Tinder Conk

Fomes fomentarius is the type species of the genus Fomes, a small group of hard, perennial, hoof-shaped polypores. Its shape is so consistent that the fungus can usually be named from thirty metres away: a thick grey wedge jutting horizontally from a trunk, ridged in concentric steps like a weathered horse's hoof.

The fungus has an unusually well-defined internal architecture. Beneath the hard crust lies a soft, suede-like brown layer of tightly woven hyphae — the tissue long known as amadou, prized historically for its felt-like texture and its ability to hold a smouldering ember. Beneath that sits a stack of tube layers, one added each growing season, so a sawn specimen reads like a set of annual growth rings.

It is circumboreal, found across Europe, northern Asia and North America wherever birch grows, and is one of the most important decomposers of standing dead birch. In beech-dominated woodland it takes on the same role, and old brackets can persist on a fallen trunk long after the wood beneath has softened.

Cap

The bracket is hoof-shaped to broadly convex, 5–45 cm across and often as deep as it is wide, attached by a broad base and projecting horizontally. The crust is hard, smooth to slightly roughened, and marked by strong concentric ridges corresponding to successive seasons of growth. Colour is grey to silvery-grey, sometimes almost white on exposed specimens or tan to brown in youth, and the blunt margin is usually paler.

Pores

The pore surface is flat to slightly convex, pale grey-brown to cinnamon-buff, darkening slowly when rubbed. Pores are round and small, roughly 2–4 per millimetre. In section the tubes are stacked in distinct annual layers, often separated by thin bands of pale context, and old layers may be stuffed with white mycelium.

Stipe

None. The bracket is sessile and attached broadly to the bark, generally at a height of one to several metres on a standing trunk.

Flesh & spore print

The context is the key character: a soft, fibrous, felty layer, warm brown to cinnamon, that pulls apart like suede or kid leather and contrasts sharply with the stony crust above it. The spore deposit is white to very pale yellow — never brown — and is produced in enormous quantity in spring, sometimes visible as a haze drifting from the pore surface on still mornings.

Tinder Conk grows on the trunks of broadleaf trees, overwhelmingly birch in the north and beech further south, and also on poplar, willow, maple, alder, sycamore and occasionally other hardwoods. It colonises living but weakened trees through wounds and broken branches, then continues fruiting on the standing snag and the fallen trunk for many years.

The distribution is circumboreal and extends south through temperate Europe, across Siberia, and into North America from Alaska and Canada down through the northern states and the Appalachians. Because the bracket is perennial and extremely durable, it is present year-round; active spore release peaks in spring and continues through the warmer months.

This species causes a white rot, breaking down lignin along with cellulose so that decayed wood becomes pale, soft and finely fibrous, eventually crumbling into a fibrous mush. In birch it is often the primary agent that reduces a standing snag to a hollow shell, and its activity is a major driver of nutrient cycling in northern forests.

The hollowing it creates is ecologically valuable, opening nest cavities for woodpeckers, tits and flying squirrels. The brackets themselves support a specialised insect fauna, including several beetles that breed nowhere else, so a birch stand with abundant Tinder Conk typically carries a much richer invertebrate community than one without.

Fomitopsis betulina, the birch polypore, shares the birch substrate but forms a smooth, kidney-shaped bracket with a thin rolled margin, a soft white corky context and a white pore surface — completely different from the grey hoof and brown felty interior of the Tinder Conk. Fomitopsis pinicola is also hoof-shaped and perennial but grows mainly on conifers, has a resinous crust with a red-orange band and a white margin, and a white context rather than brown.

Phellinus igniarius is the nearest match in shape and colour: also a hard grey-black hoof on birch and willow, but its crust becomes deeply cracked and charcoal-like with age, and its context is a hard, rusty rust-brown that is woody rather than felty. Ganoderma applanatum is flatter and more shelf-like, with a white pore surface that bruises brown and a cocoa-brown rather than white spore deposit.