A conspicuous leafy lichen occurring on broad-leaved trees, heather and other lower growths. Bright to olive green with distinctly ridged surface often with soredia or isidia developing along the ridges. Still common in the north-west but sensitive to changing habitats

References: 
Smith, C.W. et al. editors (2009) The Lichens of Great Britain and Irelandd
Dobson, F.S. (2018) Lichens: an Illustrated Guide to the British and Irish Species
Ahti et al. editors (2012) Nordic Lichen Flora, Volume 3: Cyanolichens