#and somehow I don't see urban and suburban gardeners having that much space to devote to kale

[turtlesandfrogs]

Are Heirloom varieties inbred?

I got this question recently on one of the gardening forums I frequent, and I thought it was a really interesting question, so I thought I'd post it, and my response here.

"... I wanted to ask you specifically, what do you think of "heirloom" plants? I was excited to collect a few different varieties through plant swaps and seed organizations. However, I've become slightly concerned when I realized that heirloom plants are, by default, highly inbred. Should this be considered a problem in plants? If I grow them, should I keep them separate or allow them to cross-pollinate?"

And my response, expanded a bit:

Well, here's the thing, they shouldn't be highly inbred, which is one reason to get them from a reputable source. When you're saving seeds from heirlooms or open pollinated varieties, you should be selecting from enough plants to maintain a good amount of genetic diversity. I think this is sometimes overlooked when people first start saving seeds, but you should be planting and growing out enough plants that you can select for the characteristics that matter most to you, and among that population still have more than enough to carry on genetic diversity. Of course sometimes bottlenecks will happen, and more than one variety has been saved from extinction by a singular plant, but that's far from ideal.

That genetic diversity is why heirloom and open pollinated plants have more variability than hybrid plants, and it's part of why they are adaptable- they have enough variability in their genetics that each strain is going to be slightly different because of the conditions in which they were grown. Combine that with plant's awesome use of inheritable epigenetic, and if you save seeds, plants will adapt incredibly quickly to your own gardening conditions.

Further, when you're selecting plants to save seed from, you should be selecting for health and vigor along with other variety-specific traits. Keep in mind that each heirloom or open pollinated variety is under going evolution- your job as a seed saver is to select for plants that meet the description of the variety while being as healthy (and productive) as possible.

If you cross heirloom varieties, you are just making your own hybridization, but since the varieties you're crossing aren't highly inbred (unlike how they do it commercially to make hybrids), you're going to have a wild mix of outcomes- which isn't necessarily a bad thing! That's how new varieties are created. You cross two or more types that have traits that you like, and try to select plants that have the best combination of traits, and you repeat that for several generations. You could make your own landrace variety by allowing all your heirloom/op varieties to interbreed, and then selecting the best plants down over the generations.

And of course, some plants are inbreeders and don't really suffer from inbreeding depression the way corn- or the Spanish royal family-might. Peas are a good example of what plant breeders call an inbreeder. They pollinate themselves, and you have to interfere if you want to get a pea plant to pollinate with another one. You could save seed from 5 to 10 plants every year for generations, and you wouldn't see much inbreeding depression. If you tried that with corn, well, you'd see the (negative) results very quickly.

A great book on this topic is 'Breeding your own Vegetable Varieties' by Carole Deppe, highly recommend checking it out. Also, here's a link to a seed saving chart with population sizes for different varieties: https://www.communityseednetwork.org/wp-content/uploads/2021/04/SS-Seed-Saving-Chart-English.pdf And this is another very informative pdf: https://seedalliance.org/wp-content/uploads/2010/04/seed_saving_guide.pdf