What You Should Know
Pholiota squarrosa has a hat that is yellow-white and covered with brown scales. The gills are light yellow to brown. The foot is the same color as the hat and protruding scales.
This poisonous mushroom appears at the bases of old trees and sometimes on the stumps of felled trees - mainly broadleaf species but also occasionally conifers, notably spruces.
The Shaggy Scalycap is often confused with Honey Fungus (Armillaria mellea and similar species). The two groups can be distinguished easily by taking a spore print: Armillaria species produce white spore prints while all Pholiota fungi have brown spores.
Other names: Dry Scaly Pholiota, Shaggy Scalycap, Shaggy Pholiota, The Scaly Pholiota.
Pholiota squarrosa Mushroom Identification
Saprobic and possibly parasitic; growing in clusters on the wood of hardwoods or conifers; often found at the bases of living or dead trees; especially common on aspens and spruces in the Rocky Mountains; summer and fall; fairly widely distributed in North America.
3-12 cm; convex, becoming broadly convex or broadly bell-shaped; dry; yellowish underneath conspicuous buff to tawny scales.
Attached to the stem or beginning to run down it; close or crowded; whitish to yellowish when young, becoming greenish-yellow and eventually rusty brown; at first, covered by a partial veil.
4-12 cm long; up to 1.5 cm thick; dry; with an ephemeral ring or ring zone; yellowish, sometimes becoming brown to reddish-brown from the base up; covered with a conspicuous buff to tawny scales.
Whitish to yellowish.
Odor and Taste
Odor not distinctive or strongly of garlic; taste mild or somewhat unpleasant. The odor of my collections in Colorado is quite strong and quite distinctive--like a cross between garlic and lemon.
KOH negative on cap surface.
Spores 6-8 x 4-5 µ; smooth; more or less elliptical; with an apical pore; reddish-brown in KOH. Pleurocystidia clavate to clavate-mucronate or subfusiform; some with refractive contents in KOH; to 45 x 14 µ. Cheilocystidia subfusiform to fusoid-ventricose or clavate; to 43 x 15 µ. Pileipellis an interwoven layer of cylindric hyphae with clavate to fusoid-ventricose terminal elements. Clamp connections present.
Pholiota squarrosa Similar Species
Pholiota squarrosa is similar in appearance to species in the genus Armillaria, but the latter produces white spore prints.
Another similar mushroom is Pholiota squarrosoides, which can be distinguished microscopically by its smaller spores, and macroscopically by the stickiness of the cap between the scales.
P. squarrosoides also lacks the odor of P. squarrosa, and has flesh that is white, not yellow. Leucopholiota decorosa can also be misidentified with P. squarrosa; it has white, adnexed gills with finely scalloped edges, but it can be distinguished most reliably by its white, nonamyloid spores.
Pholiota squarrosa Taxonomy and Etymology
This species was described in 1771 by the German scientist Christian Ehrenfried Weigel (1748 - 1831) who named it Agaricus squarrosus - in the early days of fungal taxonomy most gilled mushrooms were placed in the genus Agaricus, which was later broken up into many other genera that we use today. The Shaggy Scalycap was transferred to its present genus by German mycologist Paul Kummer in 1871, at which time its scientific name became Pholiota squarrosa.
Pholiota squarrosa is the type species of the genus Pholiota, which contains some 150 known species worldwide. Fungi in this group generally have glutinous cap surfaces, especially in wet weather, and usually, scales cover part or all of the cap surface and often also the stem. Their brown (in mass) spores are smooth-surfaced ellipsoids each with a germ pore.
Synonyms of Pholiota squarrosa include Agaricus floccosus Schaeff., Agaricus squarrosus Weigel, Lepiota squarrosa (Weigel) Gray, Agaricus verruculosus Lasch, and Dryophila squarrosa (Weigel) Quél.
Derived from the Greek word Pholis, meaning a scale, the generic name Pholiota means scaly.
The specific epithet squarrosa adds just a little more detail because it translates to 'with upright scales'.
Pholiota squarrosa Chemistry
The fruit bodies contain unique chemical compounds that are derived from phenylpropanoids. The compounds, named squarrosidine and pinillidine, inhibit the enzyme xanthine oxidase.
Xanthine oxidase catalyzes the crystallization of uric acid in the joints, the main cause of gouty arthritis, and inhibitors of this enzyme are being used clinically to reduce this side effect. The natural function of these compounds may be to quench reactive oxygen species produced by plants as a defensive response to fungal infection.
Photo 1 - Author: Villy Fink Isaksen (Creative Commons Attribution-Share Alike 3.0 Unported)
Photo 2 - Author: Holger Krisp (Creative Commons Attribution 3.0 Unported)
Photo 3 - Author: Holger Krisp (Creative Commons Attribution 3.0 Unported)
Photo 4 - Author: Lukas from London, England (Creative Commons Attribution-Share Alike 2.0 Generic)