Oak Curtain Crust

Oak Curtain Crust is the most conspicuous Hymenochaete in temperate woodland. It grows as an effused-reflexed fungus: largely flat on the wood, but with the edge turning outward into rows of thin, wavy brackets that overlap in tiers along a stump like folds of a hanging curtain. Colours are deep rust-brown to almost black, often with a brighter ochre band at the growing margin.

The genus is defined by brown, thick-walled, pointed setae embedded in the fertile layer. In the field these are invisible individually but give the underside a fine matte, velvety quality quite different from the glossy or waxy sheen of many crusts.

Colonies are perennial and can persist for years on the same stump, adding new increments in damp seasons. Old material becomes stiff, dark and curled, and can be found in every month of the year.

Fruiting body

Effused-reflexed: flat on the wood with the margin lifting into brackets typically 1–4 cm wide and barely a millimetre thick, fused laterally into long undulating tiers.

Upper surface

Dark rust-brown, chocolate or nearly black, with concentric zoning and a faintly velvety texture when young, becoming rough and often algae-greened with age. The extreme edge is paler ochre-brown when actively growing.

Fertile surface

Smooth to slightly uneven, with no pores or teeth. Matte rusty-brown to cinnamon, with a fine velvety appearance under a lens.

Flesh and spore print

Flesh is extremely thin, hard, brittle and dark brown throughout; it snaps rather than tears and does not change colour when cut. The spore print is white.

Grows on dead oak (Quercus) above all — stumps, fallen trunks, large exposed roots and cut surfaces — and also on sweet chestnut and occasionally other hardwoods. It favours substantial pieces of wood that have lost their bark, in both closed woodland and open parkland.

Because the fruiting bodies are perennial and tough, they can be recorded in any month; fresh growth with the bright ochre margin appears mainly in autumn. The species is widespread throughout Europe and the north temperate zone.

Hymenochaete rubiginosa is a saprotroph causing a white rot in oak heartwood and sapwood, breaking down lignin and leaving the residual timber pale and fibrous. It is a long-term occupant of large woody debris, sometimes covering a whole stump.

Growth is incremental: existing tiers thicken and new marginal bands are added when conditions are damp, so a single colony can persist for many years. Spores are shed from the smooth undersurface of the reflexed edges and colonise newly exposed oak wood elsewhere in the wood.

Stereum hirsutum forms similar tiered thin brackets but is bright yellow-orange with a hairy upper surface and a smooth pale ochre underside, never rust-brown throughout. Stereum gausapatum is browner but its fertile surface reddens when scratched, which Hymenochaete never does.

Trametes and other bracket fungi of oak stumps have a genuinely poroid undersurface, easily seen with a lens. Hymenochaete corrugata is the same rusty family but remains entirely flat on hazel branches without forming brackets, and produces cement-like pads between touching branches.