A foliose species with a straplike, shiny, chestnut to dark brown thallus that is frequently more red towards the base. Its relatively large lobes form dense tufts or entangled mats. The lobes are long and curl inwards, and ciliate on the margins. Marginal pycnidia are common.
Medulla: C-, K-, UV-
In Scotland, Cetraria islandica has a more restricted upland distribution where it is common on lichen-rich heath. BLS distribution map
Cetraria islandica is distinguished from Cetraria aculeata on basis of its broader lobes that curl inwards and appear channeled.
scottishlichens.co.uk 