Description: This attractive species, which is very similar to the leafy Parmelia taxa, may be known at once by its large, grey thallus (to 10cm wide) and presence of white dots (technically named pseudocyphellae) across the surface of the lobes. In well-grown specimens the edges of the lobes produce powdery soredia. The underside is black towards the centre with a pale brown, shiny margin; lobe tips lack the marginal hairs (cilia) of Parmotrema perlatum (described elsewhere). Well-illuminated acid-barked trees (for example, hazel and sallow) in damp, mossy woodlands; often by rivers or loughs. Local. Throughout Ireland.

Key Identification Features:

• Large grey, leafy thallus, the wavy lobes sorediate at the edges and dotted with numerous pseudocyphellae
• Underside is black with a pale, shiny margin. Platismatia glauca has its lobes crisped and is isidiate but lacks dots on the lobes and has a less widely spreading thallus.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Cetrelia olivetorum s. lat. at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Cetrelia olivetorum s. lat. at iNaturalist World Species Observations database.