Black Trumpet Identification Guide

The Setting and the Art of Seeing It

Black Trumpets are the classic example of a fungus that hides in plain sight. They fruit on the ground in mature broadleaf woodland, most reliably on mossy banks, in shallow depressions, along old woodland tracks and on the shoulders of stream gullies, under beech and oak in particular. The colour of the fruiting body is almost exactly the colour of wet leaf litter, so a dense troop can be invisible from standing height and obvious from a crouch.

The trick most people learn is to stop scanning for shapes and start scanning for holes. Because the fungus is a hollow funnel open at the top, what your eye actually catches is a scatter of small dark voids in the litter, like finger-holes punched in the ground. Once you have found one, stay still and keep looking at the same square metre. They come in dozens, often in tight overlapping clusters fused at the base, and the second and third finds are usually within an arm's reach of the first.

Reading the Fruiting Body from the Top Down

There is no cap in the ordinary sense. The whole fruiting body is a single trumpet, vase or cornucopia shape, typically three to twelve centimetres tall and two to eight centimetres across at the mouth. The upper rim flares outward and is markedly wavy, lobed and irregular, and it often splits or rolls with age. Look into the mouth: the inner surface of the funnel is the sterile upper face, and it is scurfy, minutely scaly or roughened, dark grey-brown to sooty black, becoming almost charcoal when wet and greying as it dries.

Run a fingertip down inside the funnel. The hollow continues all the way to the ground with no partition, so a lengthwise cut gives you two open half-tubes and nothing else. That continuous hollow is one of the defining structural features.

The Spore-Bearing Surface

Now turn the trumpet over and look at the outside of the funnel, because that is where the spores are produced. There are no true gills. The outer surface is smooth to shallowly and irregularly wrinkled, sometimes with faint blunt veins near the base that never resolve into thin, blade-like plates. Colour is ashy grey, grey-brown, or grey with a faint bluish or lilac cast, and it is conspicuously paler than the inner face, especially when the fungus dries and the exterior goes pale ash while the interior stays dark.

Press your thumbnail across those wrinkles. On a true Black Trumpet the surface deforms rather than tearing into separate plates, confirming that these are folds of the outer skin rather than gills.

Stipe, Base and Flesh

The trumpet tapers downward into a narrow stalk-like base, but the boundary is arbitrary because the tube continues to the very bottom. The base is often flattened, curved and grey-black, and it is frequently fused with two or three neighbours, so pulling one specimen lifts a small bouquet.

The flesh is thin, membranous and rather elastic rather than brittle, no more than a millimetre or two thick through most of the funnel wall. Cut it and nothing changes colour; there is no bruising reaction, no latex and no staining. That absence is itself diagnostic, because several dark look-alikes are rigid, brittle or gelatinous instead.

Taking a Spore Print

Spore printing is worth doing here because it separates the closely allied species. Choose a fully expanded specimen, trim the base, and lay the funnel on its side on white paper with the outer surface pressed down. Cover it with a cup and leave it overnight in a cool room. Because the deposit is pale, use white paper and then tilt it against the light to see the film.

Craterellus cornucopioides in the strict sense gives a white to pale cream or faintly buff print. Its close relative with a distinctly ochre, salmon or yellowish print is a separate taxon in most treatments, and the print is the cleanest way to tell them apart in the field kit. Under a lens the spores are smooth and broadly elliptical.

Substrate, Season and Ecology

This is a mycorrhizal fungus, forming root partnerships with broadleaf trees. Beech and oak are the classic hosts across its range, with hornbeam, chestnut and birch also recorded. It favours well-drained slopes with a thin litter layer, mossy banks and calcareous soils, and it comes up after summer and autumn rains, typically from midsummer to the first hard frosts.

Because it is mycorrhizal, it returns to the same patches for many years. Marking the location of a productive bank is far more valuable than searching new ground, and troops tend to expand slowly outward from the original spot rather than moving.

Separating It From Look-alikes on Morphology

Craterellus cinereus and its allies. These grey-black funnels look almost identical from above, but the outer surface carries distinct, narrow, blunt but clearly raised ridges that fork and run down the stalk, closer to a set of low false gills than to the smooth or shallowly wrinkled exterior of a true Black Trumpet. Look at the outside in raking light and the difference is clear.

Craterellus fallax. Structurally almost the same trumpet. The separator is the spore print, which is ochre to salmon rather than white to cream, and the exterior often shows a warmer, slightly ochraceous bloom in age.

Devil's urn, Urnula craterium. A spring fungus rather than a summer or autumn one, and a cup fungus rather than a funnel. It is a deep goblet with a thick, tough, rubbery wall, a fringed rim, a distinct short black stalk, and it grows attached to buried hardwood sticks. Its interior is the fertile surface, the opposite arrangement to a trumpet, and its wall is far too rigid to be mistaken once handled.

Dark forms of Cantharellus and Pseudocraterellus. Some small chanterelle relatives fruit in the same litter and can appear dark when wet. They differ in having a solid or only partly hollow stalk and well-developed decurrent false gills that are noticeably thicker and more regularly spaced than the shallow wrinkles of a Black Trumpet.

Blackened old specimens of other funnel fungi. Any candidate whose funnel is interrupted by a solid plug of tissue partway down, or whose underside carries true thin gills that separate cleanly when scraped, is not this species.

Quick Field Checklist

Hollow trumpet, open from rim to base; wavy lobed flaring mouth; scurfy dark inner face; smooth to shallowly wrinkled ashy outer face carrying the spores; thin elastic flesh with no colour change; white to cream spore print; mycorrhizal on the ground under beech and oak from midsummer to late autumn.