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Stropharia caerulea

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

by Michael Kuo

This species is so blue, and so gorgeous, that you'd think it would be unmistakable. But a microscope is probably needed to separate it confidently from the very similar Stropharia aeruginosa. The principle feature separating these two species is the sterile cells on the edges of the gills: in Stropharia aeruginosa they are capitate and lack refractive contents, while in Stropharia caerulea they are widely fusiform and contain yellowish, refractive inclusions (which makes them "chrysocystidia"). This difference can sometimes be assessed with the naked eye, since the capitate, non-refracticve cheilocystidia of Stropharia aeruginosa tend to make the edges of the gills whitish, contrasting with the faces of the gills. But when the gills of both species are young they are whitish all over—and when they're very mature the purplish brown spores usually manage to cover the gill edges, too, so there is only a small window of opportunity to catch Stropharia aeruginosa in its identifiable-by-naked-eye stage.

Stropharia cyanea, in the sense of some authors, is a synonym. Psilocybe caerulea is a synonym. Agaricus impolitus is a former name.

Thanks to Alison Sampson for collecting, documenting, and preserving Stropharia caerulea for study; her collection is deposited in The Herbarium of Michael Kuo.


Ecology: Saprobic, growing alone or gregariously; usually found in gardens, landscaping areas, and waste places; North American distribution uncertain. The illustrated and described collection is from Ontario.

Cap: 2–4 cm; bell-shaped at first, becoming broadly bell-shaped or nearly convex; very slimy when fresh; bald; when young and fresh, dark greenish blue; sometimes fading to yellowish green or developing yellowish areas and spots; the margin hung with whitish partial veil remnants, especially when young.

Gills: Broadly attached to the stem; close; short-gills frequent; whitish at first, becoming purplish gray to purple-brown; edges colored like the faces.

Stem: 3–5 cm long; 5–10 mm thick; equal above a slightly swollen base; sticky when fresh; with a faint ring zone (usually lacking a well-developed ring); pale above, colored like the cap below; basal mycelium white.

Flesh: White, or in the lower stem colored like the cap; unchanging when sliced.

Odor and Taste: Not distinctive.

Spore Print: Purplish brown.

Microscopic Features: Spores 7–9 x 4.5–5.5 µm; ellipsoid; smooth; pale brown in KOH; yellowish brown in Melzer's; with a very tiny pore. Chryso-cheilocystidia abundant; 30–40 x 10–12.5 µm; widely fusoid; hyaline in KOH; thin-walled; with yellowish-refractive inclusions. Chryso-pleurocystidia scattered; often scarcely projecting; 20–30 x 7.5–10 µm; subclavate to widely fusoid; hyaline and thin-walled; with yellowish-refractive inclusions. Pileipellis a thick ixocutis of hyaline to golden, poorly defined elements.

REFERENCES: Kreisel, 1979. (Bolton, 1788; Persoon, 1801; Breitenbach & Kränzlin, 1995; Noordeloos, 1995; Noordeloos, 1999.) Herb. Kuo 10171501.

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Stropharia caerulea

Stropharia caerulea

Stropharia caerulea

Stropharia caerulea

Stropharia caerulea

Stropharia caerulea

Stropharia caerulea

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