Dyer's Polypore Identification Guide

The First Impression and the Setting

You will be in conifer woodland: a Douglas-fir plantation, a Scots pine stand, spruce or larch, or a park with mature ornamental conifers. The season is late summer into autumn. What catches the eye is a mass of shaggy plates in rust and sulphur tones, either clasped around the base of a trunk or, just as often, sitting out on apparently bare ground several metres from any trunk. That second habit puzzles people until they dig: the fruitbody is rising from a buried root.

The scale is generous. A single cap runs 10 to 25 cm across, and a fused cluster or rosette can reach 40 cm or more. Fresh growth is unmistakable in colour: a bright sulphur to deep ochre-yellow band at the actively expanding rim, with rust-orange, tawny and brown concentric zones behind it. As the season wears on the whole thing darkens through rust to a deep umber and finally to something close to black.

Reading the Upper Surface

Run a hand over the top. It is velvety, densely matted with fine hairs, sometimes coarsely tufted, and never smooth, varnished or scaly. This felty texture is the first thing that separates it from the other large brackets on conifers.

The surface is concentrically zoned, with bands of colour and often bands of differing hairiness, so that a mature cap reads like a series of rough contour lines. The margin is thick, blunt and rounded rather than thin and sharp, and in humid weather the growing edge often carries beads of clear to yellowish liquid. That vivid yellow margin against darker zones is the most memorable feature of a fresh specimen.

Shape varies with where it grows. Trunk-based fruitbodies form broad irregular fans or tiers of overlapping shelves. Ground fruitbodies, growing over a root, build a rosette of several fused caps radiating from a common central column. Old fruitbodies persist through winter as blackened, brittle, hollow shells, and can still be named by the zoned hairy top.

The Pore Surface

Turn the fruitbody over, or crouch and look underneath. There are pores here, not gills or teeth. In fresh material the pore layer is a striking greenish-yellow, sulphur or olive-yellow, and that green cast is a genuinely useful character - very few brackets show it.

The pores themselves are large enough to see without a lens: roughly one to three per millimetre, angular, irregular, frequently elongated, torn or maze-like, especially near the point of attachment. On ground-growing rosettes the pore layer runs a long way down the stem-like base rather than stopping cleanly.

Now test it. Press the pore surface firmly with a fingernail or a stick. A fresh specimen bruises promptly and strongly to dark reddish-brown or almost black, and the mark stays. That instant dark bruise on a greenish-yellow ground is close to diagnostic in this habitat. The tube layer beneath is shallow, generally under 5 mm deep, and the same rusty tone as the flesh.

Stem and Attachment

There is no true stipe of the kind a gilled mushroom has. Fruitbodies on a trunk or stump are broadly attached, sitting flush against the wood. Fruitbodies on soil have a stout, tapering, often blackening stem-like base 2 to 8 cm long which is usually partly buried.

It is worth excavating that base with a knife or trowel. Following it down to where it meets a woody root, rather than simply ending in litter, confirms the root-associated habit and rules out a genuine litter-dweller. It also tells you which tree is involved, which is part of the identification.

Flesh and Colour Change

Slice the fruitbody vertically. Fresh flesh is soft, damp, fibrous and spongy, so yielding that a thumbnail sinks into it, and it is rusty yellow-brown to a warm rust-brown throughout. Older specimens are often two-layered, with a soft hairy upper zone over a firmer, denser lower zone. Squeeze a fresh piece and water runs out.

The cut surface slowly darkens, and handling leaves brown smears on the fingers. With age and drying the whole fruitbody loses its water, becoming light, brittle and corky, and shrinks noticeably. If you carry a bottle of potassium hydroxide, a drop on the flesh turns it instantly black or dark purple-black, a quick confirmation of this group.

Taking a Spore Print

This is fiddly but possible. Cut a section carrying an intact patch of pore surface, prop it pores-down over white paper inside a closed box, and leave it overnight - the fruitbody is bulky and wet, so it needs longer than a gilled mushroom.

The deposit is white to very pale yellowish and is often thin. Under the microscope the spores are smooth, ellipsoid, colourless and non-amyloid. A pale deposit from a rust-brown fruitbody surprises people, but it is normal for this group and does not on its own separate it from its brown-fruited relatives, so treat the print as supporting evidence rather than the decisive test.

Substrate, Host and Season

This is an annual fungus, appearing from midsummer through November and then persisting as a blackened husk. It is overwhelmingly a conifer species: Douglas-fir above all, then pines, spruce, larch and cedar, with only occasional records from broadleaved trees.

Ecologically it is a butt and root rot organism, working in the heartwood at the base of living trees and continuing in stumps. Infected wood breaks down into a brown crumbly mass that cracks into rough cubes, with thin white sheets of mycelium in the cracks - if you find a conifer stump rotting that way, look around it for fruitbodies in late summer.

The practical ecological clue is simple: a large soft velvety rosette on the ground within a few metres of a conifer, or clasped to a conifer stump, is the right starting point.

Separating It From the Look-alikes

Onnia tomentosa, sometimes called Inonotus tomentosus. The closest match, since it also fruits from conifer roots and also has a felty cap. It is smaller, generally 3 to 10 cm, much thinner in section, ochre to yellow-brown without a sulphur-yellow growing edge, and its pore surface is greyish-white to pale brown, never olive-green. Its stalk is slimmer and better defined.

Laetiporus sulphureus. Bright orange above and sulphur-yellow below, which invites the error from a distance. Close up, its upper surface is smooth to suede-like rather than shaggy and zoned, its flesh is soft and pale rather than rust-brown, its pore surface does not bruise dark, and it fruits from broadleaved trunks, typically well above ground level.

Inonotus dryadeus. Cushion-shaped brackets at the base of oak, pale buff and felty when young and famous for weeping amber droplets. Its pore surface is whitish then brown, without the green tone, and the host tree is wrong.

Bondarzewia species. Large rosettes at conifer or hardwood bases, but the caps are pale tan to buff, the flesh is firm and white and does not change, and the pores are notably large and run down a well-formed white stalk.

Meripilus giganteus. Big fan clusters at broadleaved bases, especially beech, with cream pores that blacken where touched. The caps are radially fibrillose and brown-buff rather than shaggy and zoned, and there is no yellow or green anywhere.

Weathered material. Old blackened fruitbodies can be taken for burnt bracket remains. Break one open: the rusty-brown, layered, corky interior and the remains of the zoned hairy top identify it even months later.

A Note on the Name

The common name records the long history of this fungus as a source of dye for wool, which shifts through yellows, golds and greens depending on the mordant used. It is a reminder that the strong colours you are reading in the field are pigments held throughout the flesh, not just a surface effect.