Copper Brittlegill

The Copper Brittlegill, Russula decolorans, is one of the most reliably recognisable members of a notoriously difficult genus. Russula is a large group of ectomycorrhizal agarics whose flesh is built from rounded, loosely packed cells (sphaerocysts) rather than long fibrous hyphae, which is why the whole fruiting body snaps cleanly like a stick of chalk instead of tearing into strands. Brittlegills also lack a ring, lack a volva, and never exude latex when cut, which separates them at a glance from Amanita and from their close relatives the milkcaps, Lactarius.

What sets R. decolorans apart within the genus is not its colour, which is a fairly ordinary orange to coppery brown, but the way its tissues change over time. Cut or simply aged flesh passes through a dull grey stage and eventually goes almost black, and the stipe of a mature specimen is often mottled ash-grey along its length. This greying reaction, combined with a boreal conifer habitat, narrows the field enormously.

It belongs to the Russulaceae, a family that also contains Lactarius and Lactifluus, and it is a characteristic species of northern and montane forests where pine and spruce dominate. In Fennoscandia and Canada it is one of the commonest large brittlegills of bilberry and moss-carpeted pine woodland.

Cap

The cap is 5–12 cm across, at first hemispherical and later flattening or shallowly depressed at the centre. Colour is a warm orange to brick or copper brown, typically darkest in the middle and paler toward the margin, and it fades noticeably in sun and rain to dull ochre or tan. The surface is smooth, slightly greasy in wet weather and matt when dry, and the cuticle peels back roughly a third to half of the radius. The margin is smooth in young caps and becomes faintly grooved as the spores mature.

Gills

Gills are adnexed to almost free, moderately crowded, fairly brittle, and pale cream at first, deepening to a soft ochre as spores develop. With handling and age they take on grey then blackish stains, most obvious along the edges and where slugs have grazed.

Stipe

The stipe is 5–10 cm tall and 1.5–3 cm thick, cylindrical or slightly club-shaped, white when young and quickly becoming grey-mottled from the base upward. It is stuffed then hollowing, without a ring and without a bulb or sac at the base. The surface is faintly wrinkled lengthwise.

Flesh & spore print

Flesh is white and firm, greying within minutes to an hour of being cut and eventually going charcoal-black in old or waterlogged specimens. There is no milky exudate. The spore print is pale ochre, and the spores are warty with a partial network under the microscope.

Russula decolorans is a species of acidic, nutrient-poor conifer forest, most abundant under Scots pine and also found with spruce. It favours mossy or bilberry-dominated ground, peaty margins of bogs, and open sandy pine heath, and it can fruit right out of Sphagnum at the edge of mires. Rich or strongly calcareous soils are not its habitat.

It is a northern species, common through boreal and montane Europe from Scandinavia and the Baltic states through the uplands of central Europe, and widespread across northern North America in comparable pine and spruce forest. Fruiting runs from midsummer through autumn, peaking after late-summer rains, and it is often one of the last large brittlegills still appearing as the season closes.

Like all brittlegills, the Copper Brittlegill is ectomycorrhizal. Its mycelium sheathes the fine root tips of pine and spruce, forming a mantle and an inward-growing Hartig net between root cells through which mineral nutrients and water are traded for tree-derived sugars. In the thin, acidic, often waterlogged soils where it thrives, this partnership does much of the work of nutrient capture that the tree roots alone could not manage.

The fruiting bodies are short-lived and heavily used by forest invertebrates and small mammals, which fragment them and disperse spores. Because the mycelium is long-lived and tied to living hosts, the species is a good indicator of mature, undisturbed conifer stands, and it disappears from ground that has been cleared or heavily fertilised.

Russula paludosa shares the boreal conifer habitat and reddish tones but is usually a cleaner red or blood-red, is often much larger, and crucially does not grey — its flesh stays white and its stipe often carries a pink flush instead of ash-grey mottling. Russula claroflava, the Yellow Swamp Brittlegill, also greys strongly when cut, but its cap is a bright chrome to egg-yellow rather than copper, and it grows with birch in wet ground rather than with pine.

Russula vinosa (R. obscura) greys in much the same way but has a wine-purple to dark red cap. Among the milkcaps, several Lactarius species of pine woods look superficially similar in colour, but any milkcap will bead a droplet of latex from broken gills, which no brittlegill ever does.