Beautiful Bonnet

Mycena renati is one of the prettiest of the wood-inhabiting bonnets, earning its English name from the clean contrast between a soft honey- or ochre-tinted cap and a stipe washed in bright chrome- to lemon-yellow, strongest towards the base. In good light a tuft of fresh fruit bodies on a mossy beech log is genuinely eye-catching.

The species fruits in small clustered tufts from the cut surfaces, cracks and bark edges of dead hardwood, most reliably beech. It has a fairly long season, appearing from late spring onwards rather than being restricted to the autumn peak, which makes it a useful early-season find.

A supporting character is the smell, usually described as nitrous or slightly chemical, apparent when a fruit body is crushed. Combined with the yellow stipe and the beech substrate, this makes M. renati one of the more confidently identified members of a genus notorious for requiring a microscope.

Cap

The cap is 1–3 cm across, conical to bell-shaped, later broadly convex with a small umbo. The surface is smooth, moist and translucent-striate towards the margin. Colour is pale honey, ochre-brown or yellowish-buff, often with a slightly darker, more brownish centre and a paler, sometimes almost whitish, margin.

Gills

Gills are adnate to narrowly adnexed, moderately crowded, white to pale cream, sometimes flushing very faintly pinkish with age. The edges are concolorous and lack any dark or contrasting line.

Stipe

The stipe is 3–7 cm tall and 1–3 mm thick, hollow and smooth, and is the diagnostic feature: bright chrome-yellow to lemon-yellow, most saturated in the lower half and at the base, paling towards the apex. The base is fringed with coarse yellowish to whitish hairs that bind it to the wood, and several stipes commonly arise from a shared point.

Flesh & spore print

The flesh is thin and pallid, with a nitrous or faintly chemical smell when crushed. The spore print is white; spores are smooth, ellipsoid and amyloid.

Beautiful Bonnet fruits on dead hardwood — fallen trunks, cut stump surfaces, large branches and worked timber lying in woodland. Beech is the classic host, and the species is a familiar sight on decorticated beech logs, but it also occurs on oak, hornbeam, ash and other broadleaf wood.

Small tufts emerge from cracks, cut ends and the exposed sapwood of well-rotted material, often on the shaded, damp underside of a log. The season is long, running from May or June through to October, with the best fruiting in warm, wet summer spells. It is widespread across temperate Europe and recorded from temperate Asia and North America.

Mycena renati is a wood saprotroph causing white rot in dead broadleaf timber. Its mycelium colonises the sapwood and outer heartwood of logs and stumps, degrading lignin and cellulose in the mid stages of decay, after bark-inhabiting pioneers and alongside other small agarics.

The clustered fruiting habit reflects the way the mycelium exploits localised nutrient-rich zones such as cut faces and cracks. Because it fruits well outside autumn, it exploits summer humidity in shaded woodland, and a well-colonised log may produce successive tufts across several months and several seasons before the wood is exhausted.

Mycena epipterygia also has a yellow stipe but that stipe is covered in a distinctly slimy, elastic, peelable skin, and the cap is greyish-yellow with a separable gelatinous pellicle; it fruits in litter and moss rather than in tufts on hardwood logs. Mycena flavescens is paler and more slender with a litter habitat.

Mycena galericulata shares the tufted hardwood habit but has a plain grey-brown cap, a grey stipe with no yellow, and gills that flush pink. Mycena inclinata is separated by its scalloped cap margin, orange-brown lower stipe and preference for oak. The clean chrome-yellow, non-slimy stipe with a pale honey cap on beech is the combination that points to M. renati.