Wrinkled Crust Identification Guide

The Moment of Finding It

This is a fungus you meet by turning something over. You are in damp broadleaf woodland in late autumn or winter, the leaves are down, most gilled fungi have gone over, and you roll a fallen birch or beech branch to see what is underneath. Spread across the bark or the exposed wood is a patch of colour that does not belong to the log: apricot orange, salmon pink, sometimes with violet or lilac-grey shading, several centimetres to a couple of hand-spans across, with a distinctly paler, almost white, fuzzy edge. Touch it and it is cool and slightly waxy, like a thin layer of set jelly rather than paint. That combination of warm colour, waxy feel and a fringed pale margin is the whole first impression.

Reading the Structure

There is no cap, stipe or gill to work through. Phlebia radiata is resupinate, which means it lies flat against its substrate with the fertile surface facing outward, like a spilled patch. Start at the centre of the patch. There you will usually find low warts, blisters or short irregular ridges, and from that centre the ridges run outward in radiating lines, sometimes branching, sometimes joining into shallow lozenge-shaped pockets. The pattern is why the name radiata sticks. In older or thicker patches the folds crowd together and merge into a coarse brain-like crumple; in thin young patches they may be little more than radiating wrinkles on an otherwise smooth film.

Work outward to the margin next, because it carries diagnostic weight. A fresh, actively growing patch finishes in a narrow zone that is paler than the rest, whitish to cream, slightly cottony or fringed, and often clearly separable from the wood with a fingernail. Where two patches meet they simply fuse into a single sheet with a wavy internal boundary.

Colour and Texture, Wet and Dry

The colour range genuinely varies and you need to allow for it. Bright material is orange to orange-red; other patches sit closer to flesh pink, purplish pink or greyish violet, and one log can carry both. Moisture drives much of it. Soaked material is translucent, gelatinous and glowing; the same patch after a dry week contracts, hardens to a thin horny crust, loses the translucency and dulls towards brownish orange. Rewetting brings back a good part of the colour. When you cut a section, the layer is only one to two millimetres thick and shows no distinct zones, no cottony middle and no colour change on exposure. There is no bruising reaction to look for.

Getting a Spore Print

Crusts can be printed, it just takes a little arranging. Cut a piece of the colonised branch, or peel a strip of the crust if it lifts cleanly, and suspend or prop it with the fertile face downward a few millimetres above a strip of glass laid on dark card. Enclose the whole thing under a box or upturned bowl so the humidity stays high, and give it overnight. A good print is a faint whitish bloom on the glass, best seen by tilting it against the light. Under the microscope the spores are the confirmation: very small, colourless, smooth and sausage-shaped, curved along one side, and the hyphae carry clamp connections. Small allantoid spores plus a waxy radiating crust is a tight combination.

Substrate, Season and Ecology

This species is a wood decayer, one of the white rot fungi that break down both lignin and cellulose and leave the wood pale, soft and fibrous. It works on dead broadleaf material, most often fallen birch, beech, alder, ash, hazel and oak, on both bark and exposed heartwood, and it is happiest on damp fallen branches and small logs lying in contact with the ground. It occasionally appears on standing dead wood and on cut stacked timber. Coniferous wood is unusual for it.

The season is late. Fruiting builds through autumn and continues into winter, and the crusts survive frost, so this is one of the reliable finds on a cold January walk when almost nothing else is fresh. In the same patch of woodland you will often find several logs carrying it once you get your eye in.

Separating the Look-alikes on Structure Alone

The jelly rot, Phlebia tremellosa, is the closest relative in the field and the commonest confusion. It starts resupinate, but as it matures the upper edge peels away from the wood to form a narrow reflexed shelf with a white hairy upper surface. Its fertile face is more translucent and jelly-like, cream to pinkish rather than orange-red, and the folds form a network of shallow pits rather than clean radiating lines. Look for that turned-out hairy brim.

Phlebia rufa is duller, tan to rusty ochre, and its folds anastomose into a coarse net that can look almost poroid, without the strong radial pattern or the bright colour. Phlebia livida is grey to blue-grey and much smoother, effectively a waxy film with only faint wrinkling.

Silverleaf fungus, Chondrostereum purpureum, is purple to lilac-brown, but its fertile face is essentially smooth to slightly bumpy, never radially ridged, and it develops small reflexed brackets with a woolly white upper surface along the edge of the patch. Byssomerulius corium is whitish to cream, thin, leathery and peelable, with a shallow merulioid wrinkling and none of the warm colour.

Among true jelly fungi, the orange Tremella and Dacrymyces species are not resupinate crusts at all: they sit as discrete cushions, lobes or blobs on the wood and can be lifted off whole, while Wrinkled Crust is an adherent sheet whose form follows every contour of the bark beneath it.

Field Checklist

• Flat, adherent crust on dead broadleaf wood, often on the underside of fallen branches
• Orange, salmon or violet-tinged, waxy and slightly gelatinous when moist
• Ridges radiating outward from a warty centre
• Pale whitish, fringed, cottony growing margin
• Dries to a hard thin horny film and recovers when wetted
• Spore print white; spores tiny, curved and sausage-shaped
• Late autumn through winter, frost tolerant