Scaly Wood Mushroom

Agaricus langei, the Scaly Wood Mushroom, is the largest and most strongly reddening member of the woodland Agaricus group in Europe. Named for the Danish mycologist Jakob Lange, it stands taller and heavier than its close relatives, with a cap densely covered in flat, dark reddish-brown fibrous scales over a paler ground.

It belongs to Agaricus section Sanguinolenti, the "bleeding" wood mushrooms, all of which share the striking property of turning red rather than yellow when the flesh is damaged. In A. langei this reaction is unusually fast and intense: a cut through the stipe develops a deep blood or brick red within half a minute and eventually darkens to brown.

Unlike the meadow mushrooms, this is a forest fungus, tied to accumulations of needle and leaf litter in shaded woodland rather than to grassland. It fruits mainly under conifers, especially spruce, and its combination of size, dark scaly cap, and instant reddening makes it one of the more satisfying woodland Agaricus species to name in the field.

Cap

Generally 6–12 cm across and occasionally larger, at first cylindrical to barrel-shaped, then convex and finally broadly flattened. The whole surface is covered in flat, appressed, radially arranged fibrillose scales of a dark reddish-brown to chestnut colour, densest at the centre and slightly separating toward the margin to reveal a paler cream ground beneath. The overall impression is of a shaggy, uniformly brown cap rather than a spotted one.

Gills

Free from the stipe and very crowded. They are pale greyish-pink at first, then a clean dull pink, before darkening steadily through purplish brown to a deep chocolate brown. Cut or damaged gill edges also redden.

Stipe

Tall and fairly slender relative to the cap, 8–15 cm long and 1–2 cm thick, cylindrical with a slightly swollen but not marginate base. It is white and smooth, staining red where handled, and carries a large, thin, pendulous white ring in the upper third; the ring's underside is smooth to faintly cottony and it can collapse against the stem with age.

Flesh and spore print

White and moderately thick, turning vivid blood-red within seconds of being cut — the single most reliable field character — and slowly ageing to a dull brownish red. The odour is mild and mushroomy, without almond or ink notes. The spore print is dark brown; the spores are noticeably larger than those of related wood mushrooms.

A woodland species of deep litter and humus. It is most frequent under conifers, particularly spruce, but also occurs in mixed and deciduous woodland, on shaded woodland tracks and rides, and in mature conifer plantations and parkland where a thick needle layer has built up. It favours nutrient-rich, well-drained soils and is often found on slightly disturbed ground such as path margins and banks.

The season runs from late summer into autumn, peaking after the first substantial rains that follow warm weather. Fruit bodies emerge singly, in scattered groups, or in short arcs. The species is widespread through northern and central Europe and is reported patchily elsewhere in the temperate northern hemisphere.

Like all its relatives, Agaricus langei is a saprotroph and forms no mycorrhizal partnership with the trees it grows beneath. Its mycelium spreads through the fermentation and humus layers of the forest floor, decomposing fallen needles, leaves, and fine roots. Conifer litter is comparatively resistant to decay, so litter specialists like this one play a significant part in preventing needle build-up and in returning nitrogen and minerals to the rooting zone.

The reddening reaction is caused by the rapid oxidation of compounds in the flesh once cell walls are ruptured and air reaches them — the same broad class of process that browns a cut apple, but far more colourful. Fruit bodies are relatively long-lived for the genus and are frequently grazed by slugs and fungus gnat larvae, which help distribute spores through the litter layer.

The Blushing Wood Mushroom (Agaricus sylvaticus) is the closest relative and also reddens, but it is distinctly smaller and more slender, its cap scales are paler and greyer brown, and the colour change is slower and duller. Agaricus sylvicola, the Wood Mushroom, shares the woodland habitat but is wholly white to cream with a smooth silky cap, turns yellow rather than red, and smells strongly of aniseed.

The Prince (Agaricus augustus) is another large brown-scaled woodland species, but its scales are golden to tawny brown on a paler ground, it yellows rather than reddens when rubbed, it has a powerful almond odour, and its ring underside is conspicuously cogwheel-patterned. Various Lepiota and Chlorophyllum species have scaly caps too, but keep white or greenish gills and produce a white or green spore print instead of chocolate brown.