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Agaricus buckmacadooi

[ Basidiomycota > Agaricales > Agaricaceae > Agaricus . . . ]

by Michael Kuo

Agaricus buckmacadooi is a fairly large West-Coast species of Agaricus, found in hemlock and Douglas-fir forests in Washington, and in coast redwood forests in California. Its cap features small, dark brown scales at maturity, and it has a thick, rubbery ring on its stem.

A similar species, Agaricus deardorffensis, is also found on the West Coast; its cap is paler brown and less prominently scaly; it is also more prone to yellow staining on and inside the stem, and has slightly shorter spores. West Coast field guides and websites appear to combine Agaricus deardorffensis and Agaricus buckmacadooi in treatments of the former—and older West Coast guides often treated both species together as "Agaricus praeclaresquamosus."


Ecology: Saprobic; growing gregariously under coast redwood, Douglas-fir, or hemlock; fall and winter; Oregon and California. The illustrated and described collection is from California.

Cap: 8–20 cm; convex, becoming broadly convex or nearly flat; dry; scaly with dark brown scales over a pale, creamy brownish ground color; with a dark center at maturity; not bruising when rubbed.

Gills: Free from the stem; crowded; short-gills frequent; pinkish when young, becoming dark brown; when in the button stage covered with a whitish partial veil.

Stem: 8–14 cm long; 3–4 cm thick; club-shaped; more or less bald; with a whitish, skirtlike ring; whitish, discoloring brownish; basal mycelium white.

Flesh: White; unchanging when sliced.

Odor and Taste: Not distinctive.

Chemical Reactions: KOH yellow on cap surface.

Spore Print: Dark brown.

Microscopic Features: Spores: 5.5–7 x 4–4.5 µm; ellipsoid; smooth; thick-walled; brown in KOH; brown in Melzer's. Basidia 4-sterigmate. Cheilocystidia 20–35 x 4–12 µm; clavate, subclavate-cylindric, or nearly subcapitate; smooth; thin-walled; hyaline in KOH. Pleurocystidia not found. Pileipellis a cutis.

REFERENCES: R. Kerrigan, 2016. (Kerrigan, 2016.) Herb. Kuo 01151504.

This site contains no information about the edibility or toxicity of mushrooms.


Agaricus buckmacadooi

Agaricus buckmacadooi

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Kuo, M. (2018, April). Agaricus buckmacadooi. Retrieved from the MushroomExpert.Com Web site: