Description: Do not expect to find this lichen on limestone. It is a species of upland siliceous rock; it is common and widespread but easily mistaken for a host of lookalikes. It is usual for the thallus to be greenish or grey but it can also be reddish, especially near water where it can become oxidised. Discs are numerous, black, relatively large, occasionally convex with the margin smooth and to 0.2mm diam. They are very rarely frosted as in related species. Look for it on screes, tumbledown boulders and dry stone walls by upland streams.

Key Identification Features:

• Acid-rock lichen bearing large black discs reaching 3mm diam.
• Discs rarely frosted with their black margins smooth to 0.2mm diam.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Porpidia macrocarpa at iNaturalist World Species Observations database.