Dead man's fingersXylaria polymorpha

Dead man's fingers (Xylaria polymorpha) is a black fungus shaped like thick, knobbly fingers that poke up in tufts from the base of old broadleaved stumps. First Nature says they're often bent and look like arthritic black knuckles. Its Latin name polymorpha means 'many shapes': the fingers can be club-shaped, spindle-shaped, flattened, bent or fused. It has no cap, gills or pores; it's a tough body called a stroma, with tiny spore flasks sitting just under the surface. James Sowerby illustrated it in England in 1797 as 'the finger-like sphaeria'.

How do you identify dead man's fingers? The fingers are usually 3 to 8 cm tall, occasionally 10 cm, and 1 to 3 cm thick, with a rounded tip, narrowing below into a short, black, finely downy base attached to the wood. They grow in tufts of three to six, often bent. Young ones are greyish or pale brown, dusted with a pale powder of asexual spores, often with a paler tip. Mature ones are dark brown to black, dry and finely granular or wrinkled. They're hard and corky to woody to the touch. The best test is to cut one: inside, the flesh is snow-white and hard, under a thin black crust, with a single row of tiny black dots just beneath the crust. Those are the spore flasks. The spore print is black.

Where does it grow? On dead broadleaved wood, most often at the base of rotting beech and oak stumps, and on buried roots and logs. That's why it often seems to grow out of the soil, but it's always attached to wood underground. It slowly softens the wood from the base of the stump. The fingers last for months, so you can find them all year, though they're most noticeable from summer to mid-autumn.

Is dead man's fingers edible? No, it's hard and woody and isn't eaten. You may see headlines calling it 'as deadly as the death cap'. They go back to a single 2018 study from India that tested for toxins with a crude colour test, on material that was probably a different species. Nobody has confirmed it, but there's no evidence that it's safe either, so simply don't eat it.

This fungus also draws fine black lines in wood. Woodworkers prize this 'spalted' pattern, and dead man's fingers is one of the fungi used to create it on purpose.

What can you mistake it for? Candlesnuff fungus often grows on the same stumps, sometimes right next to it, but it's as thin as a pencil lead, 2 to 8 mm, forked like antlers, with white powdery tips in autumn. King Alfred's cakes is also black and grows on dead broadleaved wood, but it's a hard ball 2 to 8 cm across with concentric rings inside. Outside our catalogue, the closest lookalike is dead moll's fingers (Xylaria longipes): slimmer and smaller, 0.5 to 1.5 cm thick, with a distinct narrow stalk, mostly on sycamore. Black earth tongues (Geoglossum, Trichoglossum) grow directly on the ground in old grassland, not on wood, and have a flattened, tongue-like head. Burnt wood and charcoal are black right through, while dead man's fingers is white inside.