Seed Saving Isolation Distance Calculator
Find the recommended isolation distance between varieties of the same crop, so the seeds you save grow true to type next year.
How this calculator works
Self-pollinating crops like tomatoes and beans rarely cross even at short distances, since pollination usually happens before the flower even opens. Insect-pollinated crops need much more room, since bees regularly forage hundreds of feet. Wind-pollinated crops like corn and beets need the most distance of all — pollen can travel remarkably far on the breeze.
Where these numbers come from
- Primary isolation distance table: University of Illinois Extension, "How to Save Seeds" (2021)
- Cross-referenced against University of Maryland Extension seed-saving guidance and UC Agriculture and Natural Resources seed-saving tables
Real-world published guidance varies meaningfully between sources for several crops — that's not an error, it reflects genuinely different risk tolerances between home gardeners and commercial seed producers.
Frequently asked questions
Why do I need distance between varieties at all?
Many garden crops are cross-pollinated by wind or insects, and pollen from a different variety of the same species landing on your plants can produce seed that doesn't grow true to the parent plant next season — isolation distance keeps that cross-pollination from happening.
Why does required distance vary so much by crop?
It depends on how the crop is pollinated — wind-pollinated crops and insect-pollinated crops travel pollen very different distances, and some crops self-pollinate reliably enough to need very little isolation at all, so a single universal distance wouldn't make sense across different crops.
Does a physical barrier like a fence reduce the needed distance?
Some barriers and timing tricks (like staggered bloom times) can help reduce cross-pollination risk, but they're not a substitute for isolation distance in most seed-saving guidance — treat them as a supplement, not a replacement.
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