Peeling Oysterling Identification Guide

First Impression and Setting

You are walking a damp deciduous wood in late summer or autumn and a fallen ash or beech trunk carries a row of small, pale, shelf-like caps along its upper flank. They have no stem worth the name. Each one is a soft, floppy, shell or kidney shape attached to the bark by one narrow point, often overlapping in loose tiers, the whole colony looking limp and slightly translucent after rain. That flabby, watery, stemless look on dead broadleaf wood is the Peeling Oysterling's opening statement.

Before touching anything, note the substrate precisely, whether it is a standing dead branch, a fallen trunk, or a worked timber, and note the tree species if you can. Then note the attitude: Crepidotus caps hang with the gills facing outwards and downwards, and young ones often start as small white tufts of down on the wood.

Reading the Cap

The cap is 1-7 cm across, fan-, shell- or kidney-shaped, convex at first and flattening, with a margin that is inrolled when young and often becomes wavy or lobed. The surface is smooth or very finely downy, and around the attachment point there is usually a small patch of whitish tomentum where the fruitbody grips the bark.

Colour is strongly hygrophanous. Wet, the cap is ochre-brown, tan or dull cinnamon and looks water-soaked, sometimes with a faintly striate margin. As it dries it pales to cream, buff or dirty whitish from the margin inwards, so a single tier can show three shades at once. Do not treat colour as diagnostic on its own.

The Peeling Test

This is the species' party piece and the reason for its English name. The cap carries a distinct gelatinous, elastic layer beneath the surface. Pinch the very edge of a fresh cap between finger and thumbnail and pull gently towards the attachment point. The skin lifts away as a rubbery, stretchable film that can be drawn out well beyond its resting length before it parts, and the flesh beneath is soft and watery.

In practice this is the fastest way to separate C. mollis from the small white Crepidotus species, whose caps tear rather than stretch. Do the test on fresh, moist material; a sun-dried specimen loses much of the elasticity, and a frozen one loses all of it.

Gills, Attachment and Flesh

Turn a cap over. The gills radiate outward from the attachment point, sometimes from a rudimentary lateral stub of a stem, fanning across the underside. They are moderately crowded, of unequal length with plenty of short ones, and the edges are finely fringed under a lens.

Gill colour is a maturity clock. They begin whitish or pale cream, shift through pinkish buff and clay, and end up cinnamon to snuff-brown as the spores ripen. A mature colony often dusts the caps below it with brown powder, which is a useful hint before you even take a print.

The flesh is thin, soft, watery and pliable, whitish, and it does not change colour on cutting or bruising in any dramatic way, though handled specimens may go a slightly deeper tan. There is no latex, no blueing, no reddening. The odour is faint and indistinct.

Taking a Spore Print

The fruitbody has no stem, so lay the whole cap gill-side down on white paper, weight it very lightly with a coin, and cover it. Four to six hours gives a good deposit. The print is clay-brown to snuff-brown, a warm dull brown quite unlike the white deposits of most other stemless wood-dwelling gilled fungi. That colour is the single most decisive character in the whole genus.

Under a microscope the spores of C. mollis are smooth, brown, ellipsoid, roughly 7-10 x 5-6.5 microns, with no ornamentation and no reticulum. The smooth ellipsoid spore separates it cleanly from the globose-spiny and sausage-shaped-warty spores of its small white relatives.

Substrate, Season and Ecology

Crepidotus mollis is a wood decay fungus of dead broadleaf material: fallen trunks, stumps, thick branches and occasionally worked timber, with ash, beech, elm, sycamore, poplar and willow among the frequent hosts. It is essentially absent from conifers. It works as a saprotroph, softening dead sapwood, and it is often one of the earlier gilled fungi to colonise a large fallen limb.

The season runs from early summer to late autumn, sometimes into mild winter spells, with flushes following rain. Colonies can be prolific, dozens of caps in shingled tiers along a single log, and old fruitbodies collapse into shapeless brown flaps rather than persisting.

Separating the Look-Alikes on Morphology

Crepidotus variabilis is much smaller, rarely over 2 cm, pure white and stays white, grows on twigs and dead herbaceous stems rather than big logs, and its cap is not elastic. Microscopically its spores are cylindric to slightly curved and finely warted.

Crepidotus applanatus is white to cream with a translucent-striate margin and a flat, fan-shaped cap that lacks the stretchy gelatinous layer. Its spores are globose and finely spiny.

Crepidotus cesatii and C. luteolus are again small, pale to faintly yellowish, on twigs, with globose or ellipsoid ornamented spores and no peeling skin.

Panellus and Pleurotus species share the stemless bracket-like habit but have firm, tough or rubbery-elastic flesh, gills that stay pale, and above all white spore prints.

Hohenbuehelia species do have a gelatinising layer in the cap, so the peel test alone can mislead; the spore print settles it, being white rather than brown, and the gill edge carries thick-walled metuloid cystidia under a microscope.

Phyllotopsis nidulans is bright orange and densely hairy all over, unmistakable in the field.

Schizophyllum commune is greyish, densely felted-hairy, tough and dry, and its underside is made of split, folded false gills, not true blades.

Field Checklist

Stemless shell-shaped caps in tiers on dead broadleaf wood; soft watery flesh; hygrophanous ochre-to-cream cap with white down at the attachment; a rubbery cap skin that stretches when peeled; gills radiating from the attachment, whitish then cinnamon-brown; clay-brown spore print; smooth ellipsoid spores.