Variable Webcap

Variable Webcap (Cortinarius variicolor) belongs to the enormous genus Cortinarius, the webcaps, named for the cobwebby cortina that stretches from cap margin to stem in young fruitbodies. It sits in the group traditionally called Phlegmacium — large, fleshy species with a viscid cap but a dry stem — and is one of the more substantial webcaps of northern conifer forest.

The species earns its name from the way its colours shift as it matures. Young caps often carry a distinct violet or lilac wash near the margin, and the gills begin bluish-violet, but both fade to dull clay and finally to rust as the spores ripen. An older specimen photographed alone can look like a plain brown mushroom; a group showing several ages tells the story much more clearly.

Within the fungal world it represents the classic ectomycorrhizal woodland fungus: a long-lived underground mycelium partnered with tree roots, sending up short-lived fruitbodies for a few weeks each year. Its bulk, its violet-flushed flesh and its association with calcareous conifer ground make it a useful reference point for learning the Phlegmacium webcaps.

Cap

Broad and fleshy, roughly 5–12 cm across, at first hemispherical then flattening with a broad low umbo. The surface is slightly viscid in wet weather and dries silky-fibrillose, coloured grey-brown, olive-brown or ochre-brown, typically with a violaceous or lilac cast towards the incurved margin when young. Fine innate radial fibrils are often visible against the ground colour.

Gills

Crowded, adnate to slightly notched at the stem, pale bluish-violet or lilac-grey in youth, passing through clay-buff to a deep cinnamon-rust as spores mature. The gill edges are usually slightly paler and finely uneven. In young fruitbodies the whole gill face is veiled by the pale cortina, which collapses onto the upper stem and quickly becomes rusty as spores drop onto it.

Stipe

Stout and firm, 5–12 cm tall and 1–3 cm thick, widening downwards to a club-shaped or bulbous base that is rounded rather than sharply rimmed. The surface is whitish, often flushed violet at the apex, with silky longitudinal fibrils and one or more indistinct rusty veil zones.

Flesh & spore print

The flesh is firm and white to pale buff, distinctly violaceous in the upper stem and immediately under the cap cuticle, fading with age. The smell is earthy to slightly mealy. The spore print is rusty brown; under the microscope the spores are almond-shaped and coarsely warted, as in most webcaps.

Cortinarius variicolor is a woodland species of coniferous forest, appearing most often under Norway spruce and to a lesser extent pine, usually on neutral to calcareous soils with a deep moss or needle layer. It favours mature, undisturbed stands and often fruits in loose troops or arcs along mossy banks and forest tracks.

The season runs from late summer through autumn, peaking after the first substantial rains of the cooling season. Its distribution is broadly northern-temperate and boreal: widespread across northern and central Europe, extending into montane conifer forests further south, with related populations reported from northern North America.

This is an ectomycorrhizal fungus. Its mycelium sheathes the fine root tips of spruce and pine, forming a Hartig net between root cells through which mineral nutrients — especially nitrogen and phosphorus scavenged from forest litter — are traded for tree-derived sugars. The relationship is obligate, which is why the species never appears away from its host trees.

Because the mycelial network is perennial and slow-growing, fruitbody troops tend to reappear in the same spots year after year, making them a rough indicator of long-established conifer stands. In doing so the fungus contributes to nutrient cycling, soil aggregation and the underground linkage between neighbouring trees.

Cortinarius varius, the Contrary Webcap, shares the conifer habitat and stout build but has a far warmer orange-ochre cap and vivid violet-blue young gills against a pure white stem, whereas C. variicolor is grey-brown with only a subtle violet flush. Cortinarius purpurascens is darker and duller and reacts by bruising purple where the gills or flesh are rubbed, a change absent here.

Among the larger Phlegmacium webcaps, Cortinarius glaucopus has a more sharply marginate, rimmed bulb and bluish-green gill tints, while Cortinarius caerulescens is far more strongly and evenly blue-violet across cap, gills and stem. All produce a rusty brown spore print, so separation rests on cap colour, the degree and position of violet pigment, and the shape of the stem base.