Milking Bonnet

The Milking Bonnet is one of the most abundant small fungi of the temperate woodland floor, and one of very few Mycena species that can be named on a single unambiguous character: break the stem and a drop of opaque white liquid appears at the fracture.

It fruits in large numbers among fallen leaves, needles, twigs and moss, often carpeting a patch of woodland floor. Colour forms have caused endless confusion — the typical form is grey-brown, var. nigra (often treated as Mycena leucogala) is almost black, and var. candida is pure white — but all release the same white latex.

As a member of Mycena in the family Mycenaceae, it has the standard bonnet architecture: a small conical to bell-shaped, radially grooved cap, a very slender hollow stem, white to greyish adnate gills and a white spore print.

Cap

0.8–2.5 cm across, conical to bell-shaped, sometimes expanding to broadly campanulate with a small umbo. Grey-brown to mouse-grey, darker at the centre and paler toward the margin; blackish-grey in the dark form and pure white in the pale form. The surface is dry to slightly greasy and deeply marked with translucent radial lines and shallow grooves that reach almost to the centre when moist.

Gills

Adnate, sometimes with a short decurrent tooth, moderately spaced, fairly narrow to moderately broad, white to pale grey, with even, concolorous edges. Short intermediate gills are present.

Stipe

3–8 cm long and only about 1–2 mm thick, cylindrical, hollow, very slender and fragile, smooth or minutely powdered above and grey to grey-brown (blackish or white in the colour forms), with the base conspicuously covered in coarse white woolly hairs.

Latex, flesh and spore print

Snapping the stem, especially near the base, releases a drop of opaque white latex — the essential character. It flows most freely in fresh, well-hydrated fruitbodies. The flesh is thin and pale with no strong odour, and the spore print is white.

It grows in leaf litter, needle beds, moss, small twigs and woody debris in broadleaf, coniferous and mixed woodland, and also in hedge bottoms, scrub, heathland and grassy places with plant litter. It has no tree preference and is equally at home under beech, oak, birch, pine and spruce.

Fruitbodies appear scattered or in large troops, often in the hundreds, and the species is common and widespread throughout temperate Europe, Asia and North America. The season is long, running from summer through autumn and often into early winter until hard frosts arrive.

Mycena galopus is a litter saprotroph and is one of the most studied fungi in this role, because its mycelium is a major agent in the early decomposition of leaf litter in temperate forests. It degrades both cellulose and lignin in fallen leaves, needles and small twigs, initiating the transformation of litter into humus.

The mycelium is diffuse and permeates the litter layer rather than concentrating in a single substrate pocket, which is why fruitbodies come up in wide scattered troops rather than tufts. Wind moves the white spores at ground level, and the extended fruiting season lets it release spores over many months.

The Bleeding Bonnet (Mycena sanguinolenta) is the same size and shape but exudes dark reddish-brown latex and has a distinct reddish-brown gill edge visible with a lens. Mycena haematopus releases dark blood-red latex and grows in tufts on dead wood rather than in litter, with a scalloped cap margin.

Mycena leucogala is the blackish form of the Milking Bonnet itself and shares the white latex. Other small grey bonnets such as Mycena filopes and Mycena metata have no latex at all — the single most useful check — while Mycena polygramma is larger with a silvery, longitudinally grooved stem. Small white bonnets like Mycena flavoalba also lack latex and have a paler, yellowish-tinged cap.