Oyster mushrooms are common fungus on deciduous trees

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By Ted Manzer

Friday, January 18, 2019

A friend of mine brought in a mushroom sample recently for me to identify. I smiled when I saw it. When I was a teenager, it was one of my favorites to collect. I usually found it on dead or dying elm trees.

It’s called oyster mushroom and it’s one of the most abundant in North America. These mushrooms are tree-rotting fungi, but they don’t kill healthy trees. Usually trees are already stressed and dying before oyster mushroom spores invade them.

These fungi are saprophytic. That means they break down tissue that is already dead. Parasitic species attack living tissue.

I have been hesitant to write about collecting wild mushrooms for fear I might encourage someone to partake some without proper training. Many edible species are abundant, but so are many questionable ones. One mistake is all it takes to stumble into a disaster.

Even this oyster mushroom has one lookalike that could pose a problem for mycological newbies. It’s called the angel wing mushroom and it grows strictly on pines and related conifers. Both these mushrooms have a clamshell appearance. Angel wing fruiting bodies are white with a white spore print. Oyster mushrooms are cream colored to tan, also with a white spore print.

Angel wing fungi have much thinner flesh than oyster mushrooms do. They also have very little odor. Some mycologists describe oyster mushroom scent as anise-like. I think they have a seafood smell when raw. That’s why I always thought they were called oyster mushrooms. Most literature reports their overall physical appearance to be oyster-like.

Oyster mushrooms and angel wing mushrooms both have what we call gills on their lower sides. Gills are parallel slits on the undersides of the fleshy caps. Both also don’t have a true stem-like structure called a stipe. Parallel gills run the entire length of the cap on both.

I like to collect oyster mushrooms for several reasons. Usually they can be found in great abundance. A bushel or more on a single tree is not uncommon. They have nice flavor and freeze and can well. I think they are too thick fleshed to make good drying mushrooms.

They are best if cooked. Raw ones are too chewy. I sauté them in butter or olive oil and season them with a little salt and garlic. According to many sources they are a rich source of antioxidants and even contain chemicals that reduce bad blood cholesterol. Research also indicates blood glucose levels can be reduced by this fungus.

Except for the angel wing mushroom, I can’t think of anything else that strongly resembles oyster mushrooms. Oysters only grow on deciduous trees. Around here we find them mostly on beech, cottonwood and sweetgum. They are sometimes spotted on oak, hickory and other hardwoods.

As with any type of food, even if you trust the source don’t ever eat much the first time. Some people have no reaction while others could get quite sick. Mushrooms especially are nothing to play with. Always confirm the identification with an expert or maybe two.

Ted Manzer teaches agriculture at Northeastern High School.