Gilled Polypore Identification Guide

The first look

A fallen birch trunk in a damp wood, or a cut stump at the edge of a ride, at almost any time of year. Along the upper side of the log is a line of overlapping brackets, each one a semicircle or fan attached broadly to the wood with no stem at all. From above they look like nothing special: pale, hairy, concentrically banded, often with a green cast where algae have colonised the older parts.

Then you crouch and look at the underside, and the identification is essentially complete. Instead of the fine pore surface you expected, there are gills. True radiating blades, running from the point of attachment out to the margin, thick and leathery and unmistakable. A bracket fungus with gills is a small enough club that this one character does most of the work.

Reading the upper surface

Brackets are 3 to 10 cm wide, occasionally larger, and 3 to 8 mm thick at the point of attachment, tapering to a thin margin. They are sessile, broadly attached, semicircular to kidney-shaped or fan-shaped, and they very often fuse laterally into long ranks or grow in overlapping tiers down a trunk. On the underside of a fallen log they can be partly spread and shelf-like at the same time.

The upper surface is finely hairy, velvety or coarsely tomentose, and it is marked with concentric zones of texture and colour. Colours are muted: whitish, cream, pale grey, buff, ochre, sometimes with darker grey-brown or faintly reddish bands towards the base in weathered material. Old brackets are commonly dulled to grey or coloured green by a film of algae, which can hide the zoning completely, so read fresh growth at the margin rather than the aged centre.

The margin itself is thin, sharp, often paler than the rest, sometimes wavy or lobed, and it is the actively growing edge.

The gills

This is the character to examine closely. The fertile surface consists of radiating lamellae, arranged like the gills of an agaric but built of tough, leathery tissue rather than soft flesh. They run from the attachment point outwards, and typically number roughly ten to twenty per centimetre measured around the margin.

Several details are worth noting under a hand lens. The gills frequently fork as they run outwards, and they anastomose, meaning neighbouring blades join and cross-connect, especially towards the point of attachment. In some collections the gills near the base break down into a maze-like or partly poroid pattern before resolving into clean blades further out. Gill edges may be entire or slightly torn and split in old material.

Colour is white to cream when fresh, ageing through pale buff to tan, ochre or dull grey-brown. Fresh actively growing brackets have paler, more clearly defined gills; a year-old bracket that has overwintered can be grey and ragged.

Flesh, texture and cutting

Cut a bracket in cross-section from margin to attachment. The flesh layer is thin, roughly 1 to 4 mm, and it is white to pale cream. Crucially it stays white: it is the same colour as the gill tissue below it, with no dark line separating the two layers.

Texture is tough, corky to leathery, and flexible when moist, becoming rigid and hard when dry, then softening again when it rehydrates. You cannot dent it with a thumb and you will not tear it neatly by hand; a knife is the way to sample it. There is no colour change at all on cutting or bruising, no latex, and no distinctive odour beyond a faint woody smell.

Because it is tough and persistent, an individual bracket lasts many months, and a log can carry several generations of brackets at once in different states of weathering.

Taking a spore print

Getting a print from a tough bracket is more fiddly than from a soft agaric but perfectly achievable, and it is worth doing at least once.

Cut a fresh, actively growing bracket free of the wood with a knife, keeping it as intact as possible. Lay it gills-down on a sheet of dark paper, on glass or on aluminium foil. Put the whole assembly inside a sealed box or under a bowl with a damp piece of paper towel alongside to keep the humidity high, and leave it for twelve to twenty-four hours somewhere cool.

The deposit is white and rather sparse. Dark backing is essential. Only fresh material that is actually sporulating will deliver, so choose brackets with clean, pale, well-formed gills and avoid grey, algae-covered veterans.

Substrate, season and ecology

This is a wood-decay fungus and it will not be found on soil. It fruits on dead hardwood: fallen trunks, standing dead stems, stumps, large branches and worked timber left outdoors. Birch is the classic host, and the species is often abundant on birch logs, but beech, oak, alder, willow, hazel, cherry, maple and other broadleaves all support it.

It causes a white rot, degrading lignin as well as cellulose, so the decayed wood becomes pale, soft, fibrous and eventually stringy or spongy. It behaves as a saprotroph, colonising wood that is already dead, and it is one of the common early to mid-stage colonisers of fallen birch.

Brackets are annual, produced mainly in summer and autumn, but because they are tough and weather-resistant they persist through winter and are findable in every month of the year. Distribution is broad across the temperate northern hemisphere.

Separating the look-alikes on morphology

Trametes versicolor and other true Trametes species share the thin, zoned, hairy bracket, but their fertile surface is a fine pore layer, not gills. A hand lens settles it immediately. T. versicolor is also usually far more vividly and variously zoned.

Gloeophyllum sepiarium is the closest structural mimic, with a genuinely gilled underside. It differs in three readable ways: its gills and flesh are rusty brown to dark brown rather than white, its upper surface carries warm orange-brown and rust tones, and it grows on conifer wood, including sawn timber and fence posts. It causes a brown rot, so the wood beneath it is dark, crumbly and cracked into cubes rather than pale and stringy.

Daedaleopsis confragosa grows on the same hosts, especially willow and birch, and its underside is elongated and maze-like, sometimes almost gill-like at the margin. Its pore surface bruises pinkish to reddish-brown when scratched, and its flesh and older brackets take on distinct reddish-brown tones.

Daedalea quercina is much thicker and heavier, up to 3 or 4 cm through, with pale wood-coloured corky flesh and a deep labyrinth of thick-walled maze-like pores, and it grows chiefly on oak.

Schizophyllum commune is small, grey-white, densely woolly above, and its false gills are split lengthways down the middle and roll back when dry, which is visible under a lens.

Trichaptum species are thin brackets with lilac to purple tints on the margin and an underside that starts poroid and breaks down into ragged teeth.

Lentinellus and Panellus species can also present gills on wood, but they are fleshy or gelatinous rather than corky, and they usually have at least a rudimentary lateral stem.

Field checklist

Hardwood substrate, especially birch; sessile fan-shaped bracket in overlapping tiers; hairy zoned pale upper surface, often algal green; radiating leathery gills below, forking and cross-connected; white flesh continuous with white gill tissue; tough corky texture with no colour change on cutting; white spore print. That set is stable across the whole season and separates the species from everything that resembles it.