Scaly Inkcap

The Scaly Inkcap, Coprinopsis variegata (long known as Coprinus quadrifidus), is one of the more substantial wood-inhabiting inkcaps of temperate hardwood forest. It fruits in crowded clusters from stumps, fallen trunks, and buried roots, with several to many bell-shaped caps rising from a common base and shedding their black spore load over a couple of days.

The cap surface carries the fungus's most memorable feature: irregular, felty, whitish to tan patches and scales, the torn remains of a universal veil that once wrapped the whole young fruit body. These patches wash off in heavy rain, so old, weathered specimens can look almost bald and are much harder to place.

Within Coprinopsis, this species belongs with the wood-rotting rather than dung-inhabiting members. It is characteristic of eastern North American hardwood forests, where it is a familiar summer sight on ash, elm, and maple debris, and a reliable early indicator that a fallen trunk has entered active decay.

Cap

3–8 cm across, at first ovoid or narrowly egg-shaped, then bell-shaped to broadly conical, and finally flattening and splitting at the margin. The ground colour is buff, tan, or greyish-brown, darker over the centre and paler toward the edge. Scattered across it are irregular whitish to pale tan felty veil patches, thickest at the disc, which rub or wash off with handling and rain. The cap becomes radially grooved as it expands.

Gills

Crowded and narrow, free to narrowly attached. They pass from white through pinkish grey and dull brown to black, then deliquesce into black ink from the margin inwards, dripping and staining anything beneath.

Stipe

5–12 cm long, 5–12 mm thick, whitish, hollow, and fibrous, often curved where fruit bodies are crowded in a tuft. It is smooth to slightly fibrillose above and typically bears a faint ring zone or scattered veil fibrils. The base is distinctive: it is clothed in a mat of hairy, cord-like whitish to ochre mycelial strands (rhizomorphs) that run out into the wood or soil.

Flesh and spore print

Flesh is thin, whitish, and fragile, with a somewhat unpleasant or sourish odour in age. The spore print is black.

A wood decomposer, fruiting in caespitose clusters directly on hardwood stumps and fallen logs, at the base of injured living trees, over buried roots, and from wood chips and debris beneath hardwoods. Preferred hosts include ash, elm, maple, box elder, and other broadleaf trees; it is rarely if ever found on conifers.

The main season is early summer to early autumn, following periods of warm wet weather. It is best known from eastern and central North America, where it can be locally abundant in floodplain and bottomland forest, in parks, and along wooded streets where old hardwoods are declining. Clusters often reappear on the same stump for several successive years.

Coprinopsis variegata is a saprotroph and a wood-rotter, colonising dead hardwood and the dead heartwood of injured living trees. Its rhizomorphs — the cords of bundled hyphae visible at the stipe base — let the mycelium travel across soil and leaf litter to reach new pieces of wood, a strategy that suits a fungus exploiting scattered logs and buried roots.

It is chiefly a decomposer of the softer, less durable components of hardwood, working in the earlier and middle stages of decay alongside bacteria and other fungi and helping open the timber up to later specialists. In doing so it recycles carbon and mineral nutrients from fallen trunks back into the forest floor. The rapid deliquescence of the gills concentrates spore release into a short, intense window, and the resulting ink often marks the log beneath a cluster with black streaks.

The Common Inkcap (Coprinopsis atramentaria) grows in similar clusters from buried wood but has a bald, smooth, pale ochre-grey cap with at most a few scurfy scales at the very centre, and it lacks the felty whitish patches and the hairy rhizomorph mat at the stipe base. The Glistening Inkcap (Coprinellus micaceus) is smaller, tawny-ochre, and covered when fresh in glistening mica-like granules rather than felty patches.

The Firerug Inkcap (Coprinellus domesticus) also fruits on hardwood with a granular veil, but it arises from a conspicuous orange-brown felty mycelial mat on the wood surface. The Magpie Inkcap (Coprinopsis picacea) is larger and unmistakable, with a dark blackish-brown cap broken by large pure white veil patches in a bold pied pattern, and it grows singly on chalky woodland soil rather than in tufts on stumps.