Violet Webcap Identification Guide

First Impression and Setting

There is no mistaking the moment you find a Violet Webcap. In damp autumn woodland, among brown litter and green moss, a mushroom appears that is so deeply purple it looks almost black in shade and glows a rich violet when a torch or a shaft of sun catches it. It is a substantial mushroom too, solid and heavy for its size, standing eight to fifteen centimetres tall with a fist-sized cap.

The setting is mature woodland on damp, often acidic, mossy ground. In Europe the classic habitats are old beech and birch woods, and damp conifer forest for the closely related northern form; in North America it is most often found in mossy conifer forest and mixed woods. It appears from late summer into late autumn, usually singly or in small scattered groups, and it favours undisturbed ground, mossy hollows and the bases of old trees.

Because it is mycorrhizal, the trees around the find are part of the record: note whether you are under broadleaves or conifers before you touch anything.

Reading the Cap

Caps are six to fifteen centimetres across, at first hemispherical with an inrolled margin, then broadly convex and finally almost flat with a low central hump.

The surface is the character to concentrate on. It is dry, never slimy, never greasy, and never shiny. Under a lens it is covered in fine, dense, upturned fibrils and small pointed scales that give it a scurfy, felted, slightly hairy look, so the cap reads as matte and almost velvety rather than smooth. Run a fingertip across it: it drags very slightly.

Colour is a uniform deep violet to blackish-purple, darkest in the centre, and it holds that colour well into maturity, dulling to a blackish or brownish-violet only in old age or after frost. Water spots and handling may leave darker marks.

The Gills

Gills are the second great character. They are deep violet to purple-black when young, moderately spaced, fairly thick and broad, and attached to the stem by a notch or narrow attachment rather than running down it.

Watch what happens with age. As the rusty spores mature, the gill faces are progressively dusted with rust-brown, so a mature specimen shows purple gill edges with a cinnamon-brown wash across the faces, and an old one can look brown overall with only a violet trace at the edge. That combination of a violet base colour overprinted by rust is unique and diagnostic in the field.

The Veil

Before you pick the mushroom, look at the gap between cap margin and stem on a young specimen. Cortinarius species carry a cortina, a veil made of fine silky threads like a cobweb rather than a solid membrane. In Violet Webcap it is violet and often sparse, stretching from the cap edge to the stem.

Once the cap expands, the cortina collapses onto the stem and forms a faint fibrillose ring zone, which soon catches falling spores and becomes a rusty-brown belt. Finding that rust-stained cobweb zone on a purple stem is often quicker than taking a print.

The Stipe, Base and Flesh

The stem is stout, eight to fifteen centimetres tall and one to two centimetres thick, widening downwards into a distinctly club-shaped or swollen base that is sometimes almost bulbous but never has a rim or a sac around it.

Surface colour matches the cap: violet, often paler and more lilac toward the top, covered in fine woolly fibrils and frequently with darker violet fibrillose belts left by the veil. Dig the base out of the moss: it is usually clothed in violet-tinged mycelial threads binding litter.

Slice the whole mushroom in half lengthways. The flesh is firm and thick, whitish to pale greyish-violet, with the strongest violet immediately under the cap skin and in the outer stem. It does not change dramatically on cutting; at most it dulls or browns slowly over several minutes. There is no latex.

Smell is a genuinely useful supporting character here. Fresh cut flesh has a distinct scent often likened to cedar wood or pencil shavings.

Taking a Spore Print

Cut the stem flush and set the cap gill-side down on white paper under a bowl for a few hours. The deposit is a strong rust-brown to cinnamon-brown, and it is the single most important character for the genus. If your purple mushroom prints white, you are not in Cortinarius at all.

Under a microscope, spores are broadly ellipsoid to almond-shaped and distinctly warted, roughly twelve to fifteen by seven to nine micrometres. The northern conifer form, often treated as Cortinarius hercynicus, has shorter, rounder spores.

Substrate and Season

Fruit bodies arise from soil and moss, not from wood, in mature woodland where the fungus is in mycorrhizal partnership with tree roots. In Europe the broadleaf form is associated with beech and birch on damp acidic soils; the conifer form grows with spruce and pine in cool, mossy forest. The season runs from late summer into the first frosts, peaking in a wet autumn.

Separating It from the Look-Alikes

Viscid Violet Cort, Cortinarius iodes, is the main confusion in eastern North America. Its cap is glutinous and slimy rather than dry and scurfy, its purple is paler and more lilac, it usually develops yellowish or whitish spots and streaks on the cap, and its gills are pale violet rather than deep purple-black.

Cortinarius hercynicus is essentially the conifer form of Violet Webcap and is separated on spore shape and habitat rather than field appearance.

Amethyst Deceiver, Laccaria amethystina, is far smaller and more slender, with thick, widely spaced, waxy-looking gills, no cobweb veil, and a white spore print.

Wood Blewit, Clitocybe nuda, shares a lilac tone but has a smooth, moist, brownish-lilac cap, crowded pale lilac gills that fade to buff, no cortina, and a pale pinkish-buff spore print.

Cortinarius purpurascens has a viscid, brownish to purplish cap and flesh that turns markedly deeper purple where cut or bruised.

Cortinarius traganus and camphoratus are paler lilac, and cutting them reveals ochre or brownish flesh inside the stem rather than violet-tinged whitish flesh.

A Field Checklist

Uniform blackish-violet colour; dry, scurfy, felted cap; thick violet gills dusted rust with age; cobweb veil leaving a rusty ring zone; club-shaped violet stem; whitish-violet flesh smelling of cedar; rust-brown spore print; from soil in mature woodland in autumn.