Pleurotus ostreatus (Jacq.) P. Kumm. - Oyster Mushroom

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Agaricales - Family: Pleurotaceae

Pleurotus ostreatus - Oyster Mushroom

So variable in size, shape and colour are the many kinds of oyster mushroom that confident identification of some species is tricky without resorting to microscopic analysis. The process is not helped by the fruiting habit of many Pleurotus species that seem to delight in emerging beyond reach, sometimes high up in the crowns of trees.

For the most part the various oyster mushrooms are saprophytic on deciduous trees, and only very rarely are they found on conifers.

Oyster Mushrooms on a 'Cabage Tree', Isle of Bute

Distribution

Pleurotus ostreatus, the Oyster Mushroom, occurs throughout Britain and Ireland as well as in most parts of mainland Europe. It is also widely distributed throughout much of Asia, including Japan, and is present in parts of North America.

Several similar species within the Pleurotus genus are often confused, and so distribution data for individual species in this complex group are inevitably subject to some uncertainty.

Taxonomic history

The Oyster Mushroom was first described scientifically in 1775 by Dutch naturalist Nikolaus Joseph Freiherr von Jacquin (1727 - 1817) and named Agaricus ostreatus. (In the early days of fungus taxonomy most of the gilled mushrooms were included in the genus Agaricus.) In 1871 German mycologist Paul Kummer transferred the Oyster Mushroom to the genus Pleurotus (a new genus that Kummer himself had defined in 1971), giving it its currently accepted scientific name.

Pleurotus ostreatus, Oyster Mushroom, on a fallen branch

Synonyms of Pleurotus ostreatus include Agaricus ostreatus Jacq., Crepidopus ostreatus (Jacq.) Gray, and Pleurotus columbinus Quel. The blue-grey-capped form of this mushroom is referred to by some authorities as Pleurotus ostreatus var. columbinus (Quel) Quel.

Etymology

The generic name Pleurotus is Latin for ‘side ear’ and refers to the lateral attachment of the stem; ostreatus is a reference to oysters, and in shape the fruitbodies often do resemble oyster shells.

The specimens shown on this page demonstrate just how variable Oyster Mushrooms can be - not only in colour and form but also in their growing habitat. From the top: on a dead Beech trunk; next on a standing live (but surely dying) Cabbage Palm; and finally on a dead branch broken fallen from an old Ash tree.

Identification guide

Pleurotus ostreatus var columbinus

Cap

White, cream, brown, or blue-grey (var. columbinus - picture, left); usually bracket-like with either a radial stem or an eccentric stem; convex gradually becoming centrally depressed with a wavy margin; 5 to 18cm across; often in overlapping groups but with each stem separately attached to the substrate.

Gills of Pleurotus ostreatus, Oyster Mushroom

Gills

White, turning pale ochre with age; crowded; decurrent.

Stem

White or cream; woolly at base; sometimes stemless but usually with short stems 1 to 3cm long and 1 to 2cm diameter; tapering towards the base; no stem ring.

Spores of Pleurotus ostreatus, Oyster Mushroom

Spores

Subcylindrical to narrowly kidney-shaped, smooth, 8-12.5 x 3-4.5µm.

Show larger image

Spore print

White or more often pale lilac-grey.

Odour/taste

Smell and taste pleasant but not distinctive.

Habitat & Ecological role

Oyster Mushrooms are sometimes weakly parasitic but more often saprobic and found on dying or dead standing deciduous broadleaf trees, particularly Beech and oaks and sometimes on fallen trunks and large branches.

Season

Summer, autumn and early winter in Britain and Ireland; Oyster Mushrooms have a longer season in parts of southern Europe, where these edible fungi can sometimes be found through to January or February.

Similar species

Pleurotus dryinus has a frosted cap; its stem has a short-lived ring.

Pleurotus ostreatus, Oyster Mushroom, on a fallen beech trunk, Scotland

Culinary Notes

Pleurotus ostreatus, the Oyster Mushroom, is edible and is said to taste like its bivalve namesake as well as copying its shape; it is very similar in texture, too - rather flaccid compared with, say, familiar Agaricus species such as Field Mushrooms. These mushrooms are now produced in cultivation and readily available in supermarkets in Britain and Ireland, while in many European countries wild Oyster Mushrooms are much sought after in deciduous forests. We enjoy them in mixed mushroom meals, but on their own the texture of Oyster Mushrooms is rather limp and not our favourite.

Reference Sources

Pat O'Reilly (2016) Fascinated by Fungi; First Nature

British Mycological Society, English Names for Fungi

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi and (for basidiomycetes) on Kew's Checklist of the British & Irish Basidiomycota.

Acknowledgements

This page includes a picture kindly contributed by Richard Haynes.

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