Variable Webcap Identification Guide

The Setting and the First Look

Variable Webcap is a heavyweight of northern conifer forest. The scene is a mature spruce stand, often with pine mixed in, a deep mossy floor, bilberry, and soil that is richer or more base-influenced than the surrounding acid podzol. It fruits from late summer into autumn, singly or in scattered troops, and it often pushes up through moss so that the cap arrives half-buried, capped with a skullcap of needles and soil.

The first impression is bulk. This is a stout, firm, heavy mushroom with a thick stem and a broad cap, and when you lift it out of the moss it feels dense in the hand. The colour is what gives the species its name: a young cap has a violaceous to bluish-lilac margin while the centre is already turning ochre-brown to date-brown, so a single fruit body shows two quite different colours at once.

Working Through the Cap

Cap diameter runs from 5 to 15 cm, occasionally more. The shape is hemispherical when young, then convex and finally broadly flattened with a low, uneven umbo and a margin that stays inrolled for a long time.

Test the surface with a fingertip. In damp weather it is viscid to slightly glutinous, enough that soil, needles and moss fragments stick to it and stay stuck. In dry weather the same cap goes shiny and tacky rather than slimy, so judge the character on fresh material or after rain. Under the slime the cuticle carries fine innate radiating fibrils that darken with age.

Colour is the diagnostic pattern rather than any single shade. Look for violet-blue tones surviving longest at the margin, blending inward into clay-brown, date-brown or reddish-brown at the disc. Old fruit bodies lose the violet entirely and become uniformly brown, so age your specimens and try to find a young one in the troop. The cap margin often carries pale remnants of the cortina as a fine fringe.

Gills, Cortina and Stipe

The gills are the second violet feature. In young buttons they are pale bluish-violet or lilac-grey, crowded, adnate to slightly emarginate, and quite narrow. That violet is fleeting: as spores mature the gills go clay, then cinnamon, then a definite rust brown, and by then the fruit body has lost most of its diagnostic colour. Gill edges are slightly paler and finely uneven.

Between cap margin and stipe, young fruit bodies carry a cortina, the cobwebby partial veil that defines the genus. Pull a button apart and you should see fine silky threads spanning the gap. There is no membranous ring. Once spores fall, the collapsed cortina remains only as a rusty fibrillose band or a scatter of rust-coloured fibrils on the upper stipe, and that rusty girdle is often all you see on mature material.

The stipe is 6 to 12 cm long and 1.5 to 3 cm thick, firm, solid and clearly clavate, swelling toward a rounded bulbous base. The bulb is rounded, not sharply rimmed with a flat marginate edge, and that shape distinction is worth checking carefully because several close relatives have a sharply marginate bulb. Colour is whitish with a violaceous flush at the apex, silky-fibrillose, discolouring ochre where handled.

Flesh, Odour and Colour Change

Slice a fruit body vertically from cap centre to stipe base. The flesh is thick, firm and white to pale cream in the body of the cap and lower stipe, but with a distinct violaceous or bluish wash in the stipe apex and immediately above the gills. That violet in section is one of the most reliable characters and should be looked for on every collection.

What does not happen is equally important. The cut flesh does not turn a strong deep purple as you watch. It may darken slightly or discolour brownish over hours, but there is no dramatic bruising reaction.

The odour is earthy, damp, cellar-like, often compared to raw potato or freshly turned soil. Crush a piece of stipe flesh in a warm hand and smell it immediately.

If you carry chemicals, a drop of dilute potassium hydroxide on the cap surface gives a dull brown to reddish-brown reaction; this is routine practice in the genus and helps confirm placement within the fleshy, viscid-capped Phlegmacium group.

Spore Print and Microscopy

Take a mature cap, place it gills-down on white paper under a cup, and leave it overnight. The deposit is rust-brown to tobacco-brown, thick and unmistakable, and it stains the paper. A rusty print plus a cortina plus a viscid cap plus violet tones narrows the field enormously before you look at anything else.

Under the microscope the spores are amygdaliform, that is almond-shaped with a slight apical taper, coarsely verrucose, and around 10 to 13 by 5.5 to 7 micrometres.

Substrate and Season

This is an ectomycorrhizal partner, forming sheathing root tips chiefly with Norway spruce and, less often, with pines. It favours mossy conifer forest on soils with some base richness, and it is commonest in boreal and montane regions. Season is late summer to autumn, peaking with the main conifer flush, and fruiting is often concentrated in the same patches year after year because the underlying mycelium is long-lived.

Separating the Close Relatives

Cortinarius purpurascens is the species most often confused. Its cap is darker, more olive- or umber-brown with a violet flush, and the decisive test is bruising: rub the gills or cut the flesh and the tissue turns a strong, obvious deep purple within a minute or two. Variable Webcap does not do this.

Cortinarius glaucopus is more slender, often gregarious in arcs and rings, and has a distinctly marginate bulb with a flat rim. Its cap is ochre to reddish-brown with bluish or greenish tints mostly at the margin, and its gills are bluish when young.

Cortinarius caerulescens is more uniformly blue-violet across cap, gills and stipe, has a marginate bulb, and grows with broadleaf trees on calcareous ground.

Cortinarius largus and the C. anserinus group are broadleaf-woodland fungi of beech and oak, with paler lilac tones and thinner flesh; habitat alone shifts the odds strongly.

Cortinarius traganus is dry and silky rather than viscid, uniformly pale lilac, with yellowish-ochre flesh and a heavy distinctive smell.

Outside the genus, Lepista nuda can look superficially similar in violet tones but has no cortina, a smooth non-viscid cap, and a pale pinkish-buff spore print rather than rust brown. Any collection with a white spore print is not a webcap at all.