Crimped Gill

Plicaturopsis crispa is a small, leathery, shelf-forming fungus that colonises fallen hardwood branches in large numbers, often turning a single fallen birch limb into a ruffled ribbon of overlapping fans. Despite its gill-like underside it is not closely related to the ordinary agarics; it sits in the Amylocorticiaceae, a family whose members are mostly flat crusts. Plicaturopsis represents a lineage in which a crust-like ancestor has bent its fertile surface outward into folds and lifted the margin free of the wood.

What looks at first like a miniature bracket fungus with gills turns out, on close inspection, to be something in between. The fertile underside carries blunt, waxy, repeatedly forking folds that run and merge into one another, quite unlike the clean, blade-like gills of a true agaric. Between these folds the surface is smooth and slightly wrinkled, so the whole underside has the look of crumpled fabric.

The species is widespread across the cool-temperate Northern Hemisphere and is one of the more conspicuous late-season fungi of northern woodland. Fruit bodies are tough and pliable rather than fleshy, and they shrivel in dry weather then swell and revive after rain, which allows a single flush to remain recognisable for many weeks into the winter.

Fruiting body

Each fan is 1-3 cm across, sometimes reaching 4 cm, shell-, fan- or kidney-shaped, attached to the wood by a narrow point or a short lateral pad rather than a true stem. Fans grow in dense overlapping tiers and rows, frequently fusing side to side into wavy ribbons along a branch. The upper surface is finely felted or velvety, marked with faint concentric zones of ochre, tawny, cinnamon and orange-brown, and is paler toward the edge. The margin is thin, strongly wavy and crimped, and almost always cream to white, giving a bright rim that contrasts with the tan disc.

Fertile underside

The underside is cream, white or pale buff, ageing to pinkish-buff or greyish. It is covered in low, blunt, waxy folds that radiate from the attachment point and fork and anastomose repeatedly, joined by shallow cross-wrinkles. These folds are much thicker and duller-edged than true gills and cannot be separated cleanly from the flesh. In dry weather the whole underside contracts and the folds roll inward.

Flesh and spore print

The flesh is very thin, whitish, rubbery-tough and pliable when moist, becoming hard and brittle when dry, then reviving on wetting. There is no stem to examine. The spore print is white; spores are small, sausage-shaped and give an amyloid reaction with iodine, a microscopic detail that helps place the species in its family.

Plicaturopsis crispa is a wood-inhabiting fungus of dead attached and fallen hardwood, showing a marked preference for birch (Betula) and also fruiting readily on beech, alder, hazel, hornbeam and cherry. It concentrates on branches and slender trunks from finger-thickness up to about arm-thickness, and rarely appears on large logs or stumps. Dense colonies frequently develop on brash piles and on storm-fallen crowns still lying above the ground.

Fruiting runs from early autumn through the first frosts and often persists into winter, with dried fans reviving after rain. The species is distributed across northern and central Europe, temperate and boreal North America and temperate East Asia, and is most abundant in cool, moist deciduous and mixed woodland, particularly in northern birch forest.

This is a saprotrophic fungus and a white-rot decomposer: its mycelium breaks down both lignin and cellulose in the branch, leaving pale, fibrous, bleached wood. It specialises in small-diameter deadwood, a resource that dries and rewets rapidly, and its tough, reviving fruit bodies are an adaptation to exactly that unstable microhabitat.

By breaking down twigs and branch wood, Plicaturopsis crispa plays a substantial part in the early and middle stages of woodland litter turnover, returning nutrients from the canopy to the forest floor. Because its colonies remain fertile late into the year, it releases spores at a time when most fleshy fungi have finished, and the shrivelled fans continue to shelter small invertebrates through the winter.

Plicatura nivea is the closest relative and is similar in size and form, but its upper surface is whitish to pale grey rather than tawny-zoned, and it fruits mainly on alder. Stereum species such as Stereum hirsutum form comparable tan zoned fans on hardwood, but their undersides are completely smooth, without any folds. Schizophyllum commune is also small and fan-shaped, but its upper surface is coarsely white-hairy and its underside carries gill-like plates that are split lengthwise into two lips.

Small Crepidotus species can form pale brackets on the same branches; they are soft and fleshy rather than leathery, have true knife-edged gills, and drop a brown spore print instead of a white one. Panellus species have true gills too, plus a distinct short lateral stem.