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Panaeolus foenisecii: The Lawn Mower's Mushroom

[ Basidiomycetes > Agaricales > Bolbitiaceae > Panaeolus . . . ]

by Michael Kuo

Just about everyone has seen this mushroom at one time or another. It is one of the most common and widely distributed lawn mushrooms in North America, and it often fruits in large numbers. Some people are upset by this; I often receive e-mails from people wanting to know how Panaeolus foenesecii or some other lawn mushroom can be eradicated. I wonder whether these people would go to BaldEagleExpert.Com and ask for instructions on shooting Haliaeetus leucocephalus? Anyway, the short answer is: you can't get rid of them. If you are worried about mushrooms ruining the appearance of your lawn, I suggest you rethink your priorities in life. But if you are worried about your toddler popping a poisonous mushroom in her mouth, I salute your concern--though you're still not going to have any luck getting rid of the mushrooms. The best solution in this case is to teach your children not to eat everything they see--and if they aren't learning this lesson well, not to leave them unsupervised on your lawn in the summer.

The lawn mower's mushroom, in fact, may well be dangerous for toddlers, since it is known in some instances to contain small amounts of psilocybin. Chemical analysis has revealed this hallucinogen in some collections from some parts of North America. Elsewhere, the mushrooms appear to be inactive. But even where psilocybin does occur in the lawn mower's mushroom, it occurs in such small amounts that a thrill seeker would need to eat tons of them to be thrilled. And, anyway, eating little brown mushrooms you have compared to pictures in a field guide or on a Web site is a stupid idea in the first place!

There is a much better thing to do with the lawn mower's mushroom than try to get high from it: use it to practice your mushroom identification skills. Since it is so common and so widely distributed, it is the perfect mushroom for demonstrating a macrofeature that is often important in mushroom identification: the lawn mower's mushroom has a "hygrophanous" cap. As it loses moisture and begins to dry out, its color changes rather dramatically. The result is that one finds many specimens in the process of transforming their colors, with different tones in distinct areas.

Whether a mushroom is hygrophanous or not is sometimes a cruicial macrofeature determining its identity. In fact, a whole subgenus of Cortinarius, containing hundreds of mushrooms, is separated on the basis of hygrophanous caps (among other things). Unfortunately, mushrooms that are supposed to have hygrophanous caps do not always hold up their end of the bargain as well as the lawn mower's mushroom. And, a further problem with determining whether a mushroom is or is not hygrophanous is that you probably need to have several specimens on hand; if you have only one and it is not handily in the process of transforming itself, how would you know it was (or is about to be) hygrophanous?


Ecology: Saprobic; growing alone to gregariously on lawns, in meadows, and in other grassy areas; very common; widely distributed in North America; late spring, summer, and fall.

Cap: 1-3 cm; widely conical or bell shaped, becoming convex or nearly flat; smooth or cracked in dry weather; hygrophanous (see comments above); dark brown to cinnamon brown, changing to light brown, tan, or buff--or with bands of these shades when in the process of drying out.

Gills: Notched, attached to the stem, or pulling away from the stem; brown, becoming darker brown; sometimes with a mottled appearance; sometimes with pale edges; close.

Stem: 4-8 cm long; 1.5-4 mm thick; more or less equal; sometimes with an enlarged base; smooth; fragile; pale, becoming darker brown.

Flesh: Thin; fragile.

Spore Print: Dark brown to purple brown.

Microscopic Features: Spores 12-17 x 7-11 µ; subfusoid to lemon shaped; rugose; dextrinoid; dark reddish brown in KOH. Cheilocystidia variously shaped (subfusoid to cylindric or subcapitate); to about 50 µ long. Pleurocystidia absent, or scattered and scarcely projecting ("pseudocystidia"). Pileipellis cellular/hymeniform, with projecting pileocystidia.

Psathyrella foenesecii is the name prefered by A.H. Smith. Panaeolina foenesecii is a synonym; some mycologists separate Panaeolina from Panaeolus on the basis of roughened, rather than smooth, spores.

REFERENCES: (Persoon, 1800) Schröter, 1926. (Fries, 1821; Saccardo, 1887; Smith, 1949; Stamets, 1978; Smith, Smith & Weber, 1979; Arora, 1986; Horn, Kay & Abel, 1993; Evenson, 1997; Barron, 1999; Roody, 2003; McNeil, 2006; Miller & Miller, 2006.) Herb. Kuo 05179501, 06160211, 10040512, 05050601.

Further Online Information:

Panaeolus foenisecii at MykoWeb
Panaeolina foenisecii at Roger's Mushrooms


Panaeolus foenisecii

Panaeolus foenisecii

Panaeolus foenisecii

Panaeolus foenisecii

Panaeolus foenisecii
Pileipellis, pileocystidium

Panaeolus foenisecii

Cite this page as:

Kuo, M. (2002, June). Panaeolus foenisecii: The lawn mower's mushroom. Retrieved from the MushroomExpert.Com Web site:

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