These things can get big—really big. Salvatore Terracina, a farmer, encountered a specimen nearly
8' (2.4 m) in circumference, 20" (50 cm) thick, and weighing 42 pounds, near the north coast of Sicily!
Typically these don’t exceed 8 inches in diameter.
Oyster mushrooms are natives of North America, as well as temperate or subtropical
forests throughout the world. They were first cultivated in Germany during World War I. The beautiful young
cultivated ones shown here are courtesy of the Fat Moon Farm in Westford, Massachusetts.
”Oyster mushroom” also applies
to several relatives, including but not limited to
yellow oysters and pink oysters.
Identification: Oyster mushrooms grow out of the sides of trees, bending
upwards so their caps are level, in thick clusters. The “stem” of each mushroom resembles the bell of a trumpet,
with white parallel gills running along the length. (The “stipe,” or true stem, is not always visible; if visible,
the base can be hairy.)
Caps are tan or gray when young, becoming paler as they
expand, and are typically 1½-6" (4-15 cm) in diameter. At first, they are more or less dome-shaped, but
the dome flattens with age, becoming indented on the top or fan-shaped and wavy. They are
quite variable in appearance.
They favor hardwoods, both living and dead, but rarely appear on conifers as well. They appear from early
Fall to mid-winter. Spore prints
are whitish, lilac, or grayish.
Oyster mushrooms have a slight, characteristic odor likened to that of anise or bitter almonds, and due to the presence of
a small amount of benzaldehyde.
Edibility: Oyster mushrooms don’t just look like their namesake, they taste
a little like osyters too. They are frequently used in Japanese, Korean, Indian, and
Chinese cuisine, and are rapidly growing in popularity in America as well. They are used in soups and
stir-fry recipes. Here are a few recipes.
They should be harvested young for eating.
Warning from Wikipedia: Omphalotus nidiformis is a toxic lookalike found in Australia and Japan. In North America, Omphalotus olivascens, the western jack-o’-lantern mushroom, and Clitocybe dealbata, the ivory funnel mushroom, both bear a resemblance to Pleurotus ostreatus. Both Omphalotus olivascens and Clitocybe dealbata contain muscarine and are toxic.
Online References:
Pleurotus ostreatus on Tom Volk's Fungi site, at the Department of Biology at the University of Wisconsin
Roughly 75 people in North America are poisoned each year by mushrooms, often from eating a poisonous species that resembles an edible species. Though deaths are rare, there is no cure short of a liver transplant for severe poisoning. Don’t eat any mushroom unless you are absolutely certain of its identity! Please don’t trust the identifications on this site. We aren’t mushroom experts and we haven’t focused on safely identifying edible species.
ID is uncertain 
