Every year at this time, oyster mushrooms appear from the stumps and fallen logs of cottonwoods along the Bitterroot River. This particular species (Pleurotus populinus) had inoculated a downed cottonwood.
Ecology: Saprobic; growing in shelf-like clusters on dead and living wood of Populus species, primarily quaking aspen; causing a white rot; spring, summer, and fall; widely distributed in northern and montane North America, throughout the range of the host trees.
Cap: 2-15 cm; convex, becoming flat or somewhat depressed; kidney-shaped to fan-shaped, or nearly circular if growing on the tops of logs; somewhat greasy when young and fresh; smooth; whitish to pinkish gray or pale tan, without dark brown colorations; the margin inrolled when young, later wavy.
Gills: Running down the stem; close or nearly distant; whitish.
Stem: Usually absent or rudimentary, when the mushroom is growing from the side of a log or tree. When it grows on the tops of logs or branches, or at an angle, however, it may develop a substantial and thick stem that is dry and slightly hairy near the base.
Flesh: Thick; white.
Odor and Taste: Odor distinctive but hard to describe; taste mild.
Chemical Reactions: KOH on cap surface negative to yellowish.
Spore Print: Whitish (never lilac).
Microscopic Features: Spores 9-12 x 3-5 µ; smooth; cylindric to long-elliptical. Compare with measurements for the epitype collection of Pleurotus ostreatus, rather than measurements quoted in most field guides.
The delicious gems are a definite with their deep, earthy flavor that pairs perfectly with beef. I cooked the oyster mushrooms with slices of prime rib in a reduction of red wine with onions, garlic, and sage. Simple…delightfully.