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(Map updated: 11 August 2009)

This powdery, crustose, epiphytic lichen is a recent addition to the Irish lichen flora. It is a species of the waysides, so is absent from woods. The pale grey thallus is finely cracked and tinged with yellow which gives it a distinctly lime green appearance and useful field character. The yellowing is a flush of powdery soredia which spreads thinly across the surface. The edges of the thallus are place to see the white prothallus growing out from below the crust. Discs are rare. Spot tests: K+ yellow-red, C-, PD+ yellow.

Key characteristics

• Thallus crustose, cracked, grey to lime green; wayside trees
• Soredia fine, powdery, yellow-green; K+ yellow-red, C- (NOTE: both Lecanora expallens and Pyrrhospora quernea are C+ orange).

Original text submitted by Vince J. Giavarini