• Imported to the US for culinary use, golden oyster mushrooms have since escaped into the wild and are rapidly spreading in Michigan
• The bad news is they’re displacing native fungi, with untold consequences for Michigan forests
• On the bright side, they’re delicious and easy to spot, making them a prime target for foragers

Let’s start with the bad news: A new invasive mushroom is on the loose in Michigan’s woods, rapidly displacing native fungi that play vital roles in the forest food web.

The good news? It’s edible, delicious and prolific. 

Golden oyster mushrooms, a yellow-hued delicacy native to Asia and Russia that escaped captivity in the early 2010s after being imported for culinary use, have since spread throughout the southern Lower Peninsula, 24 other states and parts of Canada.

“When it’s warm, they’ll just keep reflushing on the same tree over and over and over,” said Jennifer Rier, who prefers to pan-fry or dehydrate the mushrooms she forages near her home in Livingston County. 

While state officials urge residents to report sightings and avoid buying the at-home grow kits that may be a source of the invasion, scientists are scrambling to study the consequences.

What’s known so far isn’t encouraging: According to a recent study led by a University of Wisconsin-Madison fungal ecologist, the mushrooms appear to be outcompeting native fungi.

“A lot of people tell me that they no longer see their native oyster mushrooms around,” said Aishwarya Veerabahu, the study’s lead author. 

In forests near Madison, Veerabahu’s team found that logs colonized by oyster mushrooms contained about half as many native fungal species as oyster-free logs.

“The traits of those individual fungi determine how that wood gets broken down, whether it happens fast or slow, what residues or chemicals end up being created, all kinds of things,” Veerabahu said. 

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Those outcomes likely influence the broader forest ecosystem in important ways, she said. What’s more, many mushrooms contain unique traits or compounds that can be used to develop medicines or other useful products. 

“What kind of loss of undiscovered therapeutic chemicals are we losing by losing biodiversity to an invasive species?” Veerabahu said. 

While invasive plants and animals have long been a well-known problem, the University of Wisconsin-Madison study may be the world’s first to document environmental harm caused by a cultivated mushroom.

Nutty and nutritious, golden oysters — or Pleurotus citrinopileatus — have been cultivated commercially in the US for years, while their spores are packed into grow kits marketed to at-home chefs. They escaped captivity around the early 2010s and began spreading rapidly through North America’s woods, becoming a popular target for foragers.

“I just pop the caps off, briefly wash them down, get the bugs out, and put them in a pan of butter like I would with morels,” said Jessica Foust, who began noticing the invasive mushrooms on dead elms near her home in Hillsdale County two years ago.

But the delight in stumbling across a motherlode is mixed with concern about how golden oysters may impact the environment. 

“I hope it doesn’t get rid of my chicken of the woods and I hope it doesn’t get rid of the morels,” Foust said. “If it does, then it’s gotta go.”

Because golden oysters are not a restricted species in Michigan, it’s still legal to buy and sell the grow kits that may be contributing to the invasion. 

But just because you can doesn’t mean you should, said Joanne Foreman, a spokesperson for the Michigan Department of Natural Resources invasive species program.

“If you’re currently growing golden oyster mushrooms, I would say, stop,” Foreman said. “Once you harvest the last bit, bag them up and dispose of them very carefully. And whether it’s oyster mushrooms or another mushroom, if it’s not native to Michigan, don’t be growing them outside.”

But with oysters now releasing their spores throughout North America’s woods, humans may be powerless to stop the invasion. That’s because mushrooms can spread through airborne spores and root-like mycelium that weave deep into soil and decaying wood.

“It’s hard enough to try and get invasive plants like kudzu or an invasive animal like carp out of the environment,” Veerabahu said. “And at least their bodies start and end in a place that you can see.”

The mushrooms are just the latest in a long list of invasive species brought to Michigan with good intentions but devastating consequences. 

The state’s wetlands are being overrun with lesser celandine, a yellow-flowered European plant that was imported for use in gardens. Autumn olive, a shrub that soil conservation districts once promoted for erosion control and deer feed, is now choking out prairies. The emerald ash borer beetle is devastating forests. Invasive mussels are transforming the Great Lakes after arriving as stowaways on shipping freighters.

Foreman’s advice to Michiganders who want to avoid unwittingly causing the next invasion: “Stay native.”

Whether you’re buying garden plants, aquarium fish or mushrooms for your dinnerplate, she said, “you owe it to the environment to take a little time and learn what you can about the species.”

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