Black Trumpet

Black Trumpet (Craterellus cornucopioides) is among the most unusual-looking of the larger woodland fungi. The whole fruiting body is a single thin funnel, hollow from the flared, wavy mouth right down to the base, so that it resembles a small ragged trumpet or the horn of a gramophone pushed up through the leaf litter.

Craterellus sits in the Cantharellales alongside the true chanterelles and shares their basic construction: instead of gills or pores, spores are produced across a smooth or gently folded outer surface. In the Black Trumpet this surface is almost featureless when young, developing only shallow veins and wrinkles with age, which is the simplest hymenium of any commonly encountered woodland fungus.

Its fame among naturalists rests on how difficult it is to spot. The dark grey-black colouring, matt texture and thin outline blend perfectly into shaded leaf litter, and observers frequently walk through a large troop without registering it. Once one fruiting body is seen, dozens usually become visible in the same square metre, since the species fruits gregariously in tight, overlapping clusters.

Fruiting body

There is no separation into cap and stipe in the usual sense. The whole structure is a trumpet or deep vase, 3-12 cm tall and 2-8 cm across the mouth, hollow all the way to the narrow base. The mouth is flared, wavy, irregularly lobed and often split, with the margin rolled slightly outward.

Inner surface

The inner (upper) surface lining the funnel is sterile and the darkest part of the fungus: dark grey-brown, sooty brown or nearly black, and distinctly scurfy or minutely scaly, especially toward the centre. It is often paler and browner in dry weather and much darker when wet.

Outer surface

The outer surface carries the spore-producing layer. It is ashy grey to grey-brown, paler than the inside, and usually smooth or only shallowly wrinkled, sometimes with faint blunt veins running down toward the base but never with distinct blades or gill-like folds. Older specimens may take on a whitish bloom as the spores mature.

Flesh & spore print

The flesh is very thin, membranous, greyish and brittle, tearing easily. The spore print is white to pale cream, best obtained by standing a trumpet mouth-down on dark paper for several hours.

Black Trumpet is a mycorrhizal fungus of broadleaved woodland, most strongly associated with beech and oak, and also recorded with hornbeam, sweet chestnut, lime and hazel. It favours deep, undisturbed leaf litter on mossy banks, along shaded slopes and hollows, and it shows a marked preference for calcareous or at least base-rich soils, though it is not strictly confined to them.

Fruiting occurs from midsummer through autumn, typically peaking after prolonged rain in late summer. The species is widespread across Europe, in parts of temperate Asia, and in eastern North America, where a closely related complex of similar dark trumpets occurs and has been divided by some authors into several species based on subtle differences in hymenium wrinkling and spore size.

The Black Trumpet forms ectomycorrhizal associations, sheathing the fine root tips of its host trees and exchanging soil-derived phosphorus, nitrogen and water for sugars produced by the tree. Because of this partnership it cannot be cultivated on dead substrate in the way that wood-rotting fungi can, and its presence indicates a mature, relatively undisturbed woodland root system.

The mycelium is long-lived and forms extensive underground networks, which is why fruiting bodies emerge in dense repeating troops in the same spots year after year, often in near-identical arcs of litter. The thin fruiting bodies dry and shrivel rather than rotting, and dried specimens can persist for weeks on the woodland floor while continuing to release spores.

Craterellus cinereus (and the closely related C. cornucopioides var. sinuosus) is the nearest match, differing in having distinctly raised, branching, grey wrinkled ridges on the outer surface rather than a nearly smooth one. Yellowfoot (Craterellus tubaeformis) shares the hollow trumpet form but is much paler, with a yellow-brown to olive-brown cap, a conspicuously yellow hollow stipe, and clear blunt grey-blue decurrent folds on its outer surface. Craterellus lutescens is similar again but with an almost smooth orange-yellow underside.

Among unrelated fungi, the Devil's Urn (Urnula craterium) can superficially resemble a black trumpet but is a tough, leathery goblet with a distinctly rimmed mouth, grows directly on fallen hardwood branches rather than out of soil, and appears in early spring. Dark Helvella species have a stalked, saddle-shaped or lobed head rather than an open hollow funnel.