Orange Rock Hair

Trentepohlia aurea, the orange rock hair, is a species of filamentous terrestrial green alga in the family Trentepohliaceae. It grows on a variety of substrates including rocks, old walls, concrete surfaces, tree bark, rotting wood, mosses, and wet soil. The orange coloration results from carotenoid pigments in the algal cells.

Trentepohlia aurea is the type species of the genus Trentepohlia. In the British Isles, it is the most widespread and abundant species of Trentepohlia. However, many records need to be reassessed, since the name has been broadly misapplied to specimens of other species, such as Trentepohlia abietina.