Clustered Brittlestem Identification Guide

First Impressions

You usually notice the arrangement before the mushroom. On bare compacted soil at the side of a path, a grassy woodland ride, a lawn edge or the shaded ground under a hedge, a tight bouquet of small brown caps stands up on a mass of pale, hair-thin stalks that all converge into a single point at ground level. The cluster can hold anything from a dozen to fifty or more individual fruit bodies, and pulled up carefully the whole bundle comes away as one unit, fused at the base into a rooting plug. That fused, many-legged base is what the species epithet describes and it is the single most useful character in the field. The mushrooms themselves are small and fragile, and the entire cluster wilts within a day or two, so most encounters are with fresh material after rain.

Reading the Cap

Individual caps are 1-3 cm across, occasionally to 4. They start narrowly conical to bell-shaped, then expand to broadly conical or convex, and the oldest may flatten with a low umbo, but they never open wide and flat like a field mushroom. When moist the colour is a warm date-brown to reddish-brown or dark clay-brown, and the cap is markedly hygrophanous: as it dries it pales dramatically from the centre outward to a dull ochre-buff, pale tan or almost greyish cream, so that a single cluster in changeable weather shows caps in every shade at once. Do not treat colour as fixed. Along the margin of young caps a lens picks up fine, whitish, cottony fibrils, the last remains of a delicate partial veil, and the moist margin is faintly translucent-striate for a few millimetres where the gills show through. The surface is dry to the touch, never slimy, and the flesh of the cap is so thin you can almost see through it when held to the light.

The Gills

Gills are adnate to narrowly attached, crowded and rather narrow, and their colour changes as the spores mature, which is the second thing to check. Young gills are pale greyish or clay-buff; they darken to grey-brown, then to a deep purplish grey-brown or nearly blackish brown at maturity. Under a lens the gill edges look finely white-fringed, a pale line against the dark faces, and this contrast is often visible with the naked eye in good light. The gills do not liquefy into black ink, and this is worth confirming on an old specimen, because it separates the brittlestems from the true inkcaps that share their habit.

Stipe, Base and Flesh

The stalks are the giveaway. Each is only 1-2 mm thick and up to 6-10 cm long, whitish to pale cream, silky-fibrillose, hollow, and remarkably brittle: attempt to bend one and it snaps rather than folding, which is precisely what the name brittlestem records. Toward the base the stalks darken slightly and become finely downy, and there they fuse with all the others into a dense, tapering, root-like common base buried in the soil. Sometimes a fine white mycelial felt and a few soil-bound strands cling to that plug. There is no ring, no volva, no bulb, and no slime layer. The flesh throughout is thin, watery brown when wet and pallid when dry, with no distinctive smell and no colour change when cut or bruised. Nothing turns blue, red, or black on handling.

Taking a Spore Print

A spore print is quick and decisive for this group. Snap off two or three of the larger caps, lay them gills-down on white paper or, better, on a card that is half white and half black, cover them with a glass, and leave them one to three hours; small, thin caps deposit fast. The print is dark: purplish grey-brown to blackish brown, never rusty, never pink, never white. Read it on the white half for hue and on the black half for density. Under the microscope the spores are smooth, ellipsoid, roughly 7-9 by 4-5 micrometres, dark brown in water, and each carries a distinct germ pore at the narrow end. The cap cuticle is cellular, built of rounded inflated cells rather than lying hyphae, which is the microscopic signature of the whole genus.

Substrate and Season

This is a saprotrophic species living on buried woody debris, root fragments and humus-rich disturbed ground rather than on standing logs. In practice that means path edges, roadside verges, park lawns, garden borders, hedge bottoms, the trampled ground beside benches and gates, and the litter of broadleaved woodland. It prefers damp, shaded, nitrogen-rich soil and appears in flushes a few days after rain, mainly from late summer through autumn, with occasional spring and mild-winter appearances in oceanic climates. The same spot often produces cluster after cluster in successive years because the underlying wood supply persists.

Separating It from Look-Alikes

The fused, many-stemmed bundle narrows the field enormously, but several species come close. Psathyrella piluliformis grows in large tufts as well, but its clusters sit directly on stumps and buried hardwood, the caps are larger, fleshier and more evenly red-brown, the stalks are thicker, and the tufts are clumped rather than fused into one narrow rooting plug. Psathyrella candolleana has a paler, honey to whitish cap with a shaggy veil-fringed margin, thicker stalks, and clusters that are loose and grouped rather than bundled from a single point. The fairy inkcap, Coprinellus disseminatus, produces enormous swarms of tiny pale grey pleated caps scattered across and around rotten stumps, each one on its own separate stalk, and its caps are furrowed like a folded fan. Coprinellus micaceus forms dense clumps on wood with tawny, mica-flecked caps whose gills eventually dissolve. Small ringed species such as Kuehneromyces or Pholiota are separated at once by a ring on the stalk and a rusty brown spore print. Any small brown mushroom with a pink or rusty print is out of the running immediately.

A Working Sequence

Dense bundle of many hair-thin brittle stalks fused at one point, small conical hygrophanous date-brown caps that fade to buff, crowded gills darkening to purplish black-brown with pale edges, no ring, no dissolving into ink, dark purple-brown spore print, damp disturbed soil over buried wood. Check the base first, the print second, and the rest falls into place.