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Stropharia aeruginosa

[ Basidiomycota > Agaricales > Strophariaceae > Stropharia. . . ]

by Michael Kuo

The original author of this gorgeous species (Curtis, 1782) wrote that the mushrooms are the color of verdigris when young and fresh, but that, "alas! . . . it loses that verdigris green, which on its first appearance renders it so conspicuous, the cap being often found of a pale yellowish brown color." I have seen Stropharia aeruginosa only twice, and both times I arrived too late to see it in its vertigris prime. For illustrations of young, deeply blue-green specimens, a quick Internet image search will probably help—but I recommend Curtis's 1782 painting of the species.

The dramatic color change in Stropharia aeruginosa is reminiscent of the green-to-yellowish metamorphosis undergone by Gliophorus psittacinus, the "parrot mushroom." Unlike the parrot mushroom, however, Stropharia aeruginosa has purple-gray to purple-black gills, a purple-black spore print, and a sheathing ring on the stem (which often disappears with age). Microscopic features help to separate Stropharia aeruginosa from several similar species: it lacks chrysocystidia on its gill edges. (At least, that's the reigning theory; contemporary, DNA-based study of Stropharia aeruginosa and its close look-alikes has not yet happened.)

Stropharia caerulea is nearly identical to the naked eye—although, in theory, its gill edges are not whitish and contrasting, like those of Stropharia aeruginosa. Under the microscope, however, Stropharia caerulea has very different gill edges; they are lined with fusiform chrysocystidia, whereas the gill edges of Stropharia aeruginosa are lined with capitate, non-refractive cheilocystidia.

Stropharia pseudocyanea (also known as "Stropharia albocyanea") is very similar but features a poorly developed ring; its cap is usually much paler, when young, than the cap of Stropharia aeruginosa. Microscopically the two species are inseparable.

Psilocybe aeruginosa is a synonym.


Ecology: Saprobic, growing alone or gregariously under hardwoods or conifers, and sometimes in grass; also found on woody debris; summer and fall; not common; probably widely distributed in North America, at least as a species group. The illustrated and described collections are from Colorado and Illinois.

Cap: 3–5 cm; convex or broadly bell-shaped at first, becoming broadly convex, with or without a central bump—or nearly flat; very slimy when fresh; bald; when young deep blue-green, but soon fading to yellowish green and developing yellowish areas and spots; finally becoming brownish yellow overall; the marginal area often decorated with whitish partial veil remnants, especially when young.

Gills: Broadly attached to the stem but receding with maturity; close or, at maturity, nearly distant; short-gills frequent; whitish to pale gray at first, becoming purplish gray to purple-black; edges pale and contrasting.

Stem: 3–7 cm long; 5–10 mm thick; equal; dry; with a fragile, soon-disappearing, sheathing ring with a flared and ragged upper edge; often with white scales when young; pale above, colored like the cap below; basal mycelium white; attached to white rhizomorphs.

Flesh: Soft; white or colored like the cap; unchanging when sliced.

Odor and Taste: Odor fragrant and a bit foul (almost reminiscent of the "green corn" odor found in some species of Inocybe); taste not distinctive, or somewhat radishlike.

Chemical Reactions: KOH on cap surface dull yellow.

Spore Print: Purplish brown to purplish black.

Microscopic Features: Spores 6–10 x 3.5–5 µm; ellipsoid to slightly amygdaliform; smooth; pale, dull brown in KOH; yellowish brown in Melzer's; with a very tiny pore. Cheilocystidia abundant; 25–37.5 x 5–10 µm; capitate to subcapitate; hyaline in KOH; thin-walled. Pleuro-chrysocystidia scattered; often scarcely projecting; 30–50 x 10–15 µm; clavate to fusoid-ventricose or mucronate; hyaline and thin-walled; with yellowish-refractive inclusions. Pileipellis a thick ixocutis of hyaline to golden, smooth, cylindric elements 5–10 µm wide.

REFERENCES: (Curtis, 1782) Quélet, 1872. (Fries, 1821; Saccardo, 1887; Kauffman, 1918; Stamets, 1978; Smith, Smith & Weber, 1979; Arora, 1986; Phillips, 1991/2005; Lincoff, 1992; Barron, 1999; Noordeloos, 1999; McNeil, 2006; Miller & Miller, 2006; Knudsen & Vesterholt, 2008; Trudell & Ammirati, 2009.) Herb. Kuo 08150301, 09210602.

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Stropharia aeruginosa

Stropharia aeruginosa

Stropharia aeruginosa

Stropharia aeruginosa
Spore print

Stropharia aeruginosa

Stropharia aeruginosa

Stropharia aeruginosa
Basidia and pleuro-chrysocystidium

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Kuo, M. (2015, November). Stropharia aeruginosa. Retrieved from the MushroomExpert.Com Web site: