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Leucocoprinus birnbaumii

[ Basidiomycota > Agaricales > Agaricaceae > Leucocoprinus . . . ]

by Michael Kuo

I receive many frantic e-mails about this little yellow mushroom, since it has a tendency to pop up unexpectedly in people's flower pots--even indoors! I have only seen it once, many years ago, before I began studying mushrooms in earnest. So I have no photos of my own, nor have I studied preserved specimens. Ordinarily this would mean I would not make a page for the species at this website, but since the thing is so distinct, and since so many people want to know about it, I have done so anyway, using readers' photos and combining data on its physical features from sources in my library. Would you like to help me study this beautiful little thing? Let me know if you'd be interested in preserving some of your flower pot's little yellow jewels and sending them to me so that this page could be more scientific and better documented.

Leucocoprinus birnbaumii won't hurt you, unless you eat it. It won't hurt your plant. It won't hurt your pets or your children, unless they eat it. There is no getting rid of it, short of replacing all the soil in your planter (and even then it might reappear). Since it makes such a beautiful addition to your household flora, I recommend learning to love it--and teaching your children to love it, too.

You might also impart the idea that mushrooms are very, very cool--but shouldn't be eaten. Perhaps your child would like to become an awesome and famous mycologist some day. I would love to encourage your child's interest in mushrooms by putting his or her drawing of Leucocoprinus birnbaumii on this Web page (at least temporarily). Here's a drawing from 8-year-old Daniel in Queensland:

Leucocoprinus birnbaumii

Lepiota lutea is a previous name. There are several closely related species, including Leucocoprinus tricolor (with a brown cap center, pale yellow colors, and a chrome yellow stem base), Leucocoprinus flavescens (with a brownish cap center and smaller spores) and Lepiota fragilissimus, with an extremely thin cap and pale gills.


Ecology: Saprobic; growing alone, gregariously, or clustered in flower pots, greenhouses, and so on--or, in warm conditions, outside in gardens and other cultivated areas (often around stumps); also growing in hardwood and conifer forests, especially in disturbed ground areas (pathsides, etc.); outdoors in summer, indoors year-round; widely distributed in North America.

Cap: 2.5-6 cm across; oval when young, becoming broadly conical, broadly convex, or bell-shaped; dry; powdery to scaly; the margin lined or grooved nearly to the center; bright to pale yellow, often with a darker (but not brown) center.

Gills: Free from the stem; crowded; yellow to pale yellow.

Stem: 3-10 cm long; 2-5 mm thick; more or less equal above a slightly swollen base; dry; bald or powdery; with a fragile, bracelet-like, yellow ring that sometimes disappears.

Flesh: Whitish to yellowish; very thin.

Odor and Taste: Not distinctive.

Spore Print: White.

Microscopic Features: Spores 8-11 x 5-8 µ; ellipsoid to slightly amygdaliform; with a small pore; smooth; thick-walled; hyaline in KOH; dextrinoid. Basidioles inflated, brachybasidiole-like. Cheilocystidia to about 50 x 16 µ; lageniform, ventricose, or irregular. Pleurocystidia absent. Floccose material on cap surface composed of inflated, subglobose to pyriform elements 15-25 µ across.

REFERENCES: (Corda, 1839) Singer, 1962. (Bolton, 1788; Saccardo, 1912; H. V. Smith, 1954; Smith, Smith & Weber, 1979; H. V. Smith, 1981; H. V. Smith & Weber, 1982; Weber & Smith, 1985; Arora, 1986; Phillips, 1991/2005; Lincoff, 1992; Metzler & Metzler, 1992; Horn, Kay & Abel, 1993; Barron, 1999; Vellinga, 2001e; McNeil, 2006; Kuo & Methven, 2010.) I have not collected this mushroom.

Further Online Information:

Leucocoprinus birnbaumii at MykoWeb
Leucocoprinus birnbaumii at Roger's Mushrooms


The photos below were sent in by readers whose flower pots produced Leucocoprinus birnbaumii:

Leucocoprinus birnbaumii

Leucocoprinus birnbaumii

Leucocoprinus birnbaumii

Leucocoprinus birnbaumii

Leucocoprinus birnbaumii

Leucocoprinus birnbaumii

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Cite this page as:

Kuo, M. (2015, August). Leucocoprinus birnbaumii. Retrieved from the MushroomExpert.Com Web site: