Haymaker's Mushroom
Panaeolina foenisecii
Also called lawn mower's mushroom, brown mottlegill, haymaker's panaeolus
A tiny, extremely common lawn fungus with a hygrophanous date-brown cap that dries pale from the centre, and mottled dark brown gills with pale edges. Its dark brown rather than black spore print separates it from true Panaeolus.
Overview
The Haymaker's Mushroom (Panaeolina foenisecii) is probably the most abundant small brown mushroom on mown grass in the temperate world. The species name means of the haymaking, referring to its appearance in early summer when grass is cut. It is small, unremarkable at a glance, and present in almost every lawn that has seen rain.
Its identity rests on a few reliable features: a strongly hygrophanous cap that changes colour dramatically as it dries, gills that are mottled or blotchy because the spores ripen unevenly across each gill face, and a dark brown spore deposit. The mottling is shared with the dung-loving Panaeolus species, but those give a jet-black print with smooth spores, while Panaeolina has roughened, warted spores and a warmer dark brown deposit — the character on which the genus was separated.
The drying pattern is worth watching for. A moist cap is a rich dark date-brown; as it loses water it pales from the centre outwards, and for a while a distinct two-tone banded appearance is visible with a dark outer zone and a pale disc.
How to identify it
Cap
1 to 3 cm across, hemispherical to conical at first, expanding to convex or broadly bell-shaped, sometimes with a very low umbo. The surface is smooth, dry to slightly velvety, and strongly hygrophanous: dark date-brown or reddish-brown when moist, drying to pale tan or greyish-buff from the centre, frequently showing a darker marginal band during the transition. The margin may be faintly translucent-striate when wet.
Gills
Adnate, moderately broad and fairly well spaced, pale greyish-brown when young and maturing to dark chocolate or purplish-brown with a distinctly mottled, uneven appearance. The gill edges remain paler and finely whitish-fringed, visible with a lens.
Stipe
3 to 7 cm tall and only 1 to 3 mm thick, slender, straight and fragile, hollow, whitish to pale brown and often darker towards the base, with a faint powdery bloom near the apex. There is no ring and no volva.
Flesh & spore print
The flesh is very thin and pale brown. Odour and colour changes are negligible. The spore print is dark brown to purple-brown rather than black, and under the microscope the spores are ornamented with fine warts, a key generic character.
Where and when it grows
This is a fungus of short grass in disturbed and managed settings: garden lawns, playing fields, verges, parks, golf courses and grassy waste ground. It is far more frequent in regularly mown, moderately fertilised turf than in ancient unimproved grassland, and it appears scattered or in loose troops rather than rings.
The season is long, from late spring right through to late autumn, with fruitings appearing within a day or two of rain in warm weather. It is one of the most cosmopolitan of all agarics, common throughout Europe, North America, Asia, Australasia and beyond wherever lawns are mown.
Ecological role
Panaeolina foenisecii is saprotrophic, decomposing dead grass roots, clippings and the fine organic thatch layer in turf. It responds rapidly to moisture, producing large numbers of small short-lived fruitbodies over a day or two and then vanishing until the next rainfall, which is a typical strategy for fungi exploiting a thin, frequently refreshed nutrient layer.
The uneven ripening of spores across each gill face — visible as mottling — allows spore release to be staggered over the life of the fruitbody rather than concentrated in a single flush. Given its abundance on mown grass, it plays a meaningful part in recycling grass litter in urban and suburban green space.
Similar species
True Panaeolus species such as Panaeolus papilionaceus share the mottled gills but have a jet-black spore print, smooth spores, and often a fringe of toothy white veil fragments along the cap margin; several are strictly dung-associated rather than turf-dwelling. Panaeolus fimicola is greyer and grows on dung and manured ground.
Psathyrella species are more fragile still, with a distinctly whitish brittle stipe, a more markedly striate cap margin and a purple-black to dark purple-brown print, and their gills darken evenly rather than becoming blotchy. Conocybe species have narrow conical caps, a rusty cinnamon-brown print and even-coloured gills. Marasmius oreades on the same lawn is easily separated by its broad, distant pale gills, tough pliant stipe and white spore print.