Destructive Pholiota

The Destructive Pholiota is the giant of the scalycaps, producing thick-fleshed fruiting bodies that can reach the size of a spread hand and a stout woolly stipe as thick as a thumb. It is a specialist of dead poplar and cottonwood, and is most often found on the cut ends of felled trunks, on stacked logs and on large fallen limbs, where it fruits singly or in small groups rather than in dense tufts.

The species has moved between genera and carries several names, most commonly Pholiota destruens, Pholiota populnea and Hemipholiota populnea. What sets it apart from most Pholiota is the texture of its veil: instead of firm pointed scales it is decorated with soft, loose, cottony white patches that peel and fall away, leaving a pale cap that can look almost bald in age.

It is a substantial wood decayer, and its epithet refers to the vigour with which it breaks down poplar timber, hollowing out logs and cut trunk sections from the inside.

Cap

The cap is large, 5–20 cm across and sometimes more, hemispherical at first and expanding to convex or broadly flat with a thick, often inrolled margin. The surface is dry and pale — whitish, cream, buff or pale tan, darkening slightly to ochre over the centre — and is decorated with large, soft, woolly white to cream veil patches that sit loosely on the surface and are easily rubbed off or washed away by rain. The margin is characteristically hung with soft cottony veil fragments in young specimens.

Gills

The gills are adnate to notched, crowded and broad, whitish or pale buff at first and darkening to clay, cinnamon and finally rusty brown as the spores mature. The gill edges usually remain paler and slightly floccose.

Stipe

The stipe is 5–15 cm long and 1–3 cm thick, very stout and firm, often curved or eccentric where it emerges from a vertical face, and frequently tapering into a short rooting or abruptly swollen base. It is whitish and shaggy with soft cottony scales below a woolly ring zone, and smoother and paler above; the ring zone is fibrillose rather than membranous and commonly turns rusty from fallen spores.

Flesh and spore print

The flesh is thick, firm and white, sometimes yellowing slightly on exposure in the stipe, with a strong, somewhat pungent or earthy odour in mature specimens. The spore print is rusty brown to cinnamon brown.

The Destructive Pholiota is strongly host-specific, fruiting on dead wood of poplars in the broad sense — black poplar, aspen, balsam poplar and cottonwood — and occasionally on willow. It favours large-diameter material: standing dead trunks, fallen logs, stumps, and above all the exposed sawn ends of recently felled trunks and stacked timber, where fruiting bodies often emerge directly from the cut face.

It has a northern temperate distribution, occurring across Europe, temperate Asia and North America wherever poplars are abundant, including riparian woodland, floodplain forest, shelterbelts and plantations. Fruiting begins in autumn and can continue into early winter, with the sturdy, thick-fleshed fruiting bodies persisting for several weeks and tolerating early frosts better than most gilled fungi.

The species is a vigorous saprotroph causing a white rot of poplar wood. Its mycelium penetrates deep into the sapwood and heartwood of large trunks, degrading lignin along with cellulose and reducing dense timber to a soft, pale, fibrous mass. Because poplar wood is comparatively soft and moist, decay proceeds quickly, and colonised logs can become hollow within a few years.

Ecologically this makes it an important agent in the turnover of floodplain and riparian woodland, where poplars are short-lived, fast-growing trees that produce large volumes of coarse woody debris. The cavities and softened wood it creates are exploited by cavity-nesting birds, bats and wood-boring invertebrates, so its decay activity contributes directly to structural diversity in these habitats.

Pholiota squarrosa is a similarly large scalycap but has a dry ochre-buff cap with firm, upturned, pointed brown scales rather than soft white cottony patches, greenish-tinged maturing gills, and forms dense clusters at the bases of living hardwoods. Pholiota aurivella has a strongly viscid golden-yellow cap with flattened gelatinous scales and fruits high on trunks, often of beech.

Cyclocybe aegerita also fruits on poplar but has a smooth two-toned cap with no woolly patches, a firm membranous ring and a tobacco-brown rather than rusty spore print. Volvariella bombycina, another large pale fungus of poplar and elm wounds, has a silky-hairy cap, free gills that turn pink, a sac-like volva at the stipe base and a pink spore print.