Description: This crustose twig and branch bark epiphyte has a brittle Pd + red, green-coloured thallus with small areoles and bright green, farinose soralia. The discs are grey-brown and thinly frosted; spores one-septate. Its habitat appears to be spreading horizontal branches and twigs, especially oak. It is known from Counties Cork, Waterford, Fermanagh and Donegal.

Key Identification Features:

• Brittle (disintegrating when touched with a needle), pale to olive green thallus with farinose soredia; Pd+ red; discs pale grey to brown, spores with thick perispore
• On acid-barked tree branches; Rinodina efflorescens is similar, has larger areoles and is also Pd + red, but is not brittle when touched with a needle; it is always without discs.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Halecania viridescens at iNaturalist World Species Observations database.