Major Groups > Gilled Mushrooms > Pale-Spored > Floccularia


The Genus Floccularia  

[ Basidiomycetes > Agaricales > Tricholomataceae . . . ]

by Michael Kuo

Why are these six mushrooms not in the genus Tricholoma? Because they have amyloid spores. Never mind that other genera (Amanita, for example) manage to hold species with both amyloid and inamyloid spores. And never mind that the sole character separating the genus Floccularia thus involves the color reaction of its spores, as seen by the human eye through a microscope, to an obscure reagent that contains a date-rape drug, and that no one--no one, I tell you--has a theory about why such color reactions might accurately reflect the evolution of mushrooms.

No, my friends, Floccularia it is, defined by the following features:

  • Terrestrial habitat and mycorrhizal association with trees.
  • White spore print.
  • Stature not diminutive.
  • Gills attached to the stem or beginning to run down it.
  • Flesh continuous through cap and stem.
  • Partial veil present, creating a fairly persistent ring or sheath on the stem.
  • Pileipellis a cutis composed of filamentous hyphae (don't ask).

Floccularia straminea

Floccularia fusca

Floccularia albolanaripes

. . . and if you're wondering why Tricholoma caligatum is not, therefore, a Floccularia, we can add the following monumental feature:

  • Spores amyloid.

My little tirade aside, these are some pretty awesome mushrooms (especially Floccularia straminea), regardless of what genus they belong to. They are apparently limited to western North America, from the Rocky Mountains to the West Coast. Did I mention that they used to be species of Armillaria, and that the only way you'll find these mushrooms in field guides is to use this now-outdated genus name?

Key to 6 species, varieties, and forms of Floccularia in North America

1.Yellow shades present on the gills or cap, at least by maturity.

1.Yellow shades absent from gills and cap in all stages of development.

2.Young cap bright yellow and prominently scaly.

2.Young cap dull yellow or brownish, smooth or with appressed fibers but not prominently scaly.

3.Edge of the cap fairly bright yellow at maturity.

3.Edge of the cap not bright yellow at maturity.
Floccularia pitkinensis

4.Cap grayish to grayish brown.

4.Cap white.

5.Young cap prominently scaly.
Floccularia straminea var. americana f. alba

5.Young cap smooth or with appressed fibers.
Floccularia albolanaripes f. alba


Mitchel, D. H. & Smith, A. H. (1976). Notes on Colorado fungi II. Species of Armillaria (Fr.) Kummer. (Agaricales) Mycotaxon 4: 513-533.

Mitchel, D. H. & Smith, A. H. (1978). Notes on Colorado fungi III: New and interesting mushrooms from the aspen zone. Mycologia 70: 1040-1063.

Thiers, H. D. & Sundberg, W. J. (1976). Armillaria (Tricholomataceae, Agaricales) in the western United States including a new species from California. Madrono 23: 448-453.

Volk, T. J. & Burdsall, H. H. (1995). A nomenclatural study of Armillaria and Armillariella species (Basidiomycotina, Tricholomataceae). Synopsis Fungorum 8.

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

Cite this page as:

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

© MushroomExpert.Com