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Amanita pachycolea

[ Basidiomycetes > Agaricales > Amanitaceae > Amanita . . . ]

by Michael Kuo

This West-coast species is King among the North American members of the Amanita vaginata species group. Like the others it lacks a ring, and features a sacklike volva and a strongly lined cap--but it stands up to 25 cm high and sports a cap that can get as wide as 15 cm or more. Take a look at the "buttons" in the photos to the right, which seem boring enough--until you get your mind around the comparative size of the pennies!

Other distinctive features of Amanita pachycolea include its dark brown cap, which usually fades at the margin and often appears to have gradually darkening zones of color towards the center; the brownish stem; the gill edges, which have brownish edges at maturity; and microscopic features. It is found primarily in northern California, but is also documented from the Pacific coasts of Oregon, Washington, and British Columbia.


Ecology: Mycorrhizal with conifers; growing alone, scattered, or gregariously; fall and winter; coastal Northern California and northward along the Pacific Coast.

Cap: 7-18 cm, convex, becoming broadly convex or flat; sometimes with a central bump; sticky when fresh; dark brown overall when young, becoming paler toward the margin and often featuring concentric zones of color; usually naked but occasionally featuring a whitish patch; the margin prominently lined with striations that extend about a third of the way inward.

Gills: Free from the stem by maturity; whitish to grayish but sometimes darkening with age to pale brownish or orangish; close; at maturity usually featuring brownish edges; short-gills frequent.

Stem: 10-25 cm long; up to 3 cm thick; equal or tapering to apex; without a basal bulb; finely hairy or fairly smooth; whitish but discoloring grayish or brownish with age; without a ring; with a prominent, white, sack-like volva that may discolor rusty or brownish with age.

Flesh: White; not discoloring on exposure.

Odor: Not distinctive.

Spore Print: White.

Microscopic Features: Spores 9-14 x 9-12 µ; smooth; globose or subglobose; inamyloid. Basidia 4-spored; occasionally clamped. Pileipellis an ixocutis of hyphae 2-9 µ wide. Lamellar trama bilateral; subhymenium ramose.

REFERENCES: Stuntz in Thiers & Ammirati, 1982. (Smith, Smith & Weber, 1979; Thiers & Ammirati, 1982; Thiers, 1982; Arora, 1986; Jenkins, 1986; Trudell & Ammirati, 2009; Tulloss, 2013.) Herb. Kuo 01120612.

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


Amanita pachycolea

Amanita pachycolea

Amanita pachycolea

Amanita pachycolea

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Kuo, M. (2013, April). Amanita pachycolea. Retrieved from the MushroomExpert.Com Web site: