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Question: I saved the seeds from my 16-ounce heirloom tomatoes, trying to replicate their size, but my biggest one was only 8 ounces. I don’t remember the variety of heirloom, since I received them long ago. I’ve noticed that when I save the seeds, there are only about 20 seeds or so in them, and most of the seeds are in the end of the tomato. In order to propagate an heirloom plant, how many seeds from how many plants do you need to save? — Verdie Harper

Oscar H. Will III: A single tomato might be fine for next year, but mixing it with five different plants would be better. And if you want to preserve an heirloom, you should plant them at least 50 feet away from other tomato cultivars. To maintain the cultivar over time, more is always better, but 10 plants — and several fruit per plant — would likely cover it. You’re lucky it isn’t corn! You’d want about 200 ears from 50 plants to preserve the diversity of corn cultivars.

Plenty of new cultivars have gone through a bottleneck of sorts with regard to lost genetic diversity because only a few seeds were saved, but these tend to be less resilient to wide geographic adaptation.

People often confuse true breeding — a specific physical trait passed down through generations —with a lack of genetic diversity. Though heterosis, a display of qualities superior to previous generations, is somewhat reduced in the genes that control looks and fruit characteristics, there is incredible diversity in all of the rest of the genetics. That’s why well-preserved cultivars have a better chance of surviving climate change than poorly preserved ones.

For more information on saving seeds from a wide variety of heirlooms, take a look at the Seed Savers Exchange website. They offer a well of great information on saving seeds, seed starting, and isolating plants for heirloom preservation.

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Hank is the Editorial Director at Ogden Publications.