Thallus thin, sometimes effuse or conspicuous, smooth or ± rimose-cracked, white, grey, pale or deep brown, often with an olive tinge. Isidia and soredia absent. Photobiont Trentepohlia.
Anamorph: conidiomata pycnidia, black, often numerous, intermixed with the lirellae. Conidia of three types, sickle-shaped and 9-18 × 1-1.5 μm, or 9-14 (-17) × 1-1.5 (-1.8) μm, or bacilliform and 3-5 × 1-1.5 (-1.8) μm.
Teleomorph: ascomata lirellate apothecia, (0.5-) 0.8-2 (-3) × 0.15-0.25 mm, 50-100 µm high, very variable, sessile or semi-immersed, elongate, serpentine-sinuate, simple or often furcate, sometimes stellate or forming an interlinking network. Disc persisting as a slit, only rarely becoming partially exposed in older apothecia. Exciple K–. Epithecium dull chocolate-brown. Hymenium 45-60 μm tall, I+ red. Interascal tissue of pseudoparaphyses, septate, branched, often richly anastomosed, the apices not or rarely slightly swollen. Asci clavate-cylindrical, fissitunicate, with a minute K/I+ blue apical ring, 8-spored. Ascospores (15-) 20-30 (-40) × 2.5-4 (-4.5) μm, clavate to elongate-acicular, tapered at one end, straight or somewhat curved, 4- to 7- (to 8-)- septate, thin-walled, with a broad gelatinous sheath.
Chemistry: thallus C–, K–, KC–, Pd–, UV– (no lichen products detected by TLC).
Assessed by Woods & Coppins (2012) as of Least Concern.
This widespread and variable species is distinguished from Opegrapha niveoatra by the characteristic, longer, curved conidia. The saxicolous O. lithyrga is very similar.
Throughout the British Isles, except the English Midlands. BLS map here.
On shaded, smooth, young bark or smooth and rough areas of old trunks of a wide range of tree species; common.