Usnea is a genus of mostly pale grayish-green fruticose lichens that grow like leafless mini-shrubs or tassels anchored on bark or twigs. The genus is in the family Parmeliaceae. It grows all over the world including here on Sibuya Game Reserve.
Members of the genus are commonly called old man’s beard, or beard lichen. It resembles Evernia, which is also called tree moss.
Like other lichens, Usnea often grows on sick or dying trees due to the pre-existing loss of canopy leaves, allowing for greater photosynthesis by the lichen’s algae; this leads some gardeners to mistakenly blame the lichen for the tree’s leaf loss and illness.
Usnea is very sensitive to air pollution, especially sulfur dioxide. Under bad conditions they may grow no larger than a few millimetres, if they survive at all. Where the air is unpolluted, they can grow to 10–20 cm long. It can sometimes be used as a bioindicator, because it tends to only grow in those regions where the air is clean, and of high quality.
According to Paul Bergner, Author of Medical Herbalism. “The usnic acid in usnea is effective against gram positive bacteria such as streptococcus and staphylococcus, making usnea a valuable addition to herbal formulas for sore throats and skin infections. It is also effective against a bacterium that commonly causes pneumonia.