Seed Saving Isolation Distances Chart for Home Gardens
How far apart to grow varieties for pure seed: 10 to 100 ft for beans, 25 to 100 ft for tomatoes, 1,600 ft for cucumbers, and 1/2 mile or more for squash,...
Published by ThriveThyme
seed saving isolation distance chart
Seed Saving Isolation Distances
Isolation distance is how far apart two varieties of the same crop need to be so they do not cross. Self-pollinating crops need only a short gap. Crops moved by bees or wind need much more.
These are home garden figures. They stop most crossing, not all of it. Neighbors' gardens count too.
Check your own crops on the Seed Saving Desk.
Chart
| Crop | Pollinated by | Distance for pure seed |
|---|---|---|
| Bean | Self | 10 to 100 ft |
| Tomato | Self | 25 to 100 ft |
| Pea | Self | 50 ft |
| Lettuce | Self | 50 ft |
| Eggplant | Self | 150 ft |
| Pepper | Self and insects | 160 to 500 ft |
| Radish | Insects | 1,500 ft |
| Carrot | Insects | 1,500 ft |
| Onion and leek | Insects | 1,500 ft |
| Cucumber | Insects | 1,500 to 1,600 ft |
| Squash and pumpkin | Insects | 1/2 to 1 mile, same species |
| Melon and watermelon | Insects | 1/2 to 1 mile |
| Kale, cabbage, broccoli | Insects | 1/2 mile |
| Beet and Swiss chard | Wind | 1/2 mile |
| Spinach | Wind | 1/2 mile |
| Sweet corn | Wind | 1/2 mile |
Figures from the UC Master Gardener seed saving chart, UGA Extension (bean 10 ft, pepper 160 ft, cucumber 1,600 ft), and SDSU Extension (squash, melons).
Notes That Matter
- Potato-leaf and heirloom tomatoes need the far end of the tomato range.
- Hot peppers cross more readily than sweet peppers.
- Squash cross only within the same species. See how to save pumpkin and squash seeds.
- Beets cross with Swiss chard. Kale, cabbage, broccoli, collards, and cauliflower all cross with each other.
- Carrots cross with wild Queen Anne's lace.
- Popcorn or field corn can cross with sweet corn and ruin the flavor.
No Room? Other Ways to Keep Seed Pure
- Grow one variety of each crop per year. Save a different one next year.
- Stagger planting so two varieties do not flower at the same time.
- Cover plants with fine netting, or tape flowers shut and hand-pollinate. This works well for squash.
- Bag the flowers you want seed from before they open.
Next Steps
- Find out if your seed is worth saving on the Seed Saving Desk.
- Learn how to save bean and pea seeds, the easiest place to start.
Sources: UC Master Gardeners, Saving Seeds chart. UGA Extension Circular 1242, Seed Saving in Georgia Gardens. SDSU Extension, Saving Seed of Pumpkins, Squash, Cucumbers, Melons and Gourds. University of Minnesota Extension, Saving vegetable seeds.