Lecanora loekoesii grows as a thin, grey crust on tree bark. The lichenised "body" (
thallus) hugs the surface so tightly that it looks painted on (a
growth form called
crustose). It is continuous rather than patchy and can feel smooth or slightly rough; there is no powdery coating () on the surface and no production of
sorediate granules for vegetative reproduction. A distinct dark boundary () is absent. The
fruit bodies (
apothecia) are abundant and sit directly on the crust, each 0.4–1 mm across. They have a construction typical of
Lecanora: a fleshy rim made of thallus tissue (a ) surrounding a . The margin is usually whitish-grey and thinner than the surrounding crust, while the disc is yellow-brown and may carry a light dusting of white pruina. Microscopic sections show that the rim contains many minute, K-soluble crystals and lacks a proper outer . The upper part of the spore-bearing layer () is golden brown and studded with fine granules that also dissolve in potassium hydroxide (K). The "fine granules" were later interpreted as "coarse granules" by Chinese lichenologists after studying Chinese specimens. Beneath this, the clear
hymenium is about 65 μm tall, sitting on a colourless and . Inside each club-shaped
ascus are 12–16 colourless, single-celled
ascospores. These spores are
ellipsoid, measuring roughly 13–15 μm long by 7.5–8.5 μm wide, with very thin walls (< 0.7 μm). No flask-shaped
pycnidia (structures that make asexual spores) have been observed in the species. Standard chemical
spot tests on the thallus yield K+ (yellow), KC+ (yellow), and P+ (yellow) reactions, matching the presence of the secondary metabolites
atranorin,
usnic acid,
zeorin, and
norstictic acid. In 2017, the species
Lecanora subloekoesii was described from specimens collected from
Heilongjiang, China; it differs from its namesake
L. loekoesii in the brown to reddish-brown colour of its apothecial discs, and its eight-spored asci. ==Habitat and distribution==