Crepidotus crocophyllus Identification Guide

The setting and first impression

Crepidotus crocophyllus is a small fungus you find by getting low. The setting is damp broadleaf woodland in warm weather: a fallen oak or maple limb going soft under the leaf litter, a mossy log beside a creek, a stack of cut hardwood at the edge of a track, or a barkless trunk lying in shade. You crouch, look along the underside and sides of the wood, and see a row of small fans, one to five centimetres across, projecting straight out of the log with no stalk beneath them, overlapping like roof slates.

From above they are unremarkable: pale fans with a scruffy brown-flecked surface. Then you tip your head or lift the branch and the identification becomes obvious, because the gills are a striking saffron to orange-yellow. Bright yellow-orange gills under a small scaly stalkless fan on hardwood is a combination almost nothing else in the genus offers, and it is the character to look for first.

Reading the cap

Take one specimen and turn it in the light.

Shape and attachment. Fan-shaped, kidney-shaped or shell-shaped, sessile, attached to the wood laterally along one edge or sometimes by a narrow point. Some specimens have a rudimentary lateral stub, but there is never a true central stipe. The margin is inrolled when young and straightens or becomes wavy with age.

Size. One to five centimetres wide, occasionally slightly more, and only a few millimetres thick.

Surface. Dry, never viscid, and this is important. The ground colour is whitish to pale yellow or buff, and over it lies a covering of fine to coarse fibrillose scales in brown, reddish brown, ochre or tawny tones, densest toward the point of attachment and thinning toward the margin. On some collections the scales are so dense the cap looks brown; on others they are sparse and the pale base colour dominates.

Margin. Often faintly translucent-striate when moist, and fringed with fine pale fibrils when young.

The gills

This is the anchoring character, so record it carefully and record it from a young specimen.

The gills radiate outward and fan-wise from the attachment point rather than from a central hub. They are close to crowded, moderately broad, and in fresh young material they are a saturated saffron-yellow, orange-yellow or apricot colour that is genuinely eye-catching for such a small fungus. As spores mature, they dull toward orange-brown, cinnamon and finally a dingy brown, so an old collection can look drab and can be missed entirely. Where a fresh flush and an old flush sit together on the same log, use the youngest specimen to judge colour.

The gill edges are typically even or slightly fringed, and there is no ring, veil zone or partial veil anywhere on the fruit body.

Base, flesh and colour change

At the point of attachment there is usually a small patch of white to pale tomentum binding the fungus to the bark or wood; check for it with a lens, as it is a useful genus character.

The flesh is very thin, no more than two or three millimetres, soft, and whitish to pale yellowish. Cut a fan in half across its width and look: it is soft and pliable rather than gelatinous, and it should not have a distinct rubbery or elastic gelatinous layer under the cap surface. There is no colour change on cutting, no latex, no blueing and no reddening. This absence matters, because one of the important look-alikes does have a gelatinous layer.

Taking and reading a spore print

Printing a stalkless fan needs a slight adjustment of technique. Cut the fungus off the wood with a sliver of bark still attached so you have something to hold, then set it gill-surface downward on white paper. Because the fan is lopsided and the gills fan outward, prop the thick attachment edge on a matchstick so the gill surface sits roughly level. Cover with a glass or bowl and leave for several hours or overnight.

The print is brown: a dull cinnamon-brown to yellowish brown, clearly warm and clearly not white. Judge it on white paper in daylight. A white print immediately excludes Crepidotus and moves the collection to genera such as Pleurotus, Panellus or Sarcomyxa.

Under a microscope, the spores are globose to broadly ellipsoid and finely warted or punctate, which is a useful confirmation because several similar-looking Crepidotus species have smooth ellipsoid spores instead.

Substrate, season and ecology

Crepidotus crocophyllus is a saprotroph on dead broadleaf wood: fallen limbs, logs, stumps, bark and woody debris of oak, maple, beech, birch, poplar and many other hardwoods, with occasional records on conifer wood. It works on wood in the middle stages of decay, often after the bark has begun to loosen, and it can fruit from the cut ends and undersides of logs as readily as from the top.

It is gregarious, commonly producing overlapping tiers of dozens of fans along a single branch. Fruiting runs from late spring through autumn, peaking in warm humid weather after rain, and it is widespread in eastern North America and reported broadly elsewhere in temperate and warm-temperate regions.

One neat structural detail worth noticing in the field: because the fungus grows sideways out of the wood, the gills are oriented so that spores can still drop clear. On a specimen growing from the underside of a log, the fan often twists or the cap curls so that the gill surface hangs downward, which is why fans on different faces of the same log look differently shaped.

Separating it from look-alikes on morphology

Crepidotus mollis. The commonest confusion. It is also a stalkless brown-tinged fan on hardwood, but its cap surface is smooth to finely scurfy with a distinctly gelatinous, elastic layer beneath the cuticle, so the cap stretches noticeably when you pull the margin. Its gills are whitish to pale brownish and never saffron-yellow, and its spores are smooth ellipsoids.

Crepidotus calolepis. Scaly like crocophyllus and often treated as close to mollis, but with whitish to pale brown gills rather than bright yellow-orange ones, and generally with a gelatinous cap layer.

Crepidotus applanatus. White to pale cream throughout, smooth rather than scaly, with a translucent-striate margin and gills that pass from white to pale cinnamon without any yellow-orange phase.

Crepidotus cinnabarinus. Fan-shaped and small, but conspicuously red to cinnabar-red on the cap with whitish to pinkish gills, an entirely different colour scheme.

Phyllotopsis nidulans. Larger, thicker, and uniformly bright orange on both cap and gills, with a densely woolly-hairy upper surface, a strong distinctive odour, and a pinkish spore print rather than brown.

Tapinella panuoides. Also stalkless on wood, with yellowish to ochre gills, but the gills are crowded, forked, wrinkled and often crossveined near the attachment, they separate easily from the cap flesh, and the substrate is typically conifer wood or worked softwood.

Sarcomyxa serotina. A late-season fan with an olive to greenish, viscid cap and orange-yellow gills, but the cap is gelatinous and slimy and the spore print is white.

Pleurotus and Panellus species. Distinguished immediately by a white spore print, and usually by larger size and thicker white flesh.

Field checklist

Small stalkless fan on dead hardwood; dry cap with brown to reddish fibrillose scales over a pale ground; bright saffron to orange-yellow gills when young; thin soft non-gelatinous flesh; white tomentum at the attachment; dull brown spore print; gregarious overlapping tiers; late spring to autumn.