Description: This large foliose lichen is like an extravagant version of P. perlatum but with broader, incised lobes, inrolled edges with only little soredia to show for it, and very few marginal cilia. The medulla tests Pd+ deep orange to rust red, not Pd+ yellow to orange as in P. perlatum. Restricted to south-west Ireland, where it is rare. The species has not been seen recently.

Key Identification Features:

• Like P. perlatum but has broader lobes, fewer soralia on the lobe tips, inrolled lobe edges and very few marginal cilia; medulla is Pd+ deep orange, never yellow
• Exposed coastal scrub and mossy rocks.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Parmotrema robustum at iNaturalist World Species Observations database.