Willow Bracket Identification Guide

First impressions and the setting

You usually find Willow Bracket without meaning to. Walking a wet woodland margin, a riverbank, a fen carr or a damp hedge line, you notice a hard, dark, hoof-shaped lump clamped to the trunk of a living or recently dead willow, often at head height or above. It does not look like a mushroom at all. It looks like a piece of scorched wood or a fossil that has been bolted to the tree, blackish-grey on top, cracked into a mosaic, with a paler rusty-brown band along the lower margin.

That first impression - hard, hoof-shaped, black and cracked above, perennial, on willow - is most of the identification. The rest of the work is confirming it with a knife and a lens.

Reading the bracket from above

Start with the shape. Mature fruit bodies are ungulate, meaning genuinely hoof-like: thick at the attachment, curving out and down, often as deep from front to back as they are wide. Sizes of five to twenty centimetres across are normal, and old specimens on a big willow can be larger and lumpish. Young fruit bodies are more cushion-shaped and less obviously hoofed, so shape alone can mislead on small material.

The upper surface is the giveaway. It is hard, dull and rough, grey-black to almost coal-black in the older central region, and it develops concentric ridges or steps that mark successive seasons of growth. Between and across those ridges the crust cracks into an irregular tessellated pattern, like dried mud. Moss and algae often colonise the older parts, greening the top. The extreme margin is a different colour: a narrow band of pale ochre, rust or cinnamon brown, sometimes faintly velvety, marking the actively growing edge in the current season.

The pore surface

Turn to the underside, which faces the ground and is usually flat to slightly convex. The pore surface is rusty brown, cinnamon or greyish-brown, dulling with age and often paler on the growing margin. Rub a fingertip across it and it may darken slightly, but nothing dramatic happens.

Use a lens. The pores are minute and circular, typically four to six per millimetre, so at arm's length the surface simply looks smooth and matte. Being able to count individual pores easily with the naked eye argues against this species.

Because the fungus is perennial, the tube layer is stratified. Cut vertically through the bracket with a strong knife or a small saw and you will see the tubes arranged in distinct annual layers stacked one below another, each a few millimetres deep, sometimes with a thin band of sterile brown context separating consecutive years. The number of layers gives a rough age for the bracket.

Flesh, cut surface and colour change

The context above the tubes is the single most useful confirming character. It is woody-hard, distinctly zoned or faintly fibrous, and rusty brown to dark cinnamon - never white, never cream, never pale corky. It is hard enough that a pocket knife struggles; you will often want a saw for a clean section. There is no soft, cheesy or watery layer anywhere.

Cut flesh does not change colour in the way soft fungi do. If you have potassium hydroxide solution in your kit, a drop on the context turns it black or very dark, a standard reaction for brown-flesh bracket fungi and a quick way to confirm you are in the right group rather than among the pale-fleshed brackets.

There is no stipe. Attachment is broad and sessile, and the bracket is bonded to the bark so firmly that removing one usually takes bark with it.

Spore print and microscopic backup

A spore print is awkward from a bracket still on a tree, but it can be done. Cut a section with an intact pore surface, lay it pores-down on paper, cover it with a box or bowl, and leave it somewhere humid for a day. Fresh, actively releasing material gives a white to pale cream deposit, which surprises people who expect brown spores from a brown fungus. Older or dormant brackets may deposit nothing at all, so a blank result is not evidence against the identification.

If you have a microscope, look in the hymenium for setae: dark brown, thick-walled, sharply pointed sterile cells projecting between the basidia. Their presence supports the genus. The spores themselves are subglobose, smooth and hyaline.

Substrate and season

Willow Bracket is a wood-decay fungus that attacks the heartwood of living trees, entering through wounds, broken branches and pruning cuts and producing a white rot that hollows the trunk over many years. Willow is the classic host and gives the fungus its name, but it also occurs on birch, alder and poplar, and the fungus complex around it extends to other broadleaved hosts.

Because the bracket is perennial, it is present all year round. There is no fruiting season in the usual sense; instead the margin resumes growth in spring and summer and spores are released across the warmer months. Winter is in fact a good time to look, because bare branches expose the brackets and there is no foliage to hide them. Individual fruit bodies can persist for many years on the same trunk, so a large hoofed bracket often marks a tree that has carried the infection for a decade or more.

Separating it from the look-alikes

Fomes fomentarius is the most common confusion. It is also hoof-shaped and perennial, but the upper surface is smooth to finely zoned rather than deeply cracked, and it is grey to pale grey-brown rather than black. Its context is soft, fibrous and pale tan to cinnamon, notably softer than the flint-hard rusty context here, and it favours birch and beech.

Ganoderma applanatum forms flatter, shelf-like brackets with a knobbly brown crust and, decisively, a whitish pore surface that bruises instantly brown when scratched. It also dusts everything below it with cocoa-brown spore powder.

Phellinus tremulae is very similar in structure but is essentially confined to aspen and tends to form a more triangular bracket, often high on the trunk.

Phellinus pomaceus occupies the same structural niche on blackthorn, plum and other Prunus species, and is usually smaller and more cushion-shaped.

Inonotus species share the brown context but are annual, softer, more fibrous and often develop a yellowish or golden tone, and they collapse and rot away rather than persisting as hard hoofs.

Fomitiporia robusta on oak is another hard, black-crusted relative; host tree and a more massive, less regularly hoofed outline separate it in most cases.

Quick field checklist

Hoof-shaped, rock-hard, perennial with stratified tube layers, black cracked upper crust with a rusty growing margin, rusty-brown woody context, minute pores at four to six per millimetre, broadly attached to a willow or another broadleaved trunk. That set of characters is Willow Bracket.