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Pleurotus pulmonarius: The Summer Oyster
by Michael Kuo
The separation of Pleurotus pulmonarius from the infamous "true" oyster mushroom, Pleurotus ostreatus, is based on very good evidence that covers the three "species concepts" most commonly applied to fungi. In the laboratory, Pleurotus pulmonarius cannot "mate" with the other species in the oyster complex, so it is a good biological species. It also represents a fairly distinct morphological species, since it is paler (and frequently smaller) than the brownish Pleurotus ostreatus and appears to develop more of a stem, more of the time. DNA evidence supports Pleurotus pulmonarius as a phylogenetic species and, to top it all off, there is an ecological difference: it appears in warmer weather than Pleurotus ostreatus, which favors cold-weather conditions.
Pleurotus populinus is also virtually identical, but it grows only on the wood of Populus species (aspens and cottonwoods). Pleurotus pulmonarius will grow on the wood of virtually any hardwood, including aspens and cottonwoods--in which case the larger spores of Pleurotus populinus will help separate the species.
Ecology: Saprobic; growing in shelf-like clusters on dead and living wood of hardwoods; causing a white rot; beginning in summer (unlike Pleurotus ostreatus) but continuing into fall and winter; widely distributed in North America.
Cap: 2-12 cm; convex, becoming flat or somewhat depressed; lung-shaped (hence its Latin name) to semicircular, or nearly circular if growing on the tops of logs; somewhat greasy when young and fresh; fairly smooth; whitish to beige or pale tan, usually without dark brown colorations; the margin inrolled when young, later wavy and, unlike Pleurotus ostreatus, very finely lined.
Gills: Running down the stem; close or nearly distant; whitish.
Stem: Sometimes absent or rudimentary, but often present; 1-7 cm long and up to 1.5 cm thick; eccentric or lateral--or central.
Flesh: Thick; white.
Odor and Taste: Odor distinctive but hard to describe ("like oyster mushrooms" works well, but makes for a circular description); taste mild.
Chemical Reactions: KOH on cap surface orangish.
Spore Print: Whitish, grayish or lilac.
Microscopic Features: Spores 7-10 x 2.5-5 µ; smooth; cylindric to long-elliptical.
Further Online Information:
Cite this page as:
Kuo, M. (2009, April). Pleurotus pulmonarius: The summer oyster. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/pleurotus_pulmonarius.html