Blackedge Bonnet Identification Guide

Where You Are Standing

The classic encounter is in beech woodland on chalk or limestone, in autumn, on a deep bed of leaf litter with very little ground vegetation. Blackedge Bonnet fruits in troops, sometimes scattered over several square metres, and the general impression from standing height is of a colony of dull pinkish-lilac to greyish-brown caps on slender stems, each 3-8 cm tall, pushing up through the leaves. Nothing about that first impression is diagnostic; a dozen litter species look like it. The identification is made by crouching down, picking one, and turning it over.

The Gill Edge, and Why It Comes First

Normally you work cap, then gills, then stipe. With this species it is worth inverting the order, because the gill edge is the character that resolves everything else. Hold a mature fruit body so light falls across the gill face and look at the free margin of each gill, ideally with a hand lens. The gill face is pale lilac, pinkish-grey or dull violaceous, and the extreme edge is finished with a distinct dark line, purple-black to blackish-brown, as though someone had run a fine pen along every gill. It is visible to the naked eye on a good specimen and unmistakable at 10x.

Two practical points. Very young buttons may show the edge only weakly, so choose a fully expanded cap. And in badly faded or waterlogged old specimens the pigment can wash out, so check several individuals from the troop rather than trusting one. If you have a microscope, the edge is packed with cheilocystidia loaded with brown-violet vacuolar pigment, which is exactly what produces the visible line.

Reading the Cap

Cap 2-5 cm across, which makes this one of the larger bonnets. It starts conical to convex with a slightly inrolled edge, then expands to broadly convex or almost flat, often keeping a low central umbo. The surface is smooth, slightly greasy when wet and hygrophanous, drying paler and duller from the centre outwards. Colour runs from purplish-brown or lilac-brown when fresh and moist through pinkish-grey to dingy pale buff as it dries. The margin is finely lined or translucent-striate when damp, and the striations correspond to the gills beneath.

Gill Attachment and Spacing

Beyond the dark edge, note that the gills are adnate to slightly emarginate, moderately spaced rather than crowded, fairly broad, and interspersed with shorter gills that do not reach the stem. They are not decurrent. That last point matters when separating some of the look-alikes below.

Stipe, Base and Flesh

The stipe is slender, 3-8 cm long and only 2-5 mm thick, cylindrical, hollow, smooth or very finely fibrillose, and coloured like a paler washed-out version of the cap: pale lilac, greyish-violet or brownish. Near the base it is often slightly darker and finely hairy, and a small pad of white mycelial down usually binds a plug of leaf fragments. Pull the specimen up rather than snapping it off, or you will lose that base detail.

The flesh is thin, watery, and pale with a faint violet tinge in the stipe cortex. Cut lengthwise and note that there is no latex and no significant colour change. Crush a piece of stipe between your fingers and smell it: the strong raphanoid, radish-like odour is a solid supporting character for the whole Mycena pura group and helps confirm you are in the right neighbourhood before you make the final call on the gill edge.

Getting a Spore Print

Cut the stipe flush with the gills, set the cap gill-side down on black card or dark glass, cover it with a glass or a bowl and leave it three to four hours or overnight. The deposit is white. It is a modest quantity because the fruit body is small, so use a dark background and good light to read it. If you have iodine reagent, the spores are amyloid, staining blue-grey, which is a genus-level confirmation rather than a species one.

Substrate, Season and Habitat Preferences

Blackedge Bonnet is a litter decomposer, not a wood rotter and not mycorrhizal. It fruits from deep accumulations of broadleaf leaf litter, overwhelmingly beech, and it shows a marked preference for base-rich, calcareous soils. Look on the litter-filled hollows of beech hangers, along the leeward side of banks where leaves pile deep, and under mature standards where the litter layer has been building for years. Fruiting runs from late summer through autumn, often continuing later than many woodland species. Troops are usually large; a single isolated fruit body is worth double-checking.

Separating It From the Look-Alikes

Mycena pura is the species most often confused with it and can be almost identical in cap colour, size, habitat and radish smell. The separation is the gill edge: in M. pura the edge is concolorous with the gill face, showing no dark line at any magnification. Check several specimens before concluding either way, and take the check seriously, because colour and stature overlap far too much to decide any other way in the field.

Mycena rosea is generally larger and stouter, with a distinctly pink to rose cap and a whitish or pale pink stipe, and again shows no dark gill edge.

Mycena pearsoniana carries violet tones and a similar smell but has gills that are more clearly decurrent by a tooth and lacks the dark margin.

Mycena diosma shares the lilac-grey tones and has a more complex aromatic smell, but the gill edges are not blackened.

Laccaria amethystina can be a distant confusion in the same litter, but it is uniformly deep violet including the gills, has thick, widely spaced, waxy-looking gills, a fibrous twisted stipe and, decisively, a white spore print made of spiny globose spores rather than smooth amyloid ones.

Small Inocybe and Entoloma species in litter may share the dull brownish-lilac look, but Inocybe drops a brown print and Entoloma a pink one, so a print resolves them immediately.

Field Sequence

Beech litter on chalk, troops of pinkish-lilac caps, striate margin, adnate moderately spaced pale lilac gills, dark purple-black gill edges under a lens, slender hollow pale lilac stipe with a hairy white base pad, radish smell, white spore print. When those line up, Blackedge Bonnet is one of the more comfortable Mycena identifications you can make without a microscope.