Dead Man's Fingers Identification Guide

The Scene You Find It In

Dead Man's Fingers announces itself before you can name any structure on it. You are usually in shaded, humid broadleaved woodland, standing over a long-dead stump of beech, elm, maple or ash, or over the collapsed remains of a root plate. Out of the rotting wood, or straight out of the soil above buried roots, rises a cluster of blunt black clubs. They look less like a mushroom than like something left behind, and their stiff, upright, slightly splayed arrangement is exactly what gives the species its name.

The important first note is that these clubs are attached to wood, not to loose litter. Trace one down with a knife or your fingers. It will run to a stump base, an old buried root or a partly decayed log; if it appears to come from bare soil, dig a little and you will find wood underneath.

What You Are Actually Looking At

This is not a gilled fungus at all. Xylaria polymorpha belongs to the flask fungi, and the black finger you are holding is a stroma, a dense mass of fungal tissue whose outer layer houses hundreds of tiny embedded spore flasks called perithecia. Understanding that changes how you examine it: instead of hunting for gills and a ring, you are reading shape, surface texture, crust thickness and internal structure. The whole thing is tough, corky and unyielding rather than fleshy, and it will bend before it breaks.

Working Through the Shape

Mature fingers are typically 3 to 10 cm tall and 1 to 3 cm thick, club-shaped to irregularly cylindrical, often flattened, lumpy or lobed, and sometimes fused in pairs. The tip is characteristically rounded and blunt, never drawn out into a fine point. Below, the club narrows into a short, ill-defined stalk-like base that is usually hidden in the wood.

The species is well named for its variability. Some clusters are fat and stubby, almost like burnt potatoes standing on end; others are longer and more finger-like. What stays constant is the blunt tip, the substantial thickness relative to height, and the sense that the club is solid rather than hollow.

The Surface Through a Lens

Young stromata are the odd ones out. They emerge pale, greyish to bluish or brownish, with whitish powdery tips, because the fungus first produces asexual spores as a fine dust over the growing surface. Collectors often fail to match these pale, club-tipped juveniles with the black adults nearby.

As the stroma matures the surface darkens to a matt brownish-black or coal-black and becomes finely roughened. Put a lens on it. You should see a low, pimpled or warted texture with tiny raised dots, each dot the ostiole, the mouth of one buried perithecium. In fresh material the surface may crack into fine plates. That warted, dotted, non-shiny crust separates Xylaria from the smooth, varnished stromata of unrelated black fungi.

Cutting One Open

A cross-section is the single most convincing character in the field. Slice a finger across with a sharp knife. You will see a hard black outer rind perhaps a millimetre thick and, inside it, a striking chalk-white to greyish, firm, fibrous interior. Just beneath the rind, a neat ring of small dark cavities is visible where the perithecia sit embedded in the outer layer, each connected to the surface by a fine neck. That contrast between a black crust, a ring of dark flask cavities and a white core is unmistakable and holds even in old, weathered material.

A longitudinal cut shows the same white flesh running the length of the club and narrowing into the base. Nothing changes colour on cutting, and the flesh does not exude latex or liquid.

Spores Without a Conventional Print

You cannot lay this fungus gill-side down on paper, but you can still collect a deposit. Take a mature blackened club, stand it upright on a slip of white card or glass in a covered container overnight, and check the surface in the morning; ripe stromata shed a fine sooty deposit around the base. Alternatively, place the card against the side of the club.

Under the microscope the spores are large, blackish-brown, spindle-shaped with pointed ends and slightly bent, usually 20 to 32 by 5 to 9 micrometres, each with a straight germ slit running most of the spore length. Size and shape here are genuinely diagnostic within the genus, since the closest relatives differ mainly in spore dimensions.

Substrate and Season

Xylaria polymorpha is a wood-decay fungus of hardwoods, breaking down the structural components of dead trunks, stumps and roots and producing a soft rot. Beech, elm, maple, ash, oak and orchard trees are all frequent hosts; conifers are unusual. It also colonises long-buried roots, which is why fingers sometimes appear to grow out of open soil in a wood or old orchard.

The stromata are extremely persistent. They begin appearing in late spring and early summer as pale clubs, mature and blacken through summer and autumn, and can stand recognisably through winter into the following year, weathered and hollowing but still showing the white interior when cut. This means the fungus can be identified in any month, unlike most fleshy species.

Separating the Close Look-alikes

Xylaria longipes is the main confusion. It is a slimmer species, generally under 1.5 cm thick, with a longer and much better defined stalk that is often distinctly narrower than the fertile head, giving a genuine club-on-a-stem outline. Its favoured host is sycamore and other maples, and its spores are considerably smaller.

Xylaria hypoxylon is unmistakable once seen: thin, flattened, antler-branched or awl-shaped, with white powdery tips for much of its life, usually only a few millimetres wide.

Kretzschmaria deusta produces a brittle black crust hugging the wood surface rather than upright fingers, and is grey and lumpy when young.

Old, blackened Cordyceps and related club fungi arise from buried insects or from other fungi rather than from wood, and are usually brightly coloured rather than black.

Podostroma and Trichoderma clubs are paler and softer, and lack the hard black rind over a white core.

Field Checklist

Upright black clubs 3 to 10 cm tall with blunt tips, tough corky texture, a finely warted and dotted surface, a hard black rind over a chalk-white interior with a ring of perithecial cavities beneath the crust, attachment to dead hardwood or buried roots, and long persistence across the year. Together those points confirm Dead Man's Fingers.