Devil's Cigar

The Devil's Cigar (Chorioactis geaster) is one of the most geographically peculiar fungi known, restricted to a small number of counties in north-central Texas and, on the other side of the world, to a handful of sites in Japan. Nothing quite like it grows in between, and the disjunction has made it a favourite subject for studies of fungal biogeography.

Before opening, the fruit body looks like a dark brown, velvety cigar or spindle standing on a short buried stalk. At maturity it splits from the tip downward into four to seven stiff, tapering rays that curl back to form a star, revealing a pale cream to tan inner surface. The opening is sometimes accompanied by an audible hiss as spores are released in a visible puff.

Despite its star shape it is not related to the earthstars, which are basidiomycete puffball relatives. Chorioactis is an ascomycete in the family Chorioactidaceae, a small group of leathery cup fungi, and its spores are produced in asci that line the inner surface of the rays.

Unopened fruit body

A dark brown to blackish, cigar- or torpedo-shaped body 4-12 cm long and 1-4 cm thick, tapering at both ends, with a dry, densely velvety to shaggy, felted surface. It stands more or less upright on a short, tough, partly buried stalk-like base.

Opened fruit body

Splitting from the apex, it opens into 4-7 rays that flex outward and downward into a star up to 10-13 cm across. The rays are leathery and stiff, brown and hairy on the outside, and pale cream, buff or tan and smooth on the inside.

Inner surface

The pale inner face of each ray is the hymenium, where the asci sit. It is smooth to slightly wrinkled and may darken to ochre or greyish as the spores mature and are shed.

Flesh and spores

The tissue is tough, leathery and fibrous rather than fleshy or gelatinous, and does not change colour when cut. Spores are large, smooth and elliptical, giving a whitish deposit; a synchronised discharge can produce a small visible cloud when the fruit body opens.

In Texas the fungus is associated almost exclusively with dead cedar elm (Ulmus crassifolia), fruiting from buried dead roots and the bases of decaying stumps, usually in ravines, along creek terraces and on shaded slopes with deep leaf litter. A few records involve other hardwoods.

In Japan, where it is called kirinomitake, it grows on dead oak (Quercus) and occasionally on dead Paulownia, in similar humid, shaded, sloping sites. Fruiting in both regions is in the cool season, roughly October through April in Texas, with fruit bodies appearing individually or in small clusters directly from the soil above buried wood.

Chorioactis geaster is saprophytic, decaying the buried dead roots and stumps of its host trees. The mycelium remains hidden in wood below ground for long periods, and fruiting is sporadic, which combined with a very narrow range makes it a genuinely uncommon find.

The star-shaped opening is a dispersal mechanism: splitting exposes a large area of spore-bearing surface well above the litter, where drying and air movement can carry the discharged spores away. The tough, weather-resistant rays remain recognisable for weeks after the spores have gone, gradually curling and blackening.

True earthstars (Geastrum species) also open into a star of rays, but they are puffballs: the star surrounds a papery spore sac with a central pore, and their interior fills with a powdery brown spore mass rather than presenting a smooth pale spore-bearing surface. Astraeus barometer earthstars behave similarly, with thick hygroscopic rays that open and close with humidity.

Urnula craterium, the devil's urn, shares the leathery texture, dark colour and cool-season fruiting on hardwood but stays as a deep goblet or urn with a ragged rim rather than splitting into rays. Unopened Devil's Cigars can suggest a small stinkhorn egg on a stalk, but stinkhorn eggs are smooth, whitish and gelatinous inside, while Chorioactis is dry, fibrous and dark brown throughout.