A dialectic1.
Q: I didn’t eat my potatoes fast enough, they grew sprouts! I’m going to plant them.
A: Don’t do that.
Q: Why? They’re a fine variety if they’re what the grocery store has, aren’t they?
A: Yes, the genetics are good. But it’s not a seed potato.
Q: Why do I need a seed potato, what’s the difference?
A: Seed potatoes and commercial potatoes are the same genetics, the same plants. But seed potatoes are specifically grown in extremely cold regions (think north of Edmonton), where brutal winters kill most of the pathogens in the soil.
Soil is full of stuff, including fungal spores and bacteria. Think of a sourdough culture—microbes always keep upping their populations when they have suitable food available and when they’re not killed by harsh environments. Some fungal spores survive in the soils where seed potatoes are grown—but far fewer.
So the life cycle of a potato is
grown for seed north of Edmonton (or tippy top Maine, or somewhere equivalently harsh)
shipped to Idaho, cut into pieces (potatoes are grown as clones), allowed to sprout, planted, and grown for grocery store
picked up fungal spores in the Idaho soil
in the store → in your home → in your stew
but if you skip the stew step and you plant it, in YOUR soil, where it has more fungal contact again
One cycle of this (whether it’s Alberta to Idaho; or Maine to your garden) winds up being okay. Fungus won’t overtake your crop.2 But if you plant it again after it’s already grown a whole cycle in a non-tundra-adjacent soil, you’re starting with a critical mass of disease.
Q: Dang.
A: This is also why you need to do crop rotations (or, you put potatoes in one place in your garden this year, and then elsewhere next year). Best practice (if you are a commercial potato farmer) is 4 years of non-nightshade in between each nightshade (2022 potato, 2023 corn, 2024 soybean, 2025 corn, 2026 soybean, 2027 potato again).
This works because the potato funguses don't proliferate on grasses or legumes.
Q: Can’t they just use pesticides?
A: I mean, yes, but that’s only part of the solution—I’m just saying “funguses” but there are scores of different potato diseases (some fungal, some bacterial) and different pesticides attack different diseases. Plus, fungicides are expensive, and growers’ groups coordinate to figure out use patterns that will not result in resistant strains, so growers have restrictions on which products/what rates/how many times per year they can be used. So pesticides are part of the solution, but they can’t solve the problem without a solid foundation of crop rotation, and growing the seed potatoes in the deep north.
Q: huh, interesting. How come people could grow potatoes in the past, then?
A: They had lower-yielding but less susceptible varieties of potatoes. And of course they used crop rotation technology—we learned it from them.
Works cited: conversations with potato growers and seed potato growers, conversations with plant pathologists, potato experience in my own garden. But if you want a site for more info, I glanced at this and it both looked accurate, and provided this nice propaganda graphic: https://www.albertapotatoes.ca/alberta-seed-potatoes
Surely I’ll push a real piece through the draft stage and publish some thoughts instead of just fungal trivia one of these days… but I just heard from a friend whose garden spud crop had failed. I share this info a lot and nobody’s heard of it before, so, here’s the atomic citation essay!
Though you might find some, and if you do you should remove the diseased plant(s), seal them tightly in double layered garbage bags, and landfill them. Do not compost.