Destructive Pholiota Identification Guide

The find, and the setting

This is a fungus you usually meet on a floodplain, a riverside path, a shelterbelt, or an old plantation of poplars and cottonwoods in late autumn. You are walking past a great pale fallen trunk, often one that has been down a year or two with the bark sloughing off in plates, and something the size of a side plate is sitting on the upper surface. It is pale — cream, buff, dirty whitish — and it looks as though someone has stuck torn tufts of cotton wool all over it. Frequently there are only one to three fruitbodies on the whole log, sometimes a small cluster, and they are heavy and solid rather than delicate.

The first mental note to make is the host. This species is strongly tied to poplars in the broad sense — cottonwood, aspen, black poplar, balsam poplar — with willow as an occasional alternative. If the log is oak, beech or conifer, start doubting immediately.

Step one: the cap

Expect something large: 5 to 20 cm across, occasionally more on a rich trunk. Young caps are strongly convex and almost hemispherical with the margin rolled inward and hung with soft veil remnants; mature caps flatten out and often develop a low broad umbo or a slightly wavy edge.

The ground colour is pale — whitish, cream, straw or pale buff, sometimes warming to dull tan in the centre with age. Over that ground sit the scales, and their character matters. They are large, soft, cottony to fleecy patches, whitish and often slightly raised at the edges, and they are easily rubbed off with a thumb or washed away by heavy rain. They are not the sharp, erect, tawny spines you see on some relatives.

Check the surface texture under the scales in wet weather. It is at least slightly sticky or greasy when moist, drying dull. Feel the cap margin too: it usually carries a fringe of hanging cottony veil that shreds as the cap expands.

Step two: the spore-bearing surface

This is a gilled fungus, so turn it over. The gills are close to crowded, moderately broad, and attached to the stem — adnate to slightly notched, sometimes with a short decurrent tooth in age. They are not free from the stem, which immediately rules out several pale-capped groups.

Colour is a two-stage story and both stages are useful. Very young gills are whitish to pale cream, and if you find a button with the veil still intact they may be almost pure white. As the spores mature they shift through dull clay to a distinct cinnamon or rusty brown, and mature specimens usually show that brown dusted over the ring zone and the upper stem where spores have fallen. Look at the gill edges with a lens: they are typically slightly paler and finely uneven, sometimes minutely fringed.

Step three: the stem

The stipe is thick and solid — often 1.5 to 4 cm wide and 5 to 15 cm long — and it is frequently curved or bent, since the fruitbody has to turn upward from the side of a horizontal log. It usually tapers downward and often ends in a rooting, sometimes slightly swollen base pushed deep into soft wood.

Above, the stem is whitish and comparatively smooth. Below the ring zone it is covered in the same soft, recurved woolly scales that decorate the cap, giving it a shaggy or fleecy look. The ring itself is rarely a neat skirt: it is more often a ragged, cottony, fibrillose zone that collapses against the stem and is soon stained rusty by falling spores. On old, weathered specimens the ring zone may be reduced to little more than a line of fibres, so use it as supporting evidence rather than a requirement.

Step four: flesh and cut surfaces

Slice the fruitbody vertically from cap centre through the stem base. The flesh is thick, firm and white, and it stays essentially white; at most it dulls slowly to pale buff or brownish in the stem base after long exposure. There is no rapid blueing, reddening or blackening. In the stem base the flesh is often a little tougher and more fibrous, and long-standing specimens can be riddled with insect tunnels.

Smell is worth recording — usually faint and vaguely earthy or slightly sharp — but treat it as a secondary character, since it varies with age and weather.

Step five: the spore print

This is where the identification becomes decisive. Cut a mature cap free, lay it gills down on white paper (or half on white and half on dark card, so you can judge the tone), cover it with a bowl to slow drying, and leave it for four to twelve hours.

The deposit is brown — a warm rusty or cinnamon brown, not chocolate, not purple-black, not pink, and emphatically not white. That single result separates the species from most of the pale, scaly, log-dwelling agarics it might be confused with. Under a microscope the spores are smooth, ellipsoid, thick-walled and modestly sized at roughly 7 to 10 by 4 to 5.5 micrometres, and most show a distinct pore at the apex.

Substrate, timing and habit

The fungus is a wood decayer working on dead standing trunks, fallen logs and large stumps, and it favours wood that is already well established in decay rather than freshly fallen. Fruiting is late — typically from early autumn well into the first frosts, and it is one of the species you still find when most agarics have finished. Fruitbodies grow singly, in pairs, or in small tiers along a trunk rather than in the dense bouquet clusters some relatives form at the base of living trees.

Telling it apart on structure alone

Shaggy scalycap relatives. The commonest confusion is with the sharply scaly Pholiota of hardwood stumps. That one is dry rather than viscid, its ground colour is tawny to ochre-yellow rather than cream, its scales are erect, pointed and darker than the cap, its gills often pass through a distinctly greenish or olive-tinged phase, and it typically erupts in dense clustered tufts at the base of living trees. Our species is paler, softer-scaled, greasier when wet, and usually solitary on a fallen poplar.

Golden scalycaps. The bright golden to orange-yellow, strongly slimy caps with small flattened rusty scales, generally high up on wounds of beech and maple, are a different proposition: much more vividly coloured, thinner-fleshed, and with slender stems.

Honey fungus group. Superficially similar in stature and in having a ring, but the spore print is white, the gills stay whitish to pale flesh-coloured, the fruitbodies come in large tufts, and black bootlace strands are usually present in the wood or soil nearby.

Silky rosegill on elm. Also large, pale and log-dwelling, but its gills are free from the stem and turn pink, it has a conspicuous sac-like cup at the stem base, it has no ring, and its cap is covered in fine silky hairs rather than cottony patches.

Field-mushroom relatives. Pale, scaly caps and a ring can suggest them, but they have free gills that go pink then dark chocolate brown, a completely different spore-print colour, and they grow on soil, dung or grass rather than out of a poplar trunk.

Powdercaps and white-spored scalycaps. A few shaggy, cinnamon-scaled agarics on wood have pure white spore prints and no viscid layer; the print settles it in one step.

Field summary

Big; pale cream cap with soft cottony removable scales; slightly viscid when wet; attached crowded gills that mature rusty brown; stout, often curved, woolly-scaly stem below a ragged cottony ring zone; white unchanging flesh; rusty-brown spore print; on dead poplar or cottonwood; late autumn. That sequence, run in that order, gets you there reliably.