Thallus very variable; rather smooth, even and continuous or granular-verrucose, almost white or yellow-grey to yellow-green in sunny, exposed sites, becoming grey-green in shade, rarely almost absent, at times forming mosaics. Prothallus black or blue-black, sometimes very prominent. Soralia and isidia not present.
Anamorph: conidiomata rarely seen, pycnidia, immersed in the thallus with the black ostiolar region slightly protruding. Conidiophores not clearly developed, the conidiogenous cells developing in a palisade from the inner surface of the conidioma wall; rather irregular in shape, broadly cylindrical, tapering or doliiform, probably proliferating percurrently but with collarette absent and periclinal thickening not obvious. Conidia 12-15 x ca 1 µm, filiform, strongly curved, aseptate, hyaline, thin-walled, smooth.
Teleomorph: ascomata apothecia, to ca 1 mm diam., closely appressed, rounded to irregular, at first plane, later convex; occasionally in clusters on a common melanized base. Disc black in exposed, well-lit situations, sometimes pale blue-black, brown-red, cream-yellow or ± piebald with a darker true exciple (the variation possibly associated with shade). True exciple persistent, flexuose, finally excluded, concolorous with the disc. Epithecium and edge of true exciple blue-green to dull grey-blue [visible in sections], with crystals that dissolve in K. Hymenium 40-70 μm tall, sometimes with crystalline inclusions in the lower part and in the hypothecium. Hypothecium brown-orange, rarely colourless, intensifying to bright red-brown in K. Interascal tissue of rather broad and thick-walled unbranched non-capitate paraphyses. Asci cylindric-clavate, thick-walled, short-stalked, with a very large apical cushion staining dark blue in Lugol's iodine, with an inner non-staining column that does not reach the apex, similar to that seen in Bacidia species; 8-spored. Ascospores arranged biseriately, 10-17 × 6-9 μm, ellipsoidal to ovoid-ellipsoidal, fairly thick-walled, hyaline, without a gelatinous sheath or epispore.
Chemistry: thallus C+ orange, K+ yellow, KC+ yellow, Pd– (reactions often faint, arthothelin, granulosin, ± 4,5 dichlorolichexanthone).
Assessed by Woods & Coppins (2012) as of Least Concern; this is one of the commonest crustose corticolous lichens in GB&I.
The species can be distinguished by the lax, simple paraphyses, the blue-green epithecial layer and a red-brown hypothecium intensifying in K, and at least a part of the thallus reacting C+ orange.
Lecidella elaeochroma forma soralifera has bright yellow-green punctiform soralia but is otherwise similar. Buellia disciformis is often confused with morphs of Lecidella elaeochroma with a pale thallus. Megalaria grossa can appear like a large form of L. elaeochroma but is C–. The rare M. laureri can also superficially resemble some morphs of L. elaeochroma.The mainly continental and Asian L. euphorea, distinguished by the thallus reactions C–, K+ yellow (?atranorin), is poorly understood and is probably not correctly recorded from the British Isles.
Throughout the British Isles and Ireland. BLS map: here.
On well-lit smooth bark, especially twigs and small branches, also on worked timber. Often forming mosaics, moderately tolerant of SO2 air pollution.