In many ways, planning a seed saving garden is the same as planning any garden. You want the plants to receive their nutritional, water, light and pollination requirements, and to reach the end of their life cycles as healthily and productively as possible.
For a seed saving garden, however, there are a few additional considerations:
- Plants grown for seed often need more time in the garden for the seed to ripen fully
- Certain isolation distances are required from other plants of the same species
- Minimum population sizes are needed to protect genetic diversity
Time in the Garden
Consider lettuce. Normally, you harvest lettuce anywhere from 6-12 wks after sowing. But to grow lettuce seed, you must allow the plants to bolt, developing tall stalks and flowers. The seed isn’t ready to harvest for another 4-6 wks after you would have eaten the lettuce. Cucumbers, zucchini and beans are examples of other annuals that require additional garden time for the seeds to reach full maturity. Additionally, some vegetables are biennials, meaning they won’t produce seed until their second season of growth.
Crops in the same species can cross-pollinate with each other. When this happens, the saved seed will not grow a plant of the same variety as its parent. This makes it important to know the species of the plants you want to keep seed from. In many cases it is quite simple – tomato varieties are all the same species, as are lettuces and peas. However, would you have known that zucchini could cross-pollinate with acorn squash? Broccoli with curly kale? Turnips with mustard greens? Beets with swiss chard?
Crops and varieties of the same species require isolation from each other to prevent unwanted cross-pollination. There are essentially two categories of species: those that self-pollinate, and those that cross-pollinate. The former require fairly small isolation distances (e.g beans 3m), whereas the latter require much larger ones (e.g. squash 400m). You may need to consult your neighbours in planning for your seed saving garden! Seed saved for commercial purposes requires even larger distances than those considered sufficient for personal seed saving. Fortunately, there are ways to get around large isolations distances if you’re willing to hand-pollinate, cage, or stagger flowering periods.
Minimum population sizes
Just like human communities can become inbred without maintaining a certain breadth of genetic material, so too can plant varieties. Minimum populations needed to retain healthy genetic diversity differ from species to species, but usually fall with a range of 6-20 cross-pollinating plants. This may mean you need to plan for more space in your garden for a particular crop than you would if you were only growing it to eat.
It’s worth a try!
Although this may sound a bit daunting, incorporating 1 or 2 seed crops into your garden planning is not that difficult! Beans, peas and tomatoes are great for beginners. If you’re ready for the next challenge, consider lettuce or radishes. Eventually you may want to experiment with biennials! For more detailed information on seed saving requirements, our How to Save Your Own Seeds book includes family-specific seed saving information, handy reference charts, some botany basics, and lots of tips on harvesting, cleaning and storing seeds.
This article was reprinted with permission from the April issue of Seeds of Diversity Canada’s e-bulletin
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