Description: This crustose lichen has a thin to thick, grey coloured thallus scattered with white, finely-granular soredia which stands out from the surface like a white rash. This is the only lichen for which taste can be used as a means of certain identification. Wet a finger against the soredia and dab on the tongue; then wait a second or two. The bitter taste is oxalic acid. The absence of a bitter taste suggests you may have encountered a lookalike species, P. albescens. Even the most experienced lichenologists trust the taste test. Beginners trying it out for the first time soon learn that only a few grains of soredia is all that is required to achieve a successful outcome. Common: acid-barked trees such as oak and beech, rarer on rock.

Key Identification Features:

• Scattered white soredia on a grey thallus
• Taste-test for oxalic acid — a must, for certain identification.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Lepra amara at iNaturalist World Species Observations database.