Large -bodied foliose lichen which is pale green, green-yellow to green-grey in colour. It turns grey in shaded areas. It has a rough, corrugated appearance. It has conspicuous course soralia (structure bearing powdery reproductive cells), which mainly inhabits the centre of the thallus (body of the lichen). Apothecia are rare. Thallus 5 to 20cm in diameter.
Found on many substrates, including broadleaved trees, silca-rich rocks, town monuments, fences and roofs. A common and widespread species, although scarcer in central and northern Scotland.