Angel's Bonnet Identification Guide

First impressions and the setting

Angel's Bonnet is an autumn fungus of damp deciduous woodland, and you almost always meet it in the same situation: a fallen beech or ash limb, a mossy stump, or the base of a standing trunk, carrying a scatter or a loose tuft of small, pale, bell-shaped caps on wire-thin stems. From two metres away the colony reads as a haze of grey-white dots against dark bark. Get closer and the caps resolve into neat, slightly conical bonnets, one to two and a half centimetres across, sitting on stipes that catch the light with a distinctly polished, silvery sheen.

The genus is obvious at once. Mycena species are small, fragile, with a cartilaginous stipe and a conical or bell-shaped cap that is usually translucent-striate, meaning the lines of the gills show through the cap skin as fine radial grooves. The work of identification is entirely in separating this species from its many relatives, and for Angel's Bonnet the decisive characters are colour behaviour, stipe surface, substrate and odour.

Reading the cap

Start with a young specimen, because this species changes dramatically with age. A fresh cap is conical to narrowly bell-shaped, and its colour is a soft olive-grey with a definite yellowish or greenish-ochre wash, often darkest in the centre and paler toward the margin. It is hygrophanous, so a rain-soaked cap looks darker and more translucent and a drying one lightens quickly. Older caps expand to broadly convex or almost flat with a low umbo, and by then the olive tints have drained away to pale cream, ivory or greyish-white, sometimes with only a hint of yellow left at the disc.

This fading is why so many collections are misfiled. If every cap in front of you is pale, hunt for the smallest, youngest button in the group and check whether it carries the olive-yellow tone. The cap surface is smooth, faintly greasy in wet weather, matt when dry, and translucent-striate almost to the centre. The margin is thin, even, sometimes minutely scalloped in age, but never furnished with the coarse crenulate teeth that some relatives show.

Gills, stipe and base

Turn a cap over. The gills are adnate, often with a small decurrent tooth running a short way down the stipe, moderately spaced, with roughly twenty to thirty reaching the stipe plus several tiers of shorter intermediate gills. They start whitish, then pass through pale grey to greyish-cream, occasionally with the faintest flesh-coloured tint in age. The gill edges are concolorous or slightly paler and appear even under a lens rather than fringed or darkly marked.

The stipe is the second key. It is three to eight centimetres long but only one to three millimetres thick, cylindrical, hollow, brittle, and smooth to the naked eye with a slightly greasy, polished, silvery-grey look. Colour runs from whitish or pale grey at the apex through silvery grey-olive in the middle to a darker greyish-brown or slightly yellow-olive tone at the base. It is not longitudinally grooved and it does not develop the vivid orange or reddish-brown lower half that some woodland bonnets do.

At the very base, look for a small tuft of coarse, stiff white fibrils where the stipe meets the bark. Angel's Bonnet usually has this strigose collar, and it helps anchor the fungus on hard wood. Pull a fruitbody gently and it detaches with a few strands of white mycelium rather than a rooting extension.

The flesh is thin, watery grey-white, and shows no colour change when cut. There is no latex, no ring and no volva. If you break a stipe you get a clean brittle snap.

The odour test

This is the character that closes the identification. Angel's Bonnet has a nitrous, iodine-like smell, usually described as iodoform, and it is strongest as the tissue dries rather than in a wet fresh specimen. Fresh in the field, a single fruitbody may smell of almost nothing. To draw the odour out, crush two or three caps and stipes between your fingers and hold them cupped in a warm palm for a minute, or seal a small collection in a pot or a paper packet for ten to twenty minutes and then open it under your nose. The sharp, penetrating chemical note that comes off is unmistakable once learned, and it is worth practising on a known collection.

Taking a spore print

A print is straightforward if you are patient with such a small mushroom. Cut the stipe flush with the gills, set the cap gill-side down on a piece of card that is half black and half white, cover it with an upturned cup or a small container to keep the humidity up, and leave it for four to eight hours in a cool place. Because the cap is tiny and thin, it dries out fast; a droplet of water on the cap surface or a damp tissue inside the container helps.

The deposit is white, and against black card it shows as a faint pale bloom in the shape of the gill pattern. That white print rules out several superficially similar small woodland species with brown, pink or dark spores. Under a microscope the spores are elliptical, smooth, and turn blue-black in Melzer's reagent, which is a genus-level confirmation rather than a species one.

Substrate and season

Angel's Bonnet is a wood decayer of broadleaved trees. Beech is the classic host, with ash, hazel, sycamore, elder, oak and various shrubs also regularly recorded. It fruits on fallen branches, stumps, cut ends, exposed roots and the bark of standing trunks, often in the mossy zone near ground level, and it can appear on well-rotted twiggy debris buried in leaf litter. Fruitbodies come singly, in scattered troops or in small loose clusters, but rarely in the dense multi-stemmed bundles typical of some relatives.

The season is firmly autumnal, from early September through to the first hard frosts, peaking in cool damp weather in October and November. It is a fungus of humid, sheltered woodland rather than exposed grassland.

Separating it from look-alikes on morphology alone

Mycena inclinata is the closest trap. It is larger and more robust, grows in dense tufts almost exclusively on oak and sweet chestnut, has a cap margin decorated with distinct crenulate teeth or scallops, and develops a striking two-tone stipe that is whitish above and bright yellow-orange to reddish-brown below. Its odour is nitrous but coarser.

Mycena galericulata is bigger again, tougher, with a strongly grooved bell-shaped grey-brown cap, gills that acquire an obvious pink flush and are joined by cross-veins, a long rooting stipe base, and no iodoform odour.

Mycena polygramma has a stiff, silvery stipe that is clearly grooved lengthwise under a lens, a greyer cap without olive tones, and no distinctive smell.

Mycena vitilis grows from buried twigs in litter rather than on visible wood, has a tough, elastic, deeply rooting stipe and a plain grey cap.

Mycena olivaceomarginata shares an olive tint but lives in grassland, is smaller, and has gill edges marked with a distinct olive-brown line visible with a lens.

Mycena maculata develops reddish-brown spots on cap and gills with age and clusters on conifer or hardwood stumps.

Work the sequence in this order and you rarely go wrong: broadleaf wood, small bell cap with olive-yellow tints fading to cream, translucent striations, smooth polished silvery-olive stipe with white basal fibrils, white spore print, iodoform odour on drying.