Beech Woodwart

Description

Beech woodwart is a hard, carbonaceous little fungus that forms small, hemispherical or flattened bumps on dead wood, usually 2–9 mm across. Young ones are rusty red and covered with tiny mounds; with age they darken to brown and blackish brown. The bumps often grow together into irregular clusters.

It grows on dead trunks, stumps and branches of broadleaved trees, most often beech, and is common in Poland. It can be found all year round.

It is hard to tell apart from other woodwarts with the naked eye; the closest, Hypoxylon howeanum, has a smoother surface, and a reliable distinction requires a microscope. It is inedible: it has hard, carbonaceous flesh and no culinary value.

Identification features

Cap

The fungus does not form a cap but a fruiting body in the form of a cushion-like stroma. The stroma is nearly round or hemispherical, flattened; a single one is 2–9 mm in diameter (up to 15 mm according to some descriptions) and 1.5–7 mm high. Neighbouring stromata often fuse into irregular clusters. The surface is rusty red (reddish when young), uneven, covered with perithecial "mounds" (about 15–25 at maturity). Older stromata gradually turn brown: from rusty to brownish red, brown, and finally blackish brown.

Hymenophore (underside of the cap)

No typical hymenophore. The spore-bearing asci are in perithecia embedded in the stroma; the ostioles are black, lying level with the stroma surface or slightly sunken. The perithecia are ovoid, 0.25–0.38 mm in diameter and 0.45–0.65 mm high.

Stem

Absent; the stroma sits directly on the substrate.

Flesh

Beneath the surface of the stroma there are orange-red granules; below the perithecia the core is black, hard and carbonaceous. In KOH the fruiting body releases orange pigments. Smell and taste have no diagnostic significance; the flesh should not be tasted.

Spore print and spores

Spores (ascospores) dark brown, ellipsoid, inequilateral, often crescent-shaped, 10–15 × 4.8–6.8 µm. Asci cylindrical, 135–180 × 7–10 µm. Spore print colour: no data.

Habitat and distribution

Ecology. A saprotroph growing on dead wood of broadleaved trees: on trunks, stumps and branches. It occurs mainly on beech, but has also been recorded on birch, alder, hornbeam, poplar, oak, rowan and linden. It often grows together with the polypore known in Polish as "wrośniak szorstki" and, along with it, is among the first fungi to decompose dead wood. The fungus Dialonectria episphaeria, which forms red, spherical fruiting bodies, parasitises its fruiting bodies.

Distribution. Europe, North America, Asia and the islands of the Indian Ocean. Common in Poland. Not legally protected in Poland.

Fruiting. All year round.

What can it be confused with?

• Hypoxylon howeanum — Smoother surface, without distinct perithecial "mounds"; spores smaller. The anamorph is set on radiating strands of hyphae resembling white cobweb. Both species have the same chemotype and are sometimes intermixed, so reliable identification requires a microscope.
• Hypoxylon fuscum — Smaller stromata (up to 4 mm in diameter); grows on hazel and alder.
• Hypoxylon rutilum — Also grows on beech; distinguished microscopically by smaller spores.
• Species of the genera Annulohypoxylon, Nemania and Rosellinia — Similar carbonaceous stromata on dead wood; telling them apart requires microscopic and chemical features.

Never rely on a single feature. If you are not sure — do not pick it; show the mushroom to a qualified mushroom expert.

Interesting facts

• Persoon described this species in 1794 as Sphaeria fragiformis; its current genus name was given to it by Kickx in 1835.
• The epithet fragiforme means "strawberry-like" (Latin fragum); the stromata have a reddish surface covered with mounds.
• It is among the first fungi to start decomposing dead wood, often together with the polypore known in Polish as "wrośniak szorstki".
• Another fungus, Dialonectria episphaeria, parasitises its fruiting bodies, producing red, spherical fruiting bodies.