Gregg Hutson’s shady backyard would be a wet blanket for most gardeners. Not for Mr. Hutson, who grows mushrooms at his home in Takoma Park, Md. “It’s pretty spongy,” says the 43-year old advertising agency copywriter, stepping around some chanterelles. “Great mushroom-growing conditions.”

Mushrooms—the ones intended for culinary purposes—are in. More than 400 food products featuring mushrooms were introduced in 2017, up 22% from a year earlier, according to Innova Market Insights. The rise of the mushroom comes as more consumers seek so-called functional foods that promise to do more for the body than just provide nutrition. Whole Foods Market has called “functional mushrooms” one of this year’s top food trends, and labels on teas and other elixirs increasingly hail mushrooms as “adaptogens”—ingredients makers claim help the body fight stress.

And with prices that can run north of $10 a pound for certain specialty mushrooms, many people are figuring out how to grow their own.

In Catonsville, Md., 40-year old biologist Peter Sykora this spring began collecting mushroom spores from oyster, shiitake and morel mushrooms he bought at farmer’s markets. Spreading out the mushrooms on aluminum foil overnight, he was able to collect the powdery deposits. He first put the spores in bits of wet cardboard to encourage initial growth called mycelium. About two weeks ago, he placed the mycelium in buckets of woodchips and straw outdoors to encourage further growth. In the coming months, he will transfer it all to a 4-by-4-foot plot in the shade of his backyard, filled with layers of logs and woodchips. The mycelium eventually produces mushrooms.

Dr. Sykora says he was sometimes taken aback at the price of unusual mushrooms and wanted to try growing his own. The exceptionally wet spring, optimal for mushrooms, has been a boon. “It inspired me,” he says.