Spring Brittlestem Identification Guide

The First Impression

Early spring, a damp deciduous wood, and a troop of slim brown mushrooms along the edge of a muddy path or on the litter under alder and willow by a stream. The first thing you notice is that they are not all the same colour. Some caps are dark date-brown, others are pale ochre-tan, and many are two-toned with a bleached centre and a darker outer band. That is one species drying out at different rates, and it is the signature of a hygrophanous cap.

The second impression is fragility. Pick one and the stem feels like a hollow drinking straw; nudge it and it snaps. This is a Psathyrella, the brittlestem genus, and the spring fruiting season narrows things very quickly.

Reading the Cap

Caps run 2-6 cm, occasionally 8 cm. The young shape is conical to bell-shaped, expanding to broadly convex or almost flat, sometimes retaining a low umbo. The surface is smooth and bare, without scales, becoming slightly wrinkled over the centre in old specimens.

Colour when moist is date-brown, chestnut or grey-brown; as the cap loses water it pales from the centre outward to clay-buff, greyish ochre or tan. Always look for a specimen still wet from overnight rain — the moist colour is the reference point in the descriptions.

Two margin details are worth the lens. First, when moist the margin is translucent-striate: you can see the dark lines of the gills showing through the thin flesh, running in perhaps a quarter of the way to the centre. Second, very young caps often carry a scatter of fine white veil fibrils along the extreme margin. These are fleeting, and by the time most people find the mushroom they have vanished, so their absence proves nothing.

The Gills

Gills are adnate, moderately crowded, and change colour dramatically as the spores ripen. They start pale clay-grey or greyish brown, pass through umber, and finish dark purplish brown to almost black-brown. On any one troop you can find all the stages at once.

Now bring the lens in close on a gill edge held against the light. It is white and finely fringed, contrasting sharply with the dark gill face. That white fimbriate edge is caused by a palisade of sterile cells and is one of the quickest ways to place a fragile dark-gilled mushroom in Psathyrella.

Stipe, Base and Flesh

The stem is 4-9 cm long and only 3-7 mm thick, cylindric and equal, hollow from an early stage. Colour is glassy white to pale cream, sometimes with a faint brownish tinge low down. The surface is silky-fibrillose, minutely powdery at the very apex, and the base often carries fine white down or a few short white hairs binding the litter.

There is no proper ring. At most a very young specimen shows a faint fibrillose zone where the meagre veil once touched, and this disappears fast.

The mechanical character is diagnostic. Hold the stem at both ends and bend gently: it does not flex, it fractures. Cap flesh is extremely thin, watery brown, whitish in the stem, and shows no colour change on cutting. The odour is faint and non-distinctive.

Taking a Spore Print

Because the caps are thin and dry out fast, print them promptly. Set a fresh cap gills-down on white paper or a glass slide and cover it with a cup to hold humidity. Deposits are heavy and often readable within an hour or two.

The colour of the print is the single most decisive character. It is dark purple-brown to sepia-black — clearly not the rusty cinnamon of Conocybe and Galerina, not the pure white of a Mycena, and not the jet black of Coprinopsis. Judge the colour on white paper, in daylight, with the powder scraped into a heap.

Under the microscope the spores are smooth, ellipsoid, roughly 7.5-10 x 4.5-5.5 micrometres, dark reddish brown in potassium hydroxide, and each carries a distinct germ pore at the apex.

Substrate and Season

This is a litter and buried-wood saprotroph. It fruits on woodland floors rich in decaying hardwood — buried twigs, root fragments, chips, leaf litter — and especially likes disturbed edges: path sides, banks cut by machinery, riverside thickets, the ground around old stumps of ash, elm, poplar and willow.

Season is the character that gives the species its name. It is a spring fungus, running roughly March to June, and in April it is often the dominant medium-sized brown agaric in damp deciduous woodland. It appears in scattered troops and small groups rather than tight clumps, sometimes in large numbers along a single path edge.

Separating the Look-Alikes on Morphology

Psathyrella candolleana. The most frequent confusion. Its cap dries to a much paler cream or nearly white, it usually retains conspicuous tooth-like veil fragments hanging from the cap margin, the gills often pass through a lilac-grey phase, and it is typically clustered on or beside hardwood stumps and in lawns. It also fruits later, from late spring into autumn.

Psathyrella piluliformis. Grows in dense clusters directly on hardwood stumps and logs rather than scattered on the litter, has a richer date-red moist colour, a more persistent white fibrillose veil at the cap margin, and is mainly an autumn fungus.

Psathyrella multipedata. Immediately recognisable by its habit: many long slender stems arising from a single fused basal mass, forming a bouquet. Caps are smaller and paler.

Psathyrella corrugis and relatives. Very much more slender, with a long rooting stem base and, with a lens, a pinkish tinge to the gill edge.

Conocybe species. Similar fragility, but the caps are more sharply conical, the stems are finer and more cleanly striate, and the spore print is rusty cinnamon rather than purple-brown.

Panaeolus species. Gills are mottled and blotchy from uneven spore ripening rather than evenly coloured, the print is jet black, and the habitat is dung or manured grassland rather than woodland litter.

Coprinellus micaceus. Clustered at hardwood bases, with a tawny, radially grooved cap dusted with glistening granules when young, and gills that eventually collapse into an inky mess.

Quick Field Checklist

• Spring, damp deciduous woodland, path edges and buried hardwood debris
• Cap 2-6 cm, date-brown when moist, drying pale from the centre; margin translucent-striate when wet
• Gills adnate, clay-grey to dark purplish brown, with a white fringed edge under a lens
• Stem white, hollow, silky, ringless, and brittle enough to snap when bent
• Flesh very thin and watery, no colour change on cutting
• Spore print dark purple-brown; spores with a distinct germ pore