Blackening Waxcap
Hygrocybe conica
Also called witch's hat, conical waxcap, blackening wax cap
A sharply conical orange to scarlet waxcap that turns inky black wherever it is bruised or as it ages, ending as a wholly charred-looking fruit body.
Overview
The Blackening Waxcap is the one grassland waxcap almost anyone can name, because of the way it dies. The fresh fruit body is a sharply pointed cone in flame orange, scarlet or lemon yellow; touch it, and within minutes the spot goes grey then black. Left alone, the whole mushroom blackens progressively from the margin and stem base until it stands in the turf like a small burnt taper, still holding its conical shape.
It sits in Hygrocybe, the waxcaps, distinguished by soft, thick, waxy, distant gills and a white spore print. H. conica is treated by many mycologists as an aggregate rather than a single tidy species, with a swarm of closely related forms and segregates — H. conicoides of sand dunes, H. singeri with a viscid stem, H. nigrescens with broader caps — separated on subtle differences in cap shape, gill colour and habitat.
Unlike most of its relatives it is not fussy about habitat, turning up on mown lawns, road verges, dunes and woodland tracks as well as in the ancient grassland that the rarer waxcaps demand, which makes it by far the most frequently encountered member of the genus.
How to identify it
Cap
Acutely conical, sometimes almost spike-like, later expanding to a broad cone with a persistent sharp umbo, 2–7 cm across. The surface is slightly greasy to viscid when wet, silky-fibrillose when dry, and coloured bright orange, scarlet, orange-red or clear yellow. The margin is often lobed, splitting radially, and blackening begins there and at the stem base before spreading over the whole fruit body.
Gills
Free to narrowly adnexed, broad, thick, waxy and moderately crowded for a waxcap. They start whitish to pale yellow, become yellow-orange, and blacken along the edges as the mushroom ages or after handling.
Stipe
Cylindrical, 4–10 cm tall, often twisted and longitudinally grooved or fibrous, yellow to orange with a whitish base, hollow and fragile. No ring and no volva. It blackens readily, usually beginning at the base and working upwards.
Flesh and spore print
The flesh is thin, yellowish and brittle, and turns grey then black on exposure and bruising — the single most useful field character. The spore print is white; spores are smooth and ellipsoid. Fully blackened old fruit bodies remain firm and persist in the turf for some time.
Where and when it grows
Far less demanding than most waxcaps, it grows in all kinds of short grassland: garden lawns, playing fields, road verges, churchyards, upland pasture, coastal dunes and grassy woodland rides. It tolerates a wider range of soil fertility and disturbance than its relatives, which is why it is often the first waxcap to appear at a new site.
The season is long, from mid-summer through to the first hard frosts, with the main flush in autumn. Distribution is essentially cosmopolitan: it is recorded across Europe, North America, Asia, Australasia and southern South America, although some of those records probably belong to segregate species within the H. conica aggregate.
Ecological role
Like other grassland waxcaps it is not a wood or litter decomposer in the ordinary sense. Its mycelium lives in the upper soil in close association with grassland plants and mosses, and stable isotope evidence suggests a biotrophic relationship rather than free-living saprotrophy. It has resisted routine laboratory cultivation on standard substrates.
The blackening itself is an oxidative browning reaction in the flesh, comparable in principle to the darkening of cut fruit, and it advances steadily once the tissue is damaged or begins to senesce. Fruiting follows autumn rain, and the same patches of turf typically produce fruit bodies in the same spots for many successive seasons.
Similar species
Within the aggregate, Hygrocybe conicoides is a dune specialist with a duller brick-red cap and, crucially, orange to blood-red gills; Hygrocybe nigrescens has a broader, less acutely pointed cap and a paler stem; and Hygrocybe singeri has a distinctly viscid, slimy stipe. All blacken, so the separation rests on cap shape, gill colour and habitat.
Among non-blackening reds, Hygrocybe coccinea is smooth, scarlet and rounded rather than pointed, and Hygrocybe punicea is much larger with a coarsely fibrous stem and a white base — neither turns black. Small conical yellow species such as Hygrocybe acutoconica keep their bright colour to the end and merely fade. Any grassland waxcap that goes grey-black at a fingerprint belongs to this group.