Why Do Grocery Stores Cover Potatoes at Night?

If you’ve ever walked into a grocery store late at night, you may have spotted a mysterious blanket draped over the potatoes. It turns out that there’s a perfectly logical explanation as to why grocery stores take the time to cover their spuds in the evening.

Some foods, like tomatoes, are quicker to ripen with warm temperatures and fresh air. Potatoes are the exact opposite. They like it cold and dark—and they especially don’t like to sit under the harsh glow of fluorescent lighting. 

When exposed to too much light, especially for long periods, potatoes start to turn green. That green color is caused by the production of chlorophyll (which is technically harmless). But it’s also a sign that something less friendly might be brewing.

Can you eat green potatoes?

Solanine is a natural toxin that potatoes produce when they get stressed out by light or damage. It’s a defense mechanism that, in small amounts, is not a big deal. If a potato turns very green, however, that’s a signal that solanine levels may be climbing to potentially dangerous levels. According to food safety experts at Michigan State University, you’d have to eat a lot of green potatoes to get seriously sick. But that doesn’t mean it’s a good idea. 

Solanine (along with its sidekick, chaconine) can cause symptoms like nausea, vomiting, headaches, or digestive issues. If your potato has a small green patch, you can usually cut it away and cook the rest. But if the whole thing is green, soft, or sprouting, you should toss it.

Covering potatoes at night is a simple way for grocery stores to prevent greening in the first place. It’s a cheap fix that keeps the produce looking (and tasting) fresher for longer—and saves stores from having to trash entire bins of mildly toxic starch.

If you’re storing potatoes at home, there’s no need to break out the moving blankets. Just keep them in a dark, cool place like a pantry, cabinet, or even a shoe box. 

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