26/03/2022
I find that there’s not a lot of talk about how large a population you need when people do talk about seed saving. I think it’s a lot bigger than most people expect, especially for out-crossers like broccoli and corn. On top of that, if you want to be growing something different than your neighbors (or say, want to save broccoli seed when a lot of people let kale go to seed around you), you need to consider isolation distances. Let’s look at population size first.
Did you know that if you want to maintain the health and vigor of a particular kale variety, you need to grow out 20 to 50 plants? For long term genetic preservation, you need more than 80. For most suburban gardeners, that’s a lot! Not all plants need this many- but a lot of plants that are pollenated by the wind or insects do. On the other end, we have self-pollinating species, like lettuce, peas, and beans. For them, you only need to save seed from 5 to 10 plants to maintain a variety- which is much more manageable in a suburban garden.
Then, you have to consider isolation distance- and whether it’s even possible where you live. Isolation distance is basically how far apart two varieties need to be to prevent cross pollination. For example, if you had two different varieties of broccoli that you wanted to save seed from, they’d need to be separated by 800 feet to half a mile- which is pretty difficult in the suburbs. Especially once you consider that if someone else’s broccoli, cabbage, Brussels sprouts, or non-Siberian kale is flowering at the same time as your crop, there will be cross pollination if they’re within that distance (Siberian kale is actually a different species- same genus though).
Now, I want to save some Siberian kale seed, and I know that someone, who is less than half a mile from me always has a patch of Red Russian (a type of Siberian kale) that goes to seed. This has an upside, and a downside. The upside is a larger population and more genetic diversity- which, since kale is an outcrossed, should yield more vigorous plants. The downside is that I don’t know what, if any, intentional selection is going on with that patch of kale. I’ll be selecting for winter hardiness, tastiness, vigor, and pest resistance, but maybe they’re selecting for the ability to grow in crowded conditions, or being able to survive in a chicken run for 3 months. If I were growing a fussier plant, like Brussels sprouts, this might be enough to dissuade me from saving seeds, but since kale is such a hardy, unrefined plant anyway, I don’t think it will be a problem.
Where it becomes more of an issue is with pumpkins and squash. And that’s because there’s three (or four) different species that all have varieties called ‘pumpkin’ or ‘squash’. Did you know that zucchini and Delicata are the same species as the New England Sugar Pie pumpkin? Or that Kabocha, Banana, and Hubbard are all the same species? Fortunately, though they have a large isolation distance (because bumble bees love them), their population size is small (5 to 10 to maintain a variety), and it’s easy to tape close blossoms before they open and then hand pollinate.
If I were growing corn, it would be again, another consideration, because they are a) wind pollenated, b) need a very big population size, and c) if sweet corn pollenates popcorn, there'll be some issues. I'll probably keep buying corn seed.
I’m not trying to scare you off of saving your own seeds, I just want you to think about what you’ll need to do to maintain varieties, and have the information you need to know. Here are a few resources that will help you do that:
https://www.communityseednetwork.org/resources/
Click to access SS-Seed-Saving-Chart-English.pdf
https://www.llojibwe.org/drm/greenteam/seedsaving.html
I also think people who maintain or develop new varieties are awesome, and here's some of my favorite seed sources:
Uprising Organics
Fedco Seeds
Territorial
West Coast Seeds
Johnny's
Leech Lake Division of Resource Management.
