Flat Crep Identification Guide

The Setting and the First Impression

Crepidotus applanatus is a fungus of damp, shaded, well-rotted hardwood, and it usually announces itself as a crowd rather than as an individual. The typical find is a fallen log or a soft stump carrying dozens of small white to cream fans, shingled in overlapping tiers down the side of the wood or clustered around a crack. Fresh material looks moist and slightly translucent; a day of dry wind turns the same colony buff and papery. The overall impression is delicate: thin, soft, watery caps that tear easily and collapse when squeezed. Because there is essentially no stem, the fans sit flat against the wood, and the whole colony can be run over with a thumb like the pages of a book.

Reading the Cap

Each cap is 1 to 5 cm across, fan-shaped, shell-shaped or kidney-shaped, sometimes almost circular where it grows from the underside of a log. The margin is thin, even, and often slightly wavy or lobed. The surface is smooth and bald over most of its extent, with a small tuft of fine white hairs at the point of attachment that is easily seen with a lens. Colour is white to cream when fresh and moist, drying to pale buff or tan from the margin inward, so a colony often shows a two-tone appearance with pale dry rims and darker moist centres. The cap is hygrophanous, meaning it changes tone markedly with water content, and when fully wet the margin becomes faintly translucent-striate as the gill lines show through the cap skin.

The Gills and Their Colour Change

Turn a fan over, or lift the whole cluster off in a slab of wood. The gills radiate outward from the point of attachment at one side, like the ribs of a fan, and they are crowded, narrow and close-packed with numerous short gills between the long ones. Their colour is the character to track: white in a young cap, then gradually shifting through pale buff to a warm pale brown or cinnamon as the spores ripen. That browning is what separates this species from the whole set of small white pleurotoid fungi that never brown at all, and it is visible without a lens if you compare a young and an old cap side by side. There is no ring, no partial veil and no cobwebby tissue between gills and wood.

Stipe, Attachment and Flesh

There is no true stem. The cap attaches directly and laterally to the wood, either broadly along one edge or through a narrow contracted point that can look like a very short lateral stub a millimetre or two long. Look closely at that attachment: it carries the white downy tuft mentioned above and is the only part of the cap that is not smooth. Slice a cap in half from margin to attachment. The flesh is very thin, soft, white and noticeably watery, and it does not become tough or leathery even in older specimens. There is no colour change on cutting, no bruising reaction and no latex. The smell is faint, damp and slightly mushroomy at most.

Taking a Spore Print

The print is the single most valuable observation for this genus and it is worth planning for. Lay one or two fresh caps gill-side down on white paper, cover them with a container to keep humidity high, and leave three to eight hours. Because these are small and thin, a good approach is to print several caps together in a group so the deposit is dense enough to read. The result is a pale brown deposit, variously described as clay-brown, cinnamon or yellowish-brown, and it is unmistakably not white. If the print is white, the specimen belongs elsewhere entirely, regardless of how similar the fans look.

Substrate, Season and Ecology

This is a wood decomposer of broadleaved logs, stumps, fallen branches and heavy debris that has already lost its bark and softened. Beech, maple, birch, poplar and oak are all common hosts, and occasional collections come from conifer wood. It favours humid, sheltered, shaded conditions such as gully bottoms, north-facing slopes and dense woodland interiors, and after a wet spell a single well-rotted log can produce hundreds of fruit bodies at once. Fruiting runs from summer through autumn, with the largest flushes following prolonged rain. The species arrives relatively late in the decay sequence, colonising wood that is already soft, and its fruiting is brief; caps collapse within days of drying.

Separating It from Look-Alikes

Within the genus, Crepidotus mollis is the main comparison: it is generally larger and browner, and its cap skin is elastic and gelatinous, so a strip pulled from the margin stretches noticeably before tearing. The cap of Crepidotus applanatus does not stretch. Crepidotus variabilis and Crepidotus cesatii are smaller, occur mostly on twigs and small woody debris, have less crowded gills and often a slightly downy cap surface. Crepidotus crocophyllus is immediately different in colour, with an orange-brown scurfy cap and yellow to orange gills.

Outside the genus, the spore print does all the work. The small white pleurotoid fungi that share the shelf habit on wood all print white: the oyster relatives, Hohenbuehelia species with their gelatinous cap layers, and Panellus species. Their gills stay white or cream and never take on the warm cinnamon tone. Schizophyllum commune is tougher and hairy above with gill edges that are split and rolled back along their length. Phyllotopsis nidulans is orange throughout and densely hairy. Resupinatus species are small, grey to blackish and cup-like. Where a decision is difficult in the field, take three caps of different ages and print them; the browning gills and the pale brown deposit will settle it.

A Field Sequence That Works

Confirm well-rotted broadleaved wood in damp shade; note tiered, stemless, white to cream fans with a smooth cap and a downy attachment point; check for crowded radiating gills; compare young and old caps and confirm the gills brown with age; test the cap margin for elasticity and confirm it is not gelatinous; then set a group print and confirm a pale cinnamon-brown deposit.