Description: This lichen often grows on well-lit, siliceous boulders or low outcrops. When carrying out chemical testing using Potassium hydroxide (K) the beginner will find that these crusts suddenly turn blood-red. The rather thin, grey to grey-green thallus has a cracked surface with scattered isidia forming small mounds or they may become more dispersed and granular (soredia-like). Discs are black and are not uncommon. It tests K+ red and Pd + orange.

Key Identification Features:

• Grey to grey-green crust on siliceous rock; K + blood-red, Pd + orange
• The cracked thallus has scattered clumps of granular isidia.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Aspicilia grisea at iNaturalist World Species Observations database.