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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.


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 µ; 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 µ; capitate to subcapitate; hyaline in KOH; thin-walled. Pleuro-chrysocystidia scattered; often scarcely projecting; 30-50 x 10-15 µ; 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 µ 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.

Psilocybe aeruginosa is a synonym.

Further Online Information:

Stropharia aeruginosa at Roger's Mushrooms


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: