisture kill seed viability. Store in a cool, dry location in labeled paper envelopes with a silica gel packet.
  • Forgetting that beets and chard are the same species. Beta vulgaris includes beets, chard, and sugar beets. If both are blooming, they will cross-pollinate.
  • Assuming all pumpkins are the same species. Jack-o-lantern pumpkins are Cucurbita pepo, but some large carving pumpkins are Cucurbita maxima. They will not cross with each other, but they will cross with other varieties in their own species.

Seed Saving Calendar

A month-by-month guide for when to harvest, process, and store seeds from common garden crops. Print this page and hang it in your potting shed.

January - February

  • Order seeds for the coming season. Review last year's saved seeds and test germination rates.
  • Check stored seeds. Discard any that show mold or insect damage.
  • Plan your garden layout with isolation distances in mind.
  • Start leeks and onions indoors if you plan to overwinter them for seed (biennial).

March - April

  • Plant peas, lettuce, and beans. These self-pollinators are safe to save with minimal isolation.
  • Transplant overwintered biennial roots (carrots, beets, onions) back outside to flower and set seed.
  • Mark plants you intend to save seed from. Choose the healthiest, most typical specimens.

May - June

  • Plant corn in blocks (not single rows) for better pollination and fuller ears.
  • Hand-pollinate squash if you are growing multiple varieties and want pure seed. Tape female and male flowers shut at night, then hand-transfer pollen in the morning.
  • Let lettuce and bolting herbs (dill, cilantro) flower if you want seed from them.
  • Harvest pea and bean seeds when pods are dry and rattle.

July - August

  • Harvest tomato seeds from fully ripe fruit. Ferment seeds in water for 2-3 days to remove the gel coating.
  • Collect pepper seeds from fully ripe (usually red or yellow) fruit. Dry on a paper towel.
  • Let lettuce, basil, and cilantro go to seed. Collect when seed heads turn brown.
  • Mark and save the best bean and pea plants. Let them dry on the vine.

September - October

  • Harvest squash and pumpkin seeds from fully mature fruit. Rinse and dry thoroughly.
  • Collect sunflower seeds when the back of the flower head turns brown.
  • Dig biennial roots (carrots, beets) you want to overwinter for seed. Store in damp sand in a cool root cellar.
  • Finish drying all seed harvests. Label everything with crop, variety, and date.

November - December

  • Store dried seeds in paper envelopes inside an airtight container. Add silica gel packets.
  • Keep seeds in a cool, dark place. A refrigerator works well for long-term storage.
  • Make a list of which seeds you need to buy fresh next year (hybrids and high-cross-risk crops).
  • Start planning next year's garden. Use this checker to plan isolation distances.

How This Works

1

Pick Your Crops

Click the crop buttons to add them to your garden plan. Use the presets for common garden types. You can mix and match freely.

2

Read Your Report

The results panel updates as you go. Green means safe to save. Yellow means you need isolation. Red means buy fresh. Warnings flag specific cross-pollination risks.

3

Plan and Share

Copy your report, print it, or share it with a link. Use the reference section below to understand why certain crops need special handling.

Things to Keep in Mind

  • Isolation distances are conservative guidelines for home gardens. Your actual risk depends on insect activity, wind, and neighboring gardens.
  • Physical barriers (fences, buildings, tall crops) can reduce effective isolation distance.
  • Hand-pollination with flower bagging is the most reliable method for squash, corn, and other high-risk crops.
  • This tool covers common garden vegetables and flowers. Rare or regional varieties may behave differently.
  • Seeds saved from hybrid (F1) varieties will not breed true. Save from open-pollinated or heirloom varieties for reliable results.