Oyster Mushroom

Photo of oyster mushrooms growing on a tree trunk
Safety Concerns
Scientific Name
Pleurotus ostreatus and P. pulmonarius

Gilled, in shelflike clusters; broad, fleshy, whitish, grayish, or tan cap; stubby, off-center stalk. Grows on stumps, logs, and trunks of deciduous trees. Year-round. Cap shell-shaped, semicircular to elongated; margin is smooth, sometimes wavy; whitish to grayish to tan; texture velvety; flesh is thick, white. Gills narrow; spacing nearly distant; white, becoming yellowish; attachment descending the stalk. Stalk (if present) short, thick; white; base is hairy; off-center, solid. Spore print white to grayish-lilac. Spores magnified are narrowly elliptical, smooth, colorless.

There are no lookalikes in Missouri that are poisonous.

Cap width: 1–6 inches; stalk length: to 1¼ inches; stalk width: to ¾ inch.
Where To Find
image of Oyster Mushroom distribution map
Grows in clusters on stumps, logs, and trunks of deciduous trees. P. ostreatus fruits year-round, especially after a good rain, if the weather is mild. P. pulmonarius fruits only during warm months. It is occasionally covered with a bright yellow slime mold. Oyster mushrooms sometimes appear to "smoke" from the mass release of spores. A single "oyster log" can refruit several times a season.
Considered a choice edible, wild oyster mushrooms have a much better flavor than the cultivated oyster mushrooms found at most grocery stores. That said, easy-to-use kits for growing oyster mushrooms at home are available, and these are educational, fun, and provide healthful food for the table.
Life Cycle
The mycelium (network of fungal cells) of oyster mushrooms actually kills and eats some kinds of nematodes, plant parasites that damage plant roots. The nematodes provide the fungus with nitrogen, a nutrient that is otherwise difficult to break down in wood. The nematode-trapping ability is being studied as a possible biocontrol to prevent plant diseases caused by certain nematodes.

This prized culinary mushroom has many proven health benefits.

It is also being explored as a "digester" of inorganic waste and as an environmentally responsible substitute for Styrofoam. The mycelium is grown in molds filled with waste grain, then heat-treated to stop growth when the mold is full.

People have found they can grow these choice edible mushrooms on coffee grounds and spent grain from beermaking.

This is one of the many fungus species that live on decaying wood. It and other such saprobic fungi play an incredibly important role in breaking down the tough materials wood is made of and returning those nutrients to the soil.

An orange-and-black pleasing fungus beetle, Triplax thoracica, is often found on oyster mushrooms.

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Similar Species
About Mushrooms in Missouri

Mushrooms are a lot like plants, but they lack chlorophyll and have to take nutrients from other materials. Mushrooms are neither plants nor animals. They are in a different kingdom — the fungi. Fungi include the familiar mushroom-forming species, plus the yeasts, molds, smuts, and rusts.

Always be cautious when eating edible mushrooms. Be absolutely sure of the ID, and only eat a small amount the first time you try it to avoid a reaction..