Panaeolina foenisecii — Lawnmower's mushroom, haymaker's mushroom

Lawnmower's mushroom

Lawnmower's mushroom2, photograph by David Carmean.

Lawnmower's mushroom

Lawnmower's mushroom2, cap margins changed from brown to buff with loss of water, photograph by Ludovic Le Renard.

Lawnmower's mushroom

Lawnmower's mushroom10, sketch by Oluna Ceska showing the habit, warty spores with a small pore at one end, and the elongate or bottle-shaped sterile cells that give gill edges their light colour.

Odour: Indistinct.
Cap: 1–3 cm in diameter, hemispherical to conical when young, later more flattened, but often with a low central bump. The colour changes as the cap dries. When wet, the surface is completely brown or orange brown. As they dry, caps often develop a dark brown band around the margin, then a light band, then an orangish-brown central disc. After losing more water, caps become light beige, orangish in the centre. The cap surface is matte, not shiny.
Gills: Broadly to narrowly attached, moderately close. The colour is initially light brown, then mottled brown (see Additional Images), then brown. The spores ripen in patches and the dark brown colour of the ripest ones causes the mottling. Gill edges remain lighter than sides of gills (see Additional Images).
Stem: 3–9 cm long x 0.2–0.4 cm wide, fibrous, roughly equal in diameter from top to bottom. Colour is whitish to tan, darker where handled.
Ring or veil: None.
Cup: None.
Spores: 11–18 x 6–9 µm, almond-shaped, dark brown, with a subtly roughened surface.
Habitat: In lawns, on woodchips, in forests; saprotrophic.
Geographical distribution: Common, especially in well-watered lawns in summer, throughout North America and Europe.

Small brown mushroom are difficult to identify. While the lawnmower's mushroom is not highly toxic, some of its look-alikes are dangerous if eaten, especially to children and pets. Look-alikes include hallucinogenic mushrooms that can be recognized by their darker spore colours–black in Panaeolus species; dark purplish brown in Psilocybe species; and by the bases of their stems, which in the hallucinogenic species often bruise blue. Most species of hallucinogenic mushrooms have smooth spore walls rather than subtly roughened walls like the lawnmower's mushroom (see Additional images) but verifying wall ornamentation requires careful, high-magnification microscopy.

If the spore print is rusty brown or cinnamon brown and if a ring is present around the stem, the mushroom may be one of the Galerina or Conocybe species that contain potent, liver-destroying amatoxins. Lack of a ring around the stem is inconclusive, however, because rings may be fragile, present when mushrooms are young and disappearing with age. Spores are somewhat smaller (7.5 to 10.5 (13) x 4.5 to 6.5 (7) µm in two toxic species, Galerina marginata and Conocybe filaris compared with the lawnmower's mushroom. Spore walls are smooth in the Conocybe but Galerina marginata, like the lawnmower's mushroom, has slightly roughened spore walls5,6.

Panaeolus cinctulus, the belted panaeolus is similar to the lawnmower's mushroom but has black rather than dark brown spores. Spores of the belted panaeolus are smooth-walled.

Lawnmower's mushrooms are common in lawns and so they are among the most frequent mushrooms nibbled by young children. Eating five or fewer lawnmower's mushrooms that were later carefully identified did not cause significant illness in children in Germany and Switzerland7.

Toxins: Carefully identified lawnmower's mushrooms in the Pacific northwest did not contain detectable levels of the hallucinogen psilocybin8. Reports that the species sometimes does contain hallucinogens have not been confirmed7.

Symptoms: In North America, lawnmower's mushrooms have been blamed for gastrointestinal upsets or central nervous system symptoms including hallucinations and disorientation9 but it is likely that the mushrooms causing the symptoms were misidentified and other species of small brown mushrooms were responsible for the illness.

Treatment: Contact your regional Poison Control Centre if children or pets have eaten any small brown mushrooms, or if someone you know becomes ill after consuming mushrooms like these. Poison centres provide free, expert medical advice 24 hours a day, seven days a week. If possible, save the mushrooms or some of the leftover food containing the mushrooms to help confirm identification.

Poison Control:
British Columbia: 604-682-5050 or 1-800-567-8911.
United States (WA, OR, ID): 1-800-222-1222.

MyCoPortal. Mycology Collections Portal, <> accessed March 2018.

Specimen Panaeolina foenisecii UBC F29248, GenBank #not available.

Siegel, N. & Schwarz, C. Mushrooms of the Redwood Coast. A Comprehensive Guide to the Fungi of Coastal Northern California. Ten Speed Press, Berkeley, California (2016).

Trudell, S., Ammirati, J. F. & Mello, M. Mushrooms of the Pacific Northwest. Timber Press, Portland, Oregon (2009).

Gulden, G. Galerina Earl Pp. 785-804 in Funga Nordica, Agaricoid, Boletoid and Cyphelloid Genera (eds. Knudsen, H. & Vesteroholt, J.) Nordsvamp, Copenhagen, Denmark (2008).

Hausknecht, A. & Vesterholt, J. Pholiotina Fayod Pp. 651-657 in Funga Nordica, Agaricoid, Boletoid and Cyphelloid Genera (eds. Knudsen, H. & Vesterholt, J.) Nordsvamp, Copenhagen (2008).

Schenk-Jaeger, K. M. et al. No clinically relevant effects in children after accidental ingestion of Panaeolina foenisecii (lawnmower's mushroom). Clin Toxicol (Phila) 55, 217-220, doi:10.1080/15563650.2016.1271129 (2017).

Beug, M. W. & Bigwood, J. Psilocybin and psilocin levels in 20 species from 7 genera of wild mushrooms in the Pacific northwest, USA. J. Ethnopharmacol. 5, 271-285, doi:10.1016/0378-8741(82)90013-7 (1982).

Beug, M. W., Shaw, M. & Cochran, K. W. Thirty-plus years of mushroom poisoning: Summary of the approximately 2,000 reports in the NAMA case registry. McIlvainea 16, 47-68 (2006).

Panaeolina foenisecii UBC F26637.