Dyer's Polypore

The Dyer's Polypore is the classic soft bracket of conifer root systems, appearing each year as a broad velvety rosette or a stack of overlapping shelves at the base of pines, spruces, larches and Douglas fir. Young fruit bodies are startlingly colourful, with a sulphur-yellow to bright orange growing margin surrounding a rust-brown centre, all arranged in concentric bands.

Phaeolus is a small genus in the Fomitopsidaceae, and this species is by far its best known member. It is separated from most other large annual brackets by its densely felted upper surface, its irregular, maze-like to angular pores that often run down onto a short stalk, and by the brown rot it produces, which is unusual among such conspicuous trunk-base fungi. The common name refers to the strong yellow, gold and brown pigments the flesh yields when simmered with wool, a property long exploited by textile workers.

Because it decays the roots and butt of standing conifers, it is one of the most ecologically significant fungi in coniferous forests and plantations across the northern hemisphere, and its distinctive blackened remains can be found around tree bases long after the fruiting season has ended.

Fruit body

The fruit body is 10 to 30 cm across, occasionally larger, and takes one of two forms. On soil above roots it is typically a circular to irregular rosette on a short thick central or off-centre stalk; on stumps and trunk bases it forms overlapping sessile shelves. Several caps often fuse into an irregular composite mass, sometimes engulfing grass stems and twigs as they expand.

Upper surface

The top is densely velvety to coarsely felted or shaggy-tomentose, and marked with strong concentric zones. The growing margin is bright sulphur-yellow to yellow-orange or rust-orange, while the older central area darkens progressively through rusty brown and reddish-brown to dark brown or almost black. In old specimens the whole surface becomes dark and matted.

Pores

The pore surface is greenish-yellow to olive-yellow or mustard when fresh, bruising and ageing dark brown wherever it is handled. Pores are angular, irregular and often maze-like or partly torn, about 1 to 3 per millimetre and frequently larger and more irregular near the stalk, where the pore layer runs conspicuously downward. Tubes are shallow, 2 to 8 mm deep.

Flesh and spore print

The flesh is yellow-brown to rusty brown, soft, watery and spongy-fibrous when fresh, and dries light, corky and brittle. It is faintly zoned and lacks any hard crust. The spore deposit is white to very pale yellow.

This polypore is a conifer specialist. It fruits at or very near the base of living conifers, on exposed roots, on stumps, and on the soil directly above buried roots, sometimes appearing a metre or more from the trunk where a major root runs. Douglas fir is a classic host, along with pines, spruces, larches, firs and hemlocks, and it is common in both natural coniferous forest and planted stands.

The season runs from mid-summer into autumn, with fresh brightly coloured fruit bodies developing in late summer and blackened, hardened remains persisting around the tree base well into winter and often the following spring. The species is widely distributed across the north temperate zone, being common throughout Europe, temperate Asia and North America, and it has been carried into the southern hemisphere with planted conifers.

Phaeolus schweinitzii causes a brown cubical rot of the roots and butt of conifers. Its enzymes break down cellulose while leaving much of the lignin behind, so the decayed wood turns reddish-brown, shrinks and cracks into rectangular blocks that crumble readily to powder. This is quite different from the pale stringy white rot of most large trunk-base brackets, and the cubical residue is often visible in stumps long after the tree is gone.

Infection typically starts at root wounds or through root contacts and progresses slowly upward into the lower trunk, sometimes extending several metres. The species is one of the most important decay organisms in coniferous forest, driving the turnover of the very large woody biomass locked in conifer root systems and lower trunks. Brown-rotted residue is chemically stable and long-lived, so it makes a lasting contribution to forest soil organic matter, while the hollows and softened wood it creates support insects and cavity-nesting birds.

Pseudoinonotus dryadeus forms similar large soft brackets at tree bases but grows on oak rather than conifers, has a lumpy warted top with amber droplets, whitish pores and rusty brown fibrous flesh, and causes a white rot. Inonotus hispidus is coarsely shaggy above, grows high on hardwood trunks, and has pale yellow pores ageing rusty brown.

Onnia tomentosa also fruits on conifer roots with a velvety zoned cap and a short stalk, but is smaller and thinner, duller greyish-brown to yellow-brown without the vivid yellow margin, and has greyish-brown rather than olive-yellow pores. Laetiporus species form tiered fans with smooth, hairless, bright orange upper surfaces and sulphur-yellow pore surfaces, and their flesh is white or pale rather than yellow-brown. The combination of a felted concentrically zoned top, an olive-yellow pore surface bruising dark brown, and a conifer base is conclusive here.