You’re walking through the woods on a crisp, late October afternoon, smelling the sharp scent of decaying leaves and listening to the dry rustle of beech leaves in the breeze. You decide to take a break, sit on an old stump, munch an apple and observe this amazing world…but, what is that reaching up next to your comfortable seat – is it a hand from beyond the grave?! Black fingers with swollen knuckles are stretching up through the leaf litter to grab hold of your boots! You leap onto to your trusty stump to escape the oncoming zombie apocalypse (you knew, deep down, it was inevitable). When the decrepit hand makes no forward movement and no retreat, you summon your courage for a closer look and you uncover: the Dead Man’s Finger mushroom (Xylaria polymorpha).

The Dead Man’s Finger is an ascomycetous fungus (producesspores in sac-like cells called ascus), and goes through a few costume changes from spring through late fall and early winter. Individual “fingers,” or club-shaped structures, are commonly found in groups of at least three to six and emerge in the spring. Initially, these fingers, or communal fruiting bodies that are also called stroma, are just a few inches long, white to dark grayish in color and the conidiaspores concentrate at the “fingertips” during this asexual reproductive stage. The conidia are blown or washed away as the mushrooms mature.

Photo of the fungus, Dead Man's Fingers (Xylaria polymorpha)

Photo credit: James Murray.

As the stroma grow throughout the summer and fully mature in fall and early winter, the fingers can grow several more inches, darkening to dark brown and black, sometimes with greenish or bluish tinges. If you cut the stroma open lengthwise, the hard, white flesh eerily resembles bone inside of mummified skin. During this sexual reproductive phase, the ascospores are produced in spore-producing cavities called perithecia, near the surface of the “skin.” A black spore print confirms presence of this spooky spectre.

Photo of the fungus, Dead Man's Fingers (Xylaria polymorpha)

Photo credit: New Hampshire Garden Solutions.

Beech, maple, elm, locust and apple stumps serve as likely headstones for these saprotrophic fungi, which only feed on dead and dying trees. This wood-rotting mushroom specializes in consuming polysaccharides (like glucan) that bind cellulose and lignin together to form wood, and leaves a wake of nutrient-rich, mushy material for invertebrates and other creepy-crawlies to feed on.

Experts do not recommend using mulch chipped from tree stumps or roots infected with Dead Man’s Finger. It can cause black root rot in apple trees, with X. polymorpha infections more common in the eastern U.S. and X. mail more common in the southern Appalachians.

All members of Xylaria contain some level of amatoxins and phallotoxins – the same compounds found in some of the most dangerous mushrooms in the world. As a result, Dead Man’s Finger is not considered an edible fungus, unless you want to end up six feet under.