Bearded Fieldcap

The Bearded Fieldcap, Agrocybe molesta, is a fleshy, pale grassland mushroom that appears mainly in late spring and early summer, well ahead of the main autumn fungal season. It has long been known as Agrocybe dura, and both names appear in the literature for the same fungus.

Agrocybe belongs to the Bolbitiaceae and gathers the fieldcaps: medium-sized, dull brown to cream mushrooms with brown spore prints, adnate gills and, in several species, a ring on the stipe. Compared with the delicate conecaps in the same family, fieldcaps are firm and substantial, with caps that can hold their shape for several days.

This species is recognised by its whitish to pale cream cap, which characteristically cracks into irregular plates in dry sunny weather, and by the whitish veil fragments that hang like a torn fringe or beard from the cap margin.

Cap

The cap is 4 to 10 cm across, convex then flattening, sometimes with a low broad umbo, and firm-fleshed. The surface is dry, smooth and matt, whitish, ivory or pale cream, ageing to dull buff or with faint ochre tones over the disc. In dry weather it frequently cracks into coarse angular patches, and shreds of the white partial veil often hang from the incurved margin, giving the shaggy bearded fringe of the English name.

Gills

Gills are adnate to adnexed, sometimes with a short decurrent tooth, moderately close and broad. They begin pale grey-buff or whitish, then colour through clay-brown to dull snuff-brown or cigar-brown as the spores ripen. The edges stay narrowly whitish.

Stipe

The stipe is 4 to 9 cm long and 5 to 12 mm thick, firm, whitish to cream, usually more or less equal but often with a slightly rooting or tapering base that runs down into the soil. A thin, fragile ring or ring zone may be present near the top, but it is easily lost, and the stipe surface below is finely fibrillose. There is no volva.

Flesh and spore print

The flesh is white, firm and comparatively thick for the family, unchanging or only faintly browning when cut. The spore print is dull brown to snuff-brown, and the smooth ellipsoid spores have a distinct germ pore, as in other Agrocybe species.

This fieldcap grows in grassy and disturbed ground: lawns, roadside verges, park grass, field margins, dune grassland, gardens, waste ground and the edges of arable fields, and it also turns up on mulched borders. It favours open, well-drained, often calcareous or nutrient-enriched soil in full sun.

Fruiting is notably early in the year, chiefly from late spring into early summer, with occasional later appearances after wet spells. Fruit bodies are usually scattered or in small groups, sometimes forming loose arcs where the mycelium has spread outward. The species is common through Europe and is recorded across temperate North America and other temperate regions.

Agrocybe molesta is saprotrophic, breaking down buried plant remains, grass roots, thatch and humus in the topsoil. It forms no mycorrhizal association with trees or grasses, and its fruit bodies frequently arise from a slightly rooting base connected to decaying organic matter below the surface.

Its early-season fruiting reflects a mycelium that can exploit spring soil moisture and rising temperatures before the main autumn flush of grassland fungi. The firm, thick flesh allows fruit bodies to persist for several days in dry sunny conditions, though it is that same drying that causes the characteristic cracking of the cap surface. Spores are wind-dispersed once the gills darken.

Agrocybe praecox, the Spring Fieldcap, appears at the same season but is warmer tan to ochre-brown rather than ivory, has a better-developed persistent membranous ring, and usually grows on mulch or in shrubberies with a more clearly rooting base. Agrocybe pediades, the Common Fieldcap, is much smaller with a smooth ochre-yellow cap and no veil fringe. Agrocybe rivulosa is larger and paler with a strongly wrinkled cap and a prominent ring, and grows almost exclusively on wood chip.

White Agaricus species in grass can look similar at a distance but have free gills that pass through pink to chocolate brown and a dark brown print, plus a well-formed ring. Melanoleuca species in turf have white spore prints and notched gills. Species of Volvopluteus in enriched ground have a sac-like volva at the base and a pink print, neither of which occurs here.