Alder Scalycap Identification Guide

The First Impression

The Alder Scalycap (Pholiota alnicola) is usually found by looking at the wrong height. Most autumn woodland searching happens at ground level, but this species fruits in tufts from the base of standing alder trunks, from exposed roots at the waterline, and from cut stumps, often 20-60 cm above the litter. What catches the eye is a clean lemon-yellow cluster against wet grey alder bark, a colour that stands out from the browns and ochres around it.

The setting is characteristic and worth trusting. Alder carr, streamsides, fen woodland, the sodden margins of ponds, wet ditch banks: places where your boots sink. Willow and birch in similar wet ground also support it. If you are standing on dry mineral soil in a conifer plantation, reconsider.

Reading the Cap

Caps are 2-7 cm across, convex at first with a slightly inrolled margin, expanding to nearly flat, sometimes with a low broad umbo. Young caps are a striking lemon to greenish-yellow; with age the centre warms to tawny, foxy-brown or rust-ochre while the margin stays yellow, giving a two-toned effect.

The surface is smooth to slightly viscid in damp conditions and becomes shining and tacky when handled, drying to a matt or silky finish. Despite the common name, the scales are modest: fine fibrillose scales or veil fibrils scattered mainly toward the margin, often washed off entirely by rain, so a bald cap is normal in older material. Young fruit bodies usually show white cortina-like veil fibrils hanging from the cap edge.

Gills and the Spore Print

The gills are adnate, often with a slight decurrent tooth running a short way down the stipe, and they are crowded and rather narrow. Colour tracks spore maturation: pale yellow to straw in the button, then increasingly dull cinnamon to rusty-brown as spores ripen, with the gill edge frequently staying paler and finely uneven under a lens.

The spore print is the anchor for the whole genus. Take a mature cap, cut the stipe off flush, place the cap gill-down on white paper under a bowl for three to five hours, and expect a rusty ochre-brown to cigar-brown deposit. That rusty tone immediately separates Pholiota from the purple-brown of Hypholoma and the dark sepia of Agaricus, and from the pale cream of many wood-rotting agarics. Under the microscope the spores are smooth, ellipsoid and carry a small but distinct germ pore.

Stipe, Ring Zone and Base

The stipe is 4-10 cm long and 4-10 mm thick, often curved as it grows out from bark or turns to bring the cap upright, and frequently fused with its neighbours at the very base. Colour is the useful part: yellow at the apex, darkening progressively downward through rust-brown to almost blackish-brown at the base in older specimens, so a mature cluster shows a clean colour gradient along each stipe.

There is no membranous ring. Instead, look for a fibrillose ring zone in the upper third, a faint girdle of veil fibrils that often becomes conspicuous when it catches falling rusty spores. The stipe is fibrous, stuffed then hollowing, and it does not snap cleanly.

Flesh and Colour Change

Split a fruit body lengthwise. The flesh is pale yellow in the cap and upper stipe, becoming distinctly brown to rust-brown in the lower stipe. There is no dramatic bruising reaction; handling produces slow brownish staining, particularly on the stipe.

Smell the cut surface immediately. Pholiota alnicola has a strong, aromatic scent that many recorders describe as fragrant and slightly fruity, and it is markedly stronger than the faint mushroomy smell of most stump-dwelling agarics of similar size. It is not a decisive character on its own, but a strongly aromatic yellow clustered scalycap on alder is a good combination.

Substrate, Season and Ecology

This is a wood-rotting species. It colonises the butt and root region of alder, and less often willow or birch, and it can be found both on living trees showing decline and on dead stumps and fallen trunks. Fruiting runs from early autumn into late autumn, peaking after sustained rain, and clusters can be very large where a whole stump is colonised.

Because the fungus works within wood rather than litter, its position on the substrate is a genuine identification character. Trace the tuft to its point of attachment. If the base emerges from bark, from a cut surface, or from a root crown, that fits; if it emerges from soil with no wood beneath after careful digging, look elsewhere.

Separating the Look-alikes

Pholiota flammans is far more dramatically scaly, with bright chrome-yellow recurved scales over the whole cap and stipe, and it is a conifer species on spruce and pine stumps.

Pholiota squarrosa has a dry, non-viscid cap densely covered with coarse upturned brown scales, and a shaggy scaly stipe below a distinct ring zone; it clusters at the base of broadleaved trees but is stouter, browner and much rougher in texture.

Pholiota aurivella and P. adiposa are larger, with viscid caps carrying flattened gelatinous scales, and they fruit high on trunks of beech, elm and other broadleaved trees.

Pholiota gummosa is a smaller, paler species, straw to greenish-white, growing on buried hardwood debris and often looking as though it is on soil.

Kuehneromyces mutabilis forms similar tawny clusters on hardwood stumps, but its cap is strongly hygrophanous with a distinct two-tone zonation as it dries, and it has a genuine membranous ring plus a stipe covered with small recurved scales below the ring.

Gymnopilus junonius is much bigger, orange-tawny, dry and fibrillose rather than yellow and slightly viscid, with a membranous ring and a bright rusty-orange print.

Hypholoma fasciculare clusters on stumps in similar quantity and can be yellow, but its gills pass through a distinct greenish-olive phase and its spore print is dark purple-brown, not rusty.

A Working Sequence

Find the attachment point and record the host. Note the lemon-yellow young cap and tawny centre, the adnate gills, and the stipe colour gradient from yellow apex to blackish base. Check for a fibrillose ring zone rather than a membranous ring, smell the cut flesh, and take a rusty ochre print overnight. A strongly aromatic, yellow, clustered, slightly viscid scalycap on alder in wet autumn woodland is Pholiota alnicola with little room for doubt.