The Carlisle Mosquito Online

Friday, November 29, 2002


Photo by Kay Fairweather

Oyster mushroom

Name: Pleurotus ostreatus or oyster mushroom. The suffix —otus and —atus on a scientific name means resembling, similar to, or furnished with. In addition 'pleur' is beside or on the side and 'ostre' is oyster.

When and where found: November 23, in the Towle land on the side of a dead standing tree and also on a fallen log. On the standing tree, most were at the base and a small clump was growing about 8 feet up. I found oyster mushrooms on the same tree in October 2000 and again in October 2001. They are later this year perhaps because of the dry summer.

Distinguishing characteristics: Oyster mushroom caps are broad, fan-shaped, convex when young, flat or even funnel-shaped when older, and can reach a size of up to 7 inches across. The species name ostreatus refers to the look rather than the taste and indicates that they resemble oyster shells. The caps are smooth, cool and damp, and the color varies from near white to gray to brown. The gills are white and close together. If there is a stalk, it is short, firm, whitish, usually off-center, usually fuzzy at the base, and the gills descend the stalk. The spores are white or tinged with lilac.

Habitat: Oyster mushrooms generally grow in shelf-like clusters on the side of hardwoods. It is possible to find 10 or 20 pounds or more on the same tree. Pleurotus species are relatively easy to cultivate, partly because they are tolerant of sunlight and can grow on a variety of substrates, basically anything with cellulose — including crushed coffee beans, compressed sawdust, and shredded Time magazines. It could be worthwhile investigating an oyster mushroom corner at the Transfer Station. I feel an application for a research grant coming on.

Look-alikes: Another gilled, shelf-like mushroom with white spores is the Lentinellus ursinus which can be distinguished by the ragged, serrated edges of its gills. It is not tasty — it has the reputation of being the only mushroom that raccoons spit out. Pleurotus porrigens (Angel Wings) is a white, shelf mushroom with a white spore print, but is smaller and thinner than the oyster mushroom and it grows on conifers. Some Crepidotus species could be mistaken at first for small oyster mushrooms, but they have a brown spore print.

Edibility: Oyster mushrooms are quite delicious. If you don't want the extra protein, and you're not preparing for the next Survivor series, you might want to check between the gills for beetles, or buy the cultivated ones. In the stores, they are often called 'tree oysters.' Discard the stalks which can be tough.

References: Tom Volk's Fungi at, and Mushrooms Demystified by David Arora. For recipes, you'll get many hits from a web search engine, or you can check Steve Brill's Wild Vegetarian Cookbook at the Gleason Library.

Send Biodiversity Corner submissions to to Kay Fairweather at 392 School St., Carlisle MA 01741 or to

2002 The Carlisle Mosquito