Oakmoss on apple trees in the orchard at Aydon Castle, Northumberland
Evernia prunastri, also known as oakmoss, is a species of lichen. It can be found in many mountainous temperate forests throughout the Northern Hemisphere. Oakmoss grows primarily on the trunk and branches of oak trees, but is also commonly found on the bark of other deciduous trees and conifers such as fir and pine. The thalli of oakmoss are short (3–4 cm in length) and bushy, and grow together on bark to form large clumps. Oakmoss thallus is flat and strap-like. They are also highly branched, resembling the form of antlers. The colour of oakmoss ranges from green to a greenish-white when dry, and dark olive-green to yellow-green when wet. The texture of the thalli is rough when dry and rubbery when wet. It is used extensively in modern perfumery.