Deadly Galerina

The Deadly Galerina is a small, drab, brown mushroom that fruits in scattered troops or loose clusters on rotting wood. It belongs to Galerina, a large genus of little brown mushrooms in the Hymenogastraceae, most of which grow among moss and are separated only microscopically. G. marginata is one of the larger and more distinctive members, and the mushroom formerly called G. autumnalis is now treated as the same species.

What distinguishes it within its genus is the combination of a ring on the stem, a wood-inhabiting habit, and a hygrophanous cap that changes colour dramatically as it loses moisture — dark tawny or date-brown when damp, drying pale ochre or buff from the centre outward, so a single log may carry caps of three different shades at once.

Because it is small, brown, and shares its habitat with a number of similar wood-dwelling species, careful attention to the ring, the stem surface below the ring, and the spore print colour is what makes a confident identification possible.

Cap

The cap is 1.5–6 cm across, convex to bell-shaped at first and expanding to nearly flat, often with a low broad umbo and a faintly striate margin when moist. It is smooth, slightly sticky in wet weather, and strongly hygrophanous: tawny brown, date-brown or ochre-brown when damp, fading to dull yellow-buff or pale tan as it dries, usually from the centre outward so a two-toned zonation appears.

Gills

Gills are adnate to slightly decurrent with a tooth, moderately crowded, and narrow. They are pale yellowish-brown or tan when young, darkening with maturity to rusty brown as the spores ripen, and the gill faces often become dusted with rusty spore deposit.

Stipe

The stem is 2–8 cm long and 2–8 mm thick, roughly equal or slightly swollen at the base, and pale brown above the ring, darkening to dark brown or nearly blackish-brown toward the base with age. It carries a thin, membranous ring in the upper part, which may collapse against the stem or be dusted rusty by falling spores; below the ring the surface is silky-fibrillose or faintly white-streaked but never covered in coarse recurved scales.

Flesh & spore print

Flesh is thin, pale brown and watery, with a faint farinaceous odour. The spore print is rusty brown to snuff-brown; under the microscope the spores are ornamented, warty-roughened and ellipsoid with a smooth plage.

It grows on well-rotted wood, most typically on conifer logs, stumps and buried woody debris, but also on hardwood, on wood chips, on sawdust piles and occasionally from soil rich in buried wood. Fruiting bodies appear scattered, in small troops, or in loose clusters of a few stems, rather than in the very dense fused tufts characteristic of some stump-dwelling species.

It is common and widespread throughout the temperate northern hemisphere — across Europe, northern Asia and North America — and there are records from Australia. The main season is late summer through late autumn, extending into early winter in mild regions, and it is one of the fungi still fruiting after the first frosts.

Galerina marginata is a saprophyte causing a brown rot of decaying wood. Its mycelium breaks down the cellulose of already well-decayed logs and stumps, leaving darkened, crumbly, cubically cracking residue, which places it in the later stages of the wood decomposition sequence rather than among the pioneer colonisers of freshly fallen timber.

Ecologically it is a recycler working on the final fraction of woody debris, returning nutrients from soft, punky logs to the forest floor. Its tolerance of cold extends its fruiting well past that of most autumn agarics, and its ability to colonise wood chips and sawdust means it turns up readily in managed landscapes such as parks, gardens and forestry tracks as well as in natural woodland.

Sheathed Woodtuft (Kuehneromyces mutabilis) is the closest match in size, colour, hygrophanous two-toned cap and rusty-brown spore print, and it grows in the same clustered manner on stumps. The separating feature is the stem below the ring: in Kuehneromyces it is conspicuously covered in dark, recurved, pointed scales down to the base, while in Galerina marginata it is smooth to silky-fibrillose with only faint pale streaking.

Velvet Shank (Flammulina velutipes) shares the wood habit and winter fruiting but has a viscid orange-tan cap, no ring at all, a dark velvety-brown stem base, and a white spore print. Sulphur Tuft (Hypholoma fasciculare) forms far denser fused clusters, is sulphur-yellow with greenish-tinted gills, has only a faint fibrillose ring zone, and gives a purple-brown print. Pholiota species are generally larger, with viscid, coarsely scaly caps and scaly stems, and brighter yellow to rust tones.