Description: This unmistakable, mustard-yellow ‘powder lichen’ of shaded, hard limestone underhangs and crevices can be told by its colour, lobe-like margins and spot tests. It can form thalli many centimetres wide or smaller fragments of a few millimetres or so where it is starting to become established. A white medulla may be seen where the surface is broken. Reactions: K+ purple. Northern half of Ireland, much rarer in the south.

Key Identification Features:

• Thallus mustard yellow, of powdery granules above a white medulla
• Edges clearly lobed; K+ purple, on hard, shaded limestone.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Leproplaca xantholyta at iNaturalist World Species Observations database.