A crustose species with an often white-grey, thin thallus. The orange apothecia often have a distinctively flexuose margin.
Thallus: K-; apothecia: K+ purple
In Scotland, Caloplaca ferruginea is found mainly in the Highlands where it grows on twigs of trees with neutral to base-rich bark, including hazel, aspen, ash and bird cherry. BLS distribution map
scottishlichens.co.uk 