Peeling Oysterling

The Peeling Oysterling is the largest and most frequently encountered member of Crepidotus, a genus of small stalkless gilled fungi that grow shelf-like on dead wood. All Crepidotus species share a brown spore deposit, which immediately sets them apart from the white-spored oyster mushrooms they superficially resemble.

This species is distinguished by an unusual cap structure. Beneath the surface lies a gelatinised layer, so the skin of the cap can be lifted at the margin and stretched out like a thin sheet of rubber before it tears. No other common wood-dwelling fan-shaped fungus behaves this way, and the test can be carried out in the field in seconds.

The genus sits within the Crepidotaceae, among a group of fungi that have abandoned a central stem entirely, attaching directly by the cap edge or by a tiny lateral point. Their compact, low-cost fruit bodies allow them to exploit small pieces of dead wood that larger fungi cannot occupy.

Cap

The fruit body is 2-7 cm across, shell-, fan- or kidney-shaped, attached laterally to the wood with no true stem. The surface is whitish, buff, cream or pale tan, smooth to slightly downy, and finely hairy or scurfy at the attachment point. It is markedly hygrophanous, appearing watery brown and semi-translucent when wet and drying to pale buff. The margin is thin, often wavy or lobed, and translucently striate when moist.

Gills

Gills radiate outwards from the point of attachment like the ribs of a fan. They are crowded, fairly narrow, whitish to pale cream at first, then darkening steadily through clay to a warm cinnamon or snuff-brown as spores ripen.

Stipe

Essentially absent. The cap is sessile, joined directly to the wood, occasionally with a rudimentary stub of tissue and a whitish downy patch of mycelium at the attachment.

Flesh and spore print

Flesh is thin, soft, watery and flabby, whitish, with no colour change when cut. The diagnostic feature lies in the cap cuticle: a gelatinous layer allows the skin to be peeled from the margin and stretched elastically. The spore print is snuff-brown.

The Peeling Oysterling grows on dead deciduous wood, typically fallen branches, logs, stumps and standing dead trunks. Beech, ash, elm, willow, poplar, sycamore and alder are all frequent hosts, and it will also take to fence rails and worked timber lying in damp shade. It is rare on conifers.

Fruit bodies usually appear in overlapping tiers or scattered rows along the underside and flanks of a log, often after prolonged wet weather. The species is widespread through Europe, North America and much of the temperate world, fruiting mainly from summer into late autumn but persisting in mild damp winters.

This is a saprotrophic white-rot fungus. Its mycelium permeates the sapwood of fallen hardwood, degrading lignin along with cellulose and leaving the residual wood pale, soft and fibrous. In doing so it is part of the mid-stage decay community, arriving after bark-inhabiting pioneers have loosened the outer layers.

Because its fruit bodies are small and produced repeatedly in flushes, the fungus can keep releasing spores through much of the year from a single colonised branch. The soft, quickly rotting fruit bodies themselves become food and shelter for fungus gnats, beetles and mites, feeding invertebrate life within the deadwood habitat.

Crepidotus variabilis is much smaller, pure white and felty, grows on twigs and dead herbaceous stems rather than logs, and has a pale pinkish-brown rather than snuff-brown spore print; crucially, its cap skin is not gelatinous and cannot be stretched. Crepidotus applanatus is whiter, more fan-shaped with a distinctly grooved and pleated margin, and again lacks the elastic cuticle.

True oyster mushrooms (Pleurotus species) may look similar in outline but are far fleshier, usually have a short lateral stem, and give a white to pale lilac spore print rather than brown. Panellus species have tougher, more rubbery flesh and white spores. Schizophyllum commune is easy to separate by its densely hairy grey-white upper surface and its false gills, which are split lengthwise down the middle and roll back in dry weather.