Description: With time, it becomes possible to distinguish this lichen among the other crusts growing on old, mature trees in acid woodland, though it is perhaps best, at first, to have an experienced lichenologist point it out. The major distinguishing features are (i) the colour of the thallus, which is pale, blue-green (when fresh), and (ii) the small, finger-like scales (squamules), shaped like the pseudopodium of an amoeboid protozoan, covered in tiny soft hairs (pubescent). It is occasional on oak in damp woodlands where it can rapidly spread to mosses from crevices in the bark. In Ireland, the species is thinly scattered.

Key Identification Features:

• Thallus pale, blue-green to grey made up of short finger-like squamules covered with a soft down of crystalline hairs
• It most commonly grows in damp ancient woodlands on rough-barked trees such as oak, where it can quickly spread to mat-forming mosses.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Phyllopsora rosei at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Phyllopsora rosei at iNaturalist World Species Observations database.