Cinnamon Bracket
Hapalopilus nidulans
Also called tender nesting polypore, purplepore bracket
A soft, evenly cinnamon-coloured bracket whose cap, flesh and pores are all the same warm ochre-brown, and which turns brilliant violet where a drop of alkali touches it.
Overview
The Cinnamon Bracket (Hapalopilus nidulans, also published as Hapalopilus rutilans) is a small, soft annual polypore that is unusually easy to name once you notice how completely uniform its colouring is. Cap, flesh and pore surface are all the same warm cinnamon to ochre-brown, with no contrasting layers when the bracket is cut in half.
The genus Hapalopilus takes its name from the soft, almost cheesy texture of the fresh fruit body, which can be dented with a fingernail and which dries to something light and brittle. Only a few species occur in the temperate Northern Hemisphere, and this is by far the commonest.
Its other claim to distinction is chemical: a drop of potassium hydroxide or household ammonia on any part of the fruit body produces an instantaneous, vivid violet to purple stain. Few field reactions in mycology are as dramatic or as unambiguous, and the colour change is the reason for one of its alternative English names.
How to identify it
Cap
Annual, soft and light, forming semicircular to fan-shaped or cushion-like brackets 3-12 cm across and 1-4 cm thick, often several fused along a branch. The upper surface is finely velvety to nearly smooth, unzoned or only faintly so, and coloured a uniform warm cinnamon, ochre or pale tan-brown. The margin is thick and blunt when young, thinning and sometimes becoming wavy with age.
Pores
The pore surface is the same cinnamon-buff as the cap, perhaps a shade paler when very young. Pores are small and angular, roughly 2-4 per millimetre, and the tube layer is not sharply separated in colour from the flesh above, so a vertical cut looks almost homogeneous.
Flesh and spore print
The flesh is soft, spongy and slightly fibrous when fresh, drying light, brittle and easily crumbled. It is the same ochre-cinnamon colour throughout. A drop of potassium hydroxide or ammonia solution turns cap, flesh and pores an intense violet-purple within seconds, which is the definitive field test. The spore print is white.
Where and when it grows
The Cinnamon Bracket fruits mostly on dead branches that are still attached to living hardwood trees, which is unusual enough to be a helpful habitat clue. Oak, birch, beech, hazel, hawthorn and various other broadleaves are all used, and it also appears on fallen branches and on standing dead wood. It is rare on conifers.
The species is widespread but seldom abundant across Europe, temperate Asia and North America. Fruiting is concentrated from late summer through autumn, and the dried brackets can persist attached to the branch well into the following year, faded to a duller brown but still giving the violet alkali reaction.
Ecological role
Hapalopilus nidulans is a white-rot saprotroph specialising in small-diameter dead hardwood, particularly the dead branches retained in the crowns of living trees. Its mycelium degrades lignin and cellulose together, leaving the branch wood pale, soft and crumbly.
By working on attached deadwood high in the canopy, it occupies a niche that many ground-dwelling decomposers never reach, and it contributes to the natural shedding of dead limbs. The soft decayed wood it leaves behind is readily excavated by wood-boring beetles and is an important resource in the deadwood cycle of mature broadleaved woodland.
Similar species
Several soft annual brackets share the general shape but not the uniform colouring. Postia and Tyromyces species are white to pale grey, and their flesh stays pale rather than cinnamon. Aurantiporus and Pycnoporellus species can be orange-toned, but Pycnoporellus fulgens is a brighter rusty orange with larger, more ragged pores and a distinctly fibrous texture, and Aurantiporus fissilis is whitish to pinkish cream.
The Dyer's Polypore (Phaeolus schweinitzii) is far larger and coarser, grows at the base of conifers rather than on hardwood branches, and has a dark brown, zoned, shaggy cap with big angular greenish-yellow pores. Fomitopsis and Daedaleopsis species on the same branches are tough and woody rather than soft, and none of these look-alikes turns violet in alkali, which makes a single drop of potassium hydroxide the decisive separator.