Green Skinhead

Green Skinhead (Cortinarius venetus) belongs to the Dermocybe group of webcaps, a set of small to medium species with dry, finely fibrillose caps and vivid pigments in yellow, orange, red and — in this case — green. True green is scarce among gilled fungi, so an olive-green webcap on the woodland floor is immediately arresting.

The whole fruitbody carries the pigment: the cap is dark olive to yellow-green, the gills start olive-green before rusty spores dull them, the stem is greenish-yellow and even the flesh is olive-tinted. The colours are anthraquinone pigments, the same chemical family that gives other Dermocybe species their reds and saffrons and has made the group a traditional source of natural dyes.

It is a woodland mycorrhizal species of acid soils, appearing with both broadleaves and conifers depending on the variety, and is one of the more distinctive webcaps a field mycologist can name confidently on colour alone.

Cap

Generally 2–6 cm across, convex then flattening, sometimes with a low broad umbo. The surface is dry and finely felted or minutely fibrillose-scaly, never viscid, and coloured dark olive-green, moss-green or yellow-green, often browner and duller at the centre with age.

Gills

Adnate, moderately crowded, olive-green to yellow-green when young — the key character — and gradually overtaken by rusty-brown spore colour to become olive-brown then rust. The gill edges stay greener longer than the faces. A yellowish-green cortina veils them in the button stage.

Stipe

3–8 cm tall and 4–10 mm thick, cylindrical or slightly thickened below, greenish-yellow to olive with fine longitudinal fibrils and often faint paler veil traces. It usually keeps more green than the cap does as the fruitbody ages, and rusty spore fall stains the veil zone.

Flesh & spore print

The flesh is olive-yellow to greenish, thin, with a mild or faintly earthy smell and no dramatic bruising change. The spore print is rusty brown, which contrasts strikingly with the green tissues; spores are ellipsoid to almond-shaped and warted.

Cortinarius venetus grows on the ground in woodland on acid soils, associating with beech, oak and birch in the typical form, while the variety montanus occurs with conifers, especially spruce, in upland and northern forest. It is found in leaf litter, moss and needle carpets, often in small scattered troops.

The season runs from late summer through autumn. The species is widespread but rather local across northern and central Europe, with additional records from conifer forests further north and in mountain areas, and it is generally treated as an uncommon find rather than an abundant one.

Like all webcaps this is an ectomycorrhizal fungus, sheathing the fine roots of its host trees and forming the Hartig net through which nutrients and carbon are exchanged. On the acid, leached soils it favours, the fungal partner is important in extracting nitrogen and phosphorus bound up in organic matter that tree roots cannot access directly.

The green anthraquinone pigments that colour every part of the fruitbody are of interest well beyond identification: Dermocybe webcaps as a group have been used historically for dyeing wool, and their pigment chemistry is one of the traits used to define the group taxonomically. The perennial mycelium persists in the humus layer, fruiting in the same patches over many seasons.

Other Dermocybe webcaps share the dry felted cap and slender build but differ in pigment: Cortinarius cinnamomeus is cinnamon-brown with yellow gills, C. croceus is olive-brown with saffron gills, and C. semisanguineus has an olive-brown cap with blood-red gills. Only C. venetus is green in the cap as well as the gills.

Cortinarius malachius and other violet-tinted webcaps can look greenish in poor light but have lilac rather than olive tones in fresh material. Outside the genus, green Tricholoma species such as T. equestre have white spore prints, no cortina and much thicker flesh, and green Russula species have brittle flesh and pale spore prints. A green mushroom with a rusty brown spore print is almost certainly this webcap.