Forest Mushrooms feeds growing need for fungi

Kevin Doyle grows oysters
Rachel Hutton

With his whitish beard and slight build, Kevin Doyle bears some resemblance to Rumpelstiltskin—that is, if the German elf wore Wranglers and lived on a former hog farm in St. Joseph, Minnesota. When Doyle first launched Forest Mushrooms back in the mid-1980s, he was, in a way, spinning straw into gold: He'd process a bedding-like mix of agricultural materials, inoculate the substrate with fungus, and a few weeks later, sell his specialty mushrooms to Twin Cities restaurants and grocery stores.

In addition to growing oysters and shiitakes, Forest Mushroom buys bulk mushrooms from all over the world—cultivated portobella, crimini, and enoki mushrooms, for starters, as well as wild-harvested chanterelles, lobster mushrooms, and porcini, among others—and repackages them for food service or retail sale. A few weeks ago, I visited Forest Mushrooms, which is the only commercial mushroom cultivator in the state, just as the season's first morels had arrived from the Pacific Northwest. Several employees were weighing and repackaging the prized mushrooms—they sell for roughly $40 a pound—into the small wooden tills. In addition to supplying fresh mushrooms, Forest also imports dried mushrooms from China and packs them in small plastic bags for sale at Whole Foods stores in the Midwest and Mid-Atlantic.

Doyle, who has a natural-sciences background, was doing biofuel research for the University of Minnesota when he developed an interest in mycology, the study of fungi. At the time, most supermarkets carried only white buttons, or as Doyle calls them, the "Wonder Bread mushroom." Portabella mushrooms—now a menu mainstay even at Applebee's—were considered exotic.

In the past 20 years, the specialty mushroom market has really—forgive the pun—mushroomed. At first Doyle sold his cultivated mushrooms to customers around the United States, but today local demand is such that he sells almost all he can grow within the state. Doyle estimates that when he first got into the business, Twin Cities restaurants and grocery stores bought about 300 pounds of mushrooms a week; today he guesses the number is closer to 50,000 pounds, a large portion of which consists of Asian food wholesalers. "We literally got in on the ground floor," he remarks.

Doyle attributes the increasing consumption of specialty mushrooms to the globalization of food tastes, including a greater interest in Asian cuisine. Typically, upscale restaurants introduce diners to specialty ingredients, everything from balsamic vinegar to fresh herbs to mushrooms, which then start showing up on grocery store shelves. "The American palate has gotten a lot more sophisticated and interesting," Doyle says.

He also touts mushrooms' health benefits—they're a good source of nutrients and fiber, while also being low in carbohydrates and fat. Mushrooms provide more protein than most produce, and their hearty texture and savory, umami-rich flavor make them a popular meat substitute. Plus, the sheer variety of mushrooms makes them an attractive category to a certain zealous foodie personality. When Doyle used to sell mushrooms at the St. Joseph's farmers' market, fungi fanatics drove up from the Twin Cities to get their hands on obscure hedgehog or cauliflower mushrooms.

Inside Forest's oyster mushroom "fruiting" room, hundreds of compost-stuffed plastic bags hang on racks, looking rather like pint-size punching bags sprouting mushroom clusters. The room's few windows are covered with plastic to block direct sunlight (mushrooms don't photosynthesize), and the air feels like a foggy day in San Francisco: cool, damp, and clammy.

While wild mushrooms seem to crop up almost spontaneously, mushroom cultivation is a finicky business, as each variety grows optimally within a narrow climate range. For Forest's oyster mushrooms, Doyle keeps the long, narrow room at 63 degrees and 90 percent humidity.

Overhead, a constant rush of fresh air streams into the room. When mushrooms break down organic material, they give off CO2, which could build to crop-killing levels within a few hours if the fans were to malfunction. While the average home or office building completes one or two air exchanges a day, the fruiting room's ventilation system completes between six and ten in just one hour. (Don't feel guilty about your mushroom-consumption carbon footprint, as the C02 from natural decomposition of surface vegetation isn't nearly as big of a problem as burning fossil fuels.) Several sensors constantly monitor the climate conditions, and Doyle wears a pager to alert him in case of a system failure.

The adjacent shiitake fruiting room is darker and more cave-like, with mushrooms sprouting on what look like shelves upon shelves of burnt loaves of bread—they're actually substrate blocks made from oak sawdust and grain. As Doyle picks up one of the blocks to check the mushrooms' maturity, he jokes that the life of a mushroom grower is like that of a dairy farmer: Just as cows must be milked daily, the mushrooms must be picked daily. The shiitake blocks and oyster bags each produce three crops over a few weeks. For the oysters, each bag averages about five pounds of mushroom. When the cycle is complete, the contents of the leftover bags are sold to gardeners as mulch.

One of the biggest challenges with cultivating mushrooms is keeping harmful molds from destroying the crop. "You're creating a hospitable environment that's absolutely perfect for a lot of organisms," Doyle says. Concerned that molds were spreading from his compost-making to mushroom-growing buildings, Doyle gave up the straw-spinning portion of his Rumpelstiltskin role and now buys substrate from other companies.

While agri-hobbyists may tend their own chicken flocks and tap their own maple trees, it's unlikely that home mushroom cultivation will become the next hot foodie trend. While foraging for wild mushrooms is increasing in popularity, Doyle stresses the importance of education and experience. Foragers who sell wild mushrooms to restaurants or at farmers' markets are supposed to be state certified, as Doyle is, though regulation of most sellers has been somewhat lax. To avoid bug-infested mushrooms, or worse, poisonous ones, a thorough understanding of mycology is essential. For every edible mushroom variety that foragers seek, Doyle notes, "there are two to three that look similar that can be poisonous." 

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