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Floccularia straminea

[ Basidiomycetes > Agaricales > Tricholomataceae > Floccularia . . . ]

by Michael Kuo

You know you are married to the most wonderful woman on earth when you are cruising along a high mountain pass and she screams Stop! Mushroom! after spotting Floccularia straminea from 30 feet away at 40 miles per hour. She always finds the cool ones, while I can walk around for hours and find only a Marasmius.

Floccularia straminea is a western species, fairly commonly encountered in Quaking Aspen stands, but also making frequent appearances in spruce-fir forests. When young and fresh it is a gorgeous bright yellow, and its cap and stem are adorned with large, soft scales. Other defining features include its terrestrial habitat, its attached gills, and its amyloid spores.

The official name for our North American species is Floccularia straminea var. americana f. americana--or simply Floccularia luteovirens. You are welcome to use either of these names if you prefer (but be sure to read the comments below first).


Ecology: Probably mycorrhizal; growing alone, scattered, or gregariously in stands of Quaking Aspen or in spruce-fir forests; summer and fall in the Rocky Mountains; fall and winter on the West Coast.

Cap: 4-18 cm; convex or nearly round when young, becoming planoconvex, flat, or broadly bell-shaped; dry; conspicuously scaly with soft, vaguely concentrically arranged scales, especially in the outer half; bright yellow when young, but often fading to straw yellow or pale yellow; the edge adorned with partial veil remnants.

Gills: Attached to the stem; close; yellow to pale yellow.

Stem: 4-12 cm long; up to 2.5 cm thick; more or less equal; white and smooth near the apex; sheathed below with shaggy zones of soft yellow scales in roughly concentric zones; sometimes with a flimsy ring.

Flesh: White; not changing on exposure.

Taste: Not distinctive; odor not distinctive.

Spore Print: White.

Chemical Reactions: KOH on cap surface negative; KOH and iron salts on flesh both negative.

Microscopic Features: Spores 6-8 x 4-5 µ; smooth; elliptical; amyloid.

REFERENCES: (Mitchel & Smith, 1976) Bon, 1990. (Mitchel & Smith, 1976; Smith, Smith & Weber, 1979; States, 1990; Phillips, 1991/2005; Lincoff, 1992; Evenson, 1997.) Herb. Kuo 08060509, 08150701.

An "albino," white form is given the name Floccularia straminea var. alba. See the comments on Floccularia albolanaripes for help separating it from that species' albino form.

An enormous taxonomic mess surrounds the naming of this mushroom. Our western species was originally labeled Armillaria luteovirens, but Mitchel & Smith (1976), after studying the insufficient and vague original descriptions of Armillaria luteovirens in Europe, were "forced to conclude that the original description of A. luteo-virens cannot, within reason, apply to our Colorado mushroom." The authors wound up applying the name Armillaria straminea var. americana. Then Armillaria collapsed, and hundreds of its species were transferred to other genera; Armillaria straminea wound up in Floccularia on the basis of its amyloid spores and mycorrhizal role. Now, according to the Index Fungorum, all the straminea names have been synonymized with Floccularia luteovirens--but the citation for the transfer of Mitchel & Smith's taxon is from 1957, 20 years before they published Armillaria straminea var. americana, in a European publication in which the European species Armillaria straminea was deemed synonymous with Armillaria luteovirens. Mitchel and Smith (p. 516), however, took pains to point out substantial morphological differences from Armillaria luteovirens:

    [T]he pileus was in no way pulverulent . . . the consistency was not hard . . . in no way can 'sordide lutescente-viridi' be considered the equivalent of lemon to chrome yellow, and lamellae up to 12 mm broad cannot be interpreted as narrow.

If you're gripping the edge of your seat and want more on the "proper" name for this mushroom, check out the entries for "straminea," "americana," and "luteovirens" in Volk & Burdsall's 1995 paper, "A nomenclatural study of Armillaria and Armillariella species," which is online here. Meanwhile, I will wait for a molecular comparison between European and North American taxa, and find something better to do with my time.

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


Floccularia straminea

Floccularia straminea

Floccularia straminea

Floccularia straminea

Floccularia straminea

Floccularia straminea

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Kuo, M. (2006, October). Floccularia straminea. Retrieved from the MushroomExpert.Com Web site: