Old Man's Beard

Usnea is a genus of mostly pale grayish-green fruticose lichens that grow like leafless mini-shrubs or tassels anchored on bark or twigs.[1]:203 The genus is in the family Parmeliaceae. It grows all over the world.

Members of the genus are commonly called old man's beard, or beard lichen.[1]:203 It resembles Evernia, which is also called tree moss.[2]

Like other lichens it is a symbiosis of a fungus and an alga. In Usnea, the fungus belongs to the division Ascomycota, while the alga is a member of the division Chlorophyta.

Members of the genus are similar to those of the genus Alectoria.[1]:148 A distinguishing test is that the branches of Usnea are somewhat elastic, but the branches of Alectoria snap cleanly off.[1]:148