Lilac Bonnet

The Lilac Bonnet is among the most frequently recorded species of Mycena in temperate woodland, and one of the largest and most robust of the genus. Where most bonnets are frail things a centimetre or two across, this species reaches a size and firmness that leads many people to look for it in other genera entirely.

It is a litter fungus rather than a wood fungus, fruiting singly or in scattered troops among fallen leaves and needles. Its colour is famously variable: typical fruitbodies are lilac to violet, but pink, rose, pale mauve, greyish, brownish and near-white forms are all common, and several have been treated as separate varieties.

The reliable characters are structural rather than chromatic — broad, widely spaced, strongly interveined gills with a decurrent tooth, a smooth polished stem with a woolly base, a white spore print, and a strong smell of raw radish or turnip that is released when the flesh is crushed.

Cap

2–5 cm across, conical or bell-shaped at first, expanding to broadly convex or almost flat with a low umbo. Lilac, violet, rose-pink, mauve, greyish-lilac or nearly white; hygrophanous, fading as it dries and usually palest at the margin. The surface is smooth and slightly greasy when wet, and translucent radial lines mark the margin over the gills beneath.

Gills

Broad, rather thick and distinctly widely spaced, adnate with a short decurrent tooth, and connected by conspicuous cross-veins on the faces. White to pale lilac or pinkish, with paler, even edges, and often flushed with the cap colour near the margin.

Stipe

3–9 cm long, 3–8 mm thick, cylindrical, hollow and fairly firm, smooth and polished above, concolorous with the cap or paler. The base is swollen slightly and covered with coarse white woolly fibrils that bind fragments of litter.

Flesh, odour and spore print

Flesh is thin, pale and watery, with a strong smell of raw radish or turnip when crushed. There is no latex and no colour change on cutting. The spore print is white.

It fruits from leaf and needle litter, moss and humus in broadleaf, coniferous and mixed woodland, and occasionally in hedgerows, parkland and well-wooded gardens. It is not fussy about host trees, appearing under beech, oak, birch, hazel, pine and spruce alike, and tolerates a wide range of soil types, including calcareous ground.

The species is common and widespread throughout temperate Europe, Asia and North America, and has been recorded from parts of the southern hemisphere. Fruiting typically begins in summer and continues through to late autumn, with the heaviest flushes after prolonged wet weather.

Mycena pura is a saprotroph of the forest floor, decomposing fallen leaves, needles, small twigs and buried plant fragments. Its mycelium permeates the litter layer, breaking down cellulose and lignin and helping to convert the annual leaf fall into humus.

Because it is not tied to a mycorrhizal partner, it can fruit in almost any woodland where litter accumulates, and it often appears in disturbed or planted woodland where more specialised fungi are absent. Spores released from the widely spaced gills are wind-dispersed at ground level, and fruiting is triggered chiefly by soil moisture and temperature rather than by the state of any particular host tree.

The Rosy Bonnet (Mycena rosea) is the closest relative: it is larger and stouter, more evenly rose-pink to pale pink rather than lilac, with a paler stem and a more strongly umbonate cap, though it shares the radish odour. Mycena diosma is darker, more greyish-violet and has a complex odour with a second component beyond the radish note.

The Amethyst Deceiver (Laccaria amethystina) can look similar in colour but has thick, waxy, deep violet gills that are far more widely spaced and coarse, a fibrous twisted stem, and a white but very warty-spored print; its whole texture is tough rather than fragile. Small Lepista species share purple tones but have crowded gills and a pale pinkish spore print, and Collybia-type mushrooms lack both the striate cap margin and the radish smell.