Anamorph: Virgariella-like. Conidiomata absent, colonies bright yellow-orange, velvety, forming on young stromata. Conidiophores not well differeniated. Conidiogenous cells 16-47 x 2-4.8 µm, yellowish to rusty, finely to coarsely roughened, proliferating sympodially with well-defined rhexolytic secession. Conidia 3.5-5.5 x 2.8-3.5 µm, ellipsoidal to citriform, hyaline, aseptate, thin- and smooth-walled. Chlamydospores 4-6 µm diam, globose to ellipsoidal, coarsely encrusted, rusty, originating from conidiophores and from vegetative hyphae.
Teleomorph: stromata 6-35 mm diam x 1-1.6 mm thick, discoid to effused-pulvinate, frequently coalescent, with inconspicuous or infrequently conspicuous perithecial mounds, surface sienna or rust-coloured, powdery when young with a villose, ochreous to sienna margin, becoming dark brick-red to sepia when mature, with orange granules beneath the surface and between perithecia, with orange to sienna KOH-extractable pigments. Stromatal tissue below the perithecial layer blackish brown to black, 0.5-1.2 mm thick. Ascomata perithecia, 200-300 µm diam. x 400-580 µm high, obovoid to tubular. Ostioles lower than or at the same level as the stromatal surface, at the centre of a black discoid area 40-80 µm diam. Asci 145-170 x 6-7.5 µm, the spore-bearing parts 60-77 µm long, the stipes 80-96 µm long, the apical ring discoid, amyloid, 1-1.2 µm high x 2-2.8 µm broad. Ascospores 8-11.5 x 4-5.5 µm, brown, ellipsoidal, nearly equilateral, smooth-walled, with a straight spore-length germ slit, with a perispore that is indehiscent in 10% KOH.
Not formally assessed, and perhaps under-recorded due to confusion with other members of the Hypoxylon rubiginosum complex.
The broght yellow-orange velvety anamorph is distinctive.
On rotten wood of various angiosperm trees, frequently encountered on Salix.
Widely distributed in southern England, also in Northern Ireland.