Common Stump Brittlestem

Common Stump Brittlestem is one of the most abundant autumn fungi of broadleaved woodland, forming crowded tufts of dozens of fruit bodies on and around old stumps. Its two-tone appearance in drying weather, dark at the rim and pale in the middle, is a signature of the genus.

Psathyrella is a large genus characterised by thin, brittle, hygrophanous caps, fragile hollow white stems that snap cleanly, and dark brown to purple-black spore deposits. Species are notoriously difficult to separate, but this one is helped by its habit, size, and substrate.

Young caps carry a fringe of pale veil fibrils along the margin, remnants of a delicate cortina-like covering, which wash away in rain. Together with the tufted growth on wood and the dark gills of mature specimens, this makes it one of the more approachable members of a demanding genus.

Cap

Usually 2-6 cm across, hemispherical then convex and finally flattened, strongly hygrophanous. Moist caps are rich date-brown to reddish tan; as they dry they turn pale ochre or buff from the centre outward, producing a distinct two-tone zoning. The margin is often hung with fine whitish veil fibrils when young.

Gills

Adnate and crowded, pale clay or greyish at first, then dark chocolate to purple-brown as the spores ripen, often with a narrow paler, minutely fringed edge visible under a lens. Mature gills may weep small droplets in damp weather.

Stipe

White to very pale buff, 3-8 cm tall and 3-6 mm thick, cylindrical, hollow, smooth to slightly silky, and conspicuously brittle so that it snaps rather than bends. There is no true ring, though a faint fibrillose zone may persist near the top.

Flesh & spore print

The flesh is thin, watery brown when moist and pale when dry. The spore print is dark purple-brown to blackish brown, best seen as a thick deposit on white paper.

It fruits in dense tufts on the stumps, fallen trunks, and buried roots of broadleaved trees, especially beech, oak, birch, and willow, and sometimes on woody debris and wood chip mulch. Fruit bodies may appear to grow from soil when the wood involved is a buried root or a stump ground out below the surface.

The main season is late summer to late autumn, often continuing until the first hard frosts. It is common and widespread throughout temperate Europe, North America, and northern Asia, and is one of the most frequently encountered fungi in managed woodland and parkland.

This is a saprotrophic wood decomposer that attacks the residual wood of dead hardwood stumps and roots, particularly wood already softened by earlier colonisers. It contributes to the later stages of stump breakdown, and repeated fruiting from the same stump can continue for several years until the substrate is exhausted.

The massive tufted fruiting habit reflects a large, well-established mycelium within a single stump. Fruit bodies mature quickly and deteriorate quickly, and because the caps are hygrophanous, the appearance of a single tuft can change dramatically between a wet morning and a dry afternoon.

Psathyrella candolleana is paler, honey-buff to almost white when dry, has a more strongly toothed veil margin, and usually grows in smaller groups from soil near stumps rather than in massive tufts on the wood itself. Hypholoma fasciculare forms similar clusters on stumps but has a bright sulphur-yellow cap and greenish-yellow gills, and a firm rather than brittle stem.

Kuehneromyces mutabilis is also tufted on hardwood stumps but has a distinct membranous ring, a scaly stem below the ring, and a cinnamon-brown rather than purple-brown spore print. Gymnopilus species on stumps are tawny orange with a rusty spore deposit and much tougher flesh.