Greenfoot Fibrecap

Greenfoot Fibrecap is one of the most immediately recognisable species in a difficult genus, thanks to a single startling character: the base of its stipe is stained a strong blue-green or verdigris colour, quite unlike anything else among the small brown fibrecaps. Slicing a fruitbody lengthwise reveals the pigment running through the lower stipe tissue.

The rest of the fungus is dark and shaggy. Both the cap and the stipe are clothed in coarse, upcurved fibrillose scales, giving a bristly, almost woolly appearance that the epithet calamistrata, meaning curled with tongs, describes neatly. The upper stipe often shows reddish tones and the flesh in the stipe frequently flushes reddish where cut, contrasting sharply with the green base.

It is a species of cool, damp coniferous habitats, favouring mossy spruce and pine forest, boggy margins and Sphagnum fringes, and is most frequent in boreal and montane regions.

Cap

1.5–4 cm across, convex to bell-shaped with a low umbo. Dark brown, umber or chocolate, dry, and densely covered in coarse recurved fibrillose scales that give a shaggy or bristly outline, particularly toward the centre. The margin is often ragged and may carry fine pale veil fibrils when young.

Gills

Adnexed, moderately crowded, pale grey-brown to clay when young and maturing to a darker olive or umber brown. The edges are noticeably paler and minutely fringed.

Stipe

3–7 cm tall and 3–7 mm thick, cylindrical and equal, without a bulb. It is dark brown and densely covered in the same coarse recurved scales as the cap, often with a reddish tinge in the upper part. The lowest centimetre or two is a striking blue-green to verdigris, both on the surface and internally.

Flesh and spore print

Flesh is pale brown in the cap and reddish in the stipe, with blue-green pigment concentrated at the base. The odour is faint, sometimes slightly fishy or earthy. The spore print is dull brown, and the spores are smooth and ellipsoid to bean-shaped.

Greenfoot Fibrecap grows on damp acid soil among mosses in coniferous and mixed woodland, especially with spruce and pine, and is often found at the edges of bogs, in wet flushes, along stream banks and among Sphagnum or feather mosses. It also occurs with birch in damp mixed stands.

It fruits from summer into autumn, usually singly or in small scattered groups. The species has a boreal to montane distribution, being widespread in northern Europe, Scandinavia, upland Britain, Canada and the northern United States, and becoming scarce in lowland and southern regions.

This is an ectomycorrhizal fungus, forming root sheaths mainly with spruce, pine and birch. In the cool, waterlogged, acid soils it favours, mineral nitrogen is often locked in slowly decaying organic matter, and mycorrhizal partners like this one are essential in mobilising it and delivering it to the trees in exchange for photosynthetic sugars.

The blue-green pigment in the stipe base is unusual among gilled fungi and appears to be produced in the tissue closest to the mycelium rather than being taken up from the substrate. Its function is unknown, but such pigments in fungi are often linked to interactions with soil bacteria and invertebrates. Fruitbodies are ephemeral and decay quickly in the humid habitats where the species grows.

Inocybe lacera shares the shaggy dark cap and disturbed sandy habitat but has a plain brownish stipe base with no trace of blue-green, and its spores are long and cylindrical. Inocybe cincinnata is smaller with violet tones at the stipe apex and lacks green pigment entirely.

Among other scaly brown woodland agarics, Pholiota species have viscid caps and rusty-brown spore prints, and Tubaria species are much frailer with smooth hygrophanous caps. No other fibrecap in the same habitat combines a densely scaly stipe with a verdigris base, so a lengthwise cut through the stipe usually settles the matter at once.