Candlesnuff Fungus

Candlesnuff Fungus is an ascomycete in the family Xylariaceae, a group of tough, carbon-black wood decayers that also includes King Alfred's Cakes (Daldinia) and the dead man's fingers (Xylaria polymorpha). Rather than producing a soft, short-lived mushroom, Xylaria hypoxylon builds a hard, almost woody stroma that persists on a log for months and often survives right through winter.

What makes the species instantly recognisable is its two-tone appearance. Young fruitbodies are coated in a white to greyish powder of asexual spores (conidia), concentrated at the branching tips, while the base is already matt black and slightly velvety. The effect is a blackened wick with a pale glowing point, which is exactly where the common name comes from.

As the season advances the white bloom is shed and the clubs turn wholly black and minutely pimpled, because the sexual stage develops flask-shaped chambers (perithecia) just beneath the surface. Because the two phases look so different, the same species is often recorded twice by beginners: once as a white-tipped antler in autumn and once as a plain black finger in late winter.

Fruiting body

Upright, flattened or cylindrical clubs 2-6 cm tall and only 2-8 mm wide, usually simple but frequently forked once or twice near the top into antler- or hand-like branches. They arise singly or, far more often, in dense troops from the same piece of wood.

Surface and colour

The lower half is matt black to dark grey and finely velvety or downy. The upper half and tips are covered in a chalky white to pale grey powder in young specimens. With age the white coat wears away and the whole club becomes black, hard and roughened by tiny raised bumps, each a perithecium opening by a minute pore.

Flesh & spore print

The interior is tough, fibrous and pure white, contrasting sharply with the black rind - a good confirmatory feature when a club is sliced lengthways. The clubs are pliant rather than brittle and do not shrink much on drying. The sexual spores are black, bean- to spindle-shaped and produce a black print; the earlier conidial stage gives the white surface dust.

Xylaria hypoxylon grows on dead hardwood: stumps, fallen branches, sawn log ends, buried roots and worked timber lying on the ground. Beech, birch, oak, ash and hazel are all frequent substrates, and it will colonise woodchip mulch and old fence posts in gardens and parks. It occasionally appears on conifer wood but is far less common there.

Fruiting is essentially continuous, with new white-tipped clubs appearing from midsummer onwards and blackened old clubs persisting all winter. It is widespread and abundant across Europe, North America, temperate Asia and Australasia, and is one of the first fungi most people notice when learning to look at dead wood.

The species is saprophytic, breaking down the lignin and cellulose of dead hardwood and contributing to a soft white rot in the outer layers of stumps and branches. Its dark, carbonised stroma is a protective structure that lets the fungus hold its position on exposed wood through drought and frost, releasing spores over a very long window rather than in one short flush.

The two spore stages divide the work: powdery conidia are shed dry from the white tips and dispersed by air currents and passing invertebrates over short distances, while the later ascospores are forcibly discharged from the perithecia in damp weather. Colonised wood is gradually softened, opening it up to beetles, springtails and secondary fungi, so the species is an early and persistent player in stump decomposition.

Dead Man's Fingers (Xylaria polymorpha) is much stouter - fingers 1-3 cm thick, club-shaped and swollen, usually unbranched, and lacking the persistent white tips. Dead Moll's Fingers (Xylaria longipes) is intermediate, with a distinct slender polished stalk and a smooth cylindrical head on fallen sycamore and maple branches.

The stagshorn jelly fungi (Calocera viscosa and C. cornea) share an antler outline but are bright orange-yellow, gelatinous-rubbery and elastic rather than hard and black. White coral fungi (Clavulina) are pale throughout, brittle and never have a black base. Young Xylaria hypoxylon is also confused with white Tremella or mould-covered twigs, but slicing a club reveals the diagnostic white core inside a black rind.