As most people know, mushrooms love dark places. You can find them growing in the dim recesses of forests or at the foot of old trees. But is that where we get most of the mushrooms that end up in our hearty risottos and juicy portabella sandwiches?

You would be forgiven for thinking that's the case, given the growing popularity of mushroom hunting. But the truth is, most of the mushrooms we eat in the U.S. come not from foragers scouring the forest floor but from farms — indoor farms, to be exact.

Where, you might ask, is the fun in that?

While mushroom farming may not be as thrilling as fungi hunting, a 2014 video from the Web series "?" shows that it's still an interesting sight. In it, journalist Nicole Cotroneo Jolly takes her viewers to Phillips Mushroom Farm, one of the largest producers of button and exotic mushrooms found in Chester County, Pa.

The U.S. produces 900 million pounds of the savory fungi a year, including both button and exotic species. And it's a billion-dollar industry. Roughly half of the mushrooms produced in this country come from Chester County, aptly dubbed the "mushroom capital of America."

For that, thank the Quakers, who started growing mushrooms under their carnation beds in the late 1800s. As The Salt's Dan Charles has reported, the idea then took root among Italian immigrants hired to do physical labor. Soon, Italian families in the area were starting their own mushroom farms and passing them down from generation to generation. Fast forward to today and there are hundreds of mushroom farmers in the U.S.

All in all, 98 percent of the mushrooms produced in the U.S. are your typical white and brown button mushrooms. And they grow in dark, humid and cramped "mushroom houses" — just the way the fungi like it.

Stacked inside the houses of are row after row of mushrooms nestled in compost beds. The mushrooms start out as spores that get mixed in with the soil. In two weeks, the meaty part will grow above ground, doubling in size every 24 hours, general manager Jim Angelucci tells Jolly. Once they're mature, the harvester gives each one a gentle push and a slight twist before pulling the entire thing out.

What about the "exotic" mushrooms that have been making their way into fancy dishes at restaurants? You'd think they come from the wild, but those likely came from a farm, too, says Kathleen Preis, marketing manager at the , an industry group. While the Mushroom Council doesn't track sales of wild-picked mushrooms, Preis tells The Salt that only a small amount of the exotic kinds we eat come from professional foragers.

You see, species like the king trumpet, shiitake and oyster mushroom make up the other 2 percent of U.S.-produced edible fungi — about 18 million pounds' worth each year. Since the 1980s, when these mushrooms were first introduced into the American market, production has ramped up seven-fold to meet growing demand, according to the U.S. Department of Agriculture.

Unlike button mushrooms, however, the exotic ones prefer old trees and rotting logs, according to the video.Turns out, farmers have figured out a way to mass-produce that as well. They use synthetic logs, made of sawdust and other plant materials, Jolly tells viewers. To keep them moist, the logs are bundled together and given a good dunk in water.

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