Thallus effuse and granular to rimose, usually forming circular to elongate patches, yellow-green, sometimes with radially orientated crystals evident on the surface. Soredia initially arising from discrete, somewhat excavate, lens-shaped soralia 100-300 µm in size, soon becoming confluent to make a continuous sorediate crust, farinose, pale- to lemon yellow. Prothallus inconspicuous or when on smooth bark blue-grey.
Anamorph: no information available.
Teleomorph: ascomata apothecia, frequently absent, 0.3-0.8 (-1.5) mm diam., sessile, not constricted below, sometimes angular by compression. Thalline exciple at first crenulate but becoming excluded, sometimes sorediate. Disc pale yellow, pink or brown, flat to slightly convex, sometimes pruinose. Epithecium hyaline to pale yellow. Hymenium 35-55 μm tall. Interascal tissue of paraphyses 1.5-2 μm diam., sparsely branched and anastomosed, apices not or slightly thickened. Ascospores 10-16 (-17) × 4-7 (-7.5) μm, broadly ellipsoidal.
Chemistry: thallus C+ deep yellow or orange to red, K+ yellow, Pd–, UV+ orange (thiophanic and usnic acids, ± arthothelin and ‘expallens unknown’).
Assessed by Woods & Coppins (2012) as of Least Concern.
A member of the Lecanora polytropa group. When sterile, this species may be confused with Pyrrhospora quernea, which has a somewhat duller, yellow rather than a yellow-green or citrine, thallus and coarser, nearly isidioid soredia; it also contains arthothelin and not usnic acid.
Common throughout the British Isles. BLS map here.
On bark, wood and worked timber, generally in well-lit or xeric situations, occasionally also on dry siliceous rock faces and vertical memorials or walls.