Skip to main content

U.S. Forest Service

Plant of the Week

USDA Plants distribution map for the species. No range map available for Usnea longissima. USDA PLANTS Database.

Usnea longissima, old man’s beard. Usnea longissima, old man’s beard. This rare lichen hangs from a central stalk and can get up to several feet in length. Its habitat is shrinking and instead of establishing itself via spores, parts of it break off and reestablish elsewhere. It is a strong indicator species of air pollution. Photo by Karen Dillman, U.S. Forest Service.

Bearded Lichen (Usnea longissima Ach.)

By Chantelle DeLay

Also known as Methuselah’s beard and old man’s beard, Usnea longissima is a lichen in the family Parmeliaceae (Kingdom Fungi). Usnea longissima is found in Western Europe and North America. In North America, it is found along the Pacific Coast from northern California to southern Alaska. It has also been found in the Upper Midwest and north of the United States and Canada border along the Great Lakes and east to the Atlantic Coast. Although it has a large range and was once common, Usnea longissima is now considered rare in the United States. Reasons for its rarity include pollution and loss of habitat.

This species is a pendant lichen that hangs from tree branches. It is a light yellow-green lichen with a central cord and short branches coming off of the central cord. In all Usnea species, the central cord is like an elastic band surrounded by a hard fungal cortex. Usnea longissima can be from 6 inches long up to 20 feet long. Specimens in the Pacific Northwest tend to be longer and bigger than their eastern counterparts. This species main method of reproducing is through fragmentation. Parts of the lichen body break off and colonize elsewhere, developing a new lichen structure. Very few Usnea longissima lichens have been seen with spore-producing structures and are considered very rare.

Usnea longissima is normally found in open or shaded forests that are near bodies of water such as lakes or rivers. It grows in the crowns of coniferous trees. Most of the research in the United States has been focused on the populations in the Pacific Northwest since that area seems to be where the largest populations are found, as well as where the largest population of lichen researchers is found. They generally find this species in old growth Douglas fir forests but it has also been found in younger forests in different trees. One of the main research goals for this species is its response to air pollution. Usnea longissima is extremely sensitive to air pollution and has died out from most of its range. Air pollution affects many lichens, overwhelming their bodies with toxic chemicals, blocking their normal metabolic functions. See the National Lichens & Air Quality Database and Clearinghouse.

Human uses for this lichen include bedding, medicine and straining pitch for canoe sealant. Animals use this species and other species of Usnea for forage and nesting material.

For More Information