Description: This eye-catching epiphyte is usually sterile (the brown-black discs are rare), yet even in this state it has a distinctive appearance owing to the blue-green granular-isidiate thallus seen growing between and among tree bark mosses. It occurs in coastal woodlands of oceanic areas especially on oak. In Ireland, it occurs mostly in the west where it is local.

Key Identification Features:

• Thallus blue-green, granular; sometimes just a smear, yet it has a strange prismatic glow when overgrowing bark mosses
• On oaks in old established oceanic woodlands.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Bacidia caesiovirens at iNaturalist World Species Observations database.