Corticolous; on deciduous trees (sometimes saxicolous); very common.

Upper surface glaucous grey, with an coarse white reticulum, developping to green-grey soralia (mainly in the center of the thallus); lobe ends brownish; lower surface black, with numerous rhizines; medulla and soralia K+ orange-red, P+ orange.
Distincted from P. saxatlis by the lack of isidia and from P. omphalodes by the grey colour (the latter is brown).

Central Europe. Austria: Alps. Portugal: Madeira.    Sweden.