A Spanish moss-like substance can be seen hanging from spruce trees around Summit County. There are a number of spruce trees in a cluster in Cucumber Gulch in Breckenridge, which has this growing on them. The trees themselves seem to be dead, as there are no needles on the branches.

The moss is actually a lichen called “Usnea,” which is the name of several species of lichen that grow hanging from tree branches, resembling greenish gray hair. It is commonly called Old Man's Beard, beard lichen or tree moss.

Did the lichen kill the trees, or do they prefer dead or dying trees? Because they do seem to prefer trees or shrubs already beginning to die, the lichen is often unjustly blamed for adversely affecting the tree. In actuality, many lichens grow rapidly when exposed to full sunlight, and that is why they are a common occurrence on dead or dying trees. Their position on the trees gives them a secure location to anchor as well as access to sunlight in dark forests. When the tree whose canopy is failing eventually dies, the lichen's growth greatly increases because of the additional sunlight. This is why many dead or dying trees are often covered with lichens. Dying trees also often release a kind of sugar or sap, a lure for lichen — but lichens do not consume any part of the plant, nor do they poison it.

Lichens are not parasites. They are actually two organisms living in a symbiotic relationship: a fungus and an alga; the original odd couple. Biologist love to use lichens as a perfect example of symbiosis: when two organisms live together and mutually benefit. The algae uses the sun to photosynthesize (produce food) while the fungus provides the support structure and water and mineral transport system. The body of most lichens is quite different from those of either the fungus or alga growing separately, and many resemble simple plants in form and growth. The fungus surrounds the algal cells, often enclosing them within complex fungal tissues which are unique to lichen/algae associations.

Lichens are capable of surviving extremely low levels of water. They gain water and mineral nutrients mainly from the air through rain and dust.

Lichens occur in some of the most extreme environments on Earth, like the arctic tundra, hot deserts and rocky coasts, but they are also abundant on leaves and branches in rain forests and temperate woodland.

Lichens can survive unprotected in space. In an experiment, two species of lichen were sealed in a capsule and launched on a Russian Soyuz rocket on 31 May 2005. Once in orbit, the capsules were opened and the lichens were exposed to the vacuum of space with its widely fluctuating temperatures and cosmic radiation. After 15 days, the lichens were brought back to Earth and were found to have no discernible damage from their time in orbit.

When growing on mineral surfaces like rocks, some lichens slowly decompose them by chemically degrading and disrupting the minerals. This contributes to the process of weathering by which rocks are gradually turned into soil.

The lichen Usnea grows on every continent. There are more than 600 recognized species. It has a white core that can be seen when it is pulled apart. The pale green “hairs” are a bit elastic and can grow to almost 12 inches long.

Usnea has been used medicinally for at least 1,000 years. Usnic acid, a potent antibiotic and antifungal agent, is found in most species. This, combined with the hair-like structure of the lichen, means Usnea lent itself well to treating surface wounds when sterile gauze and modern antibiotics were unavailable. It is also edible and high in vitamin C. Usnea also is reported to have anti-inflammatory properties.

In modern American herbal medicine, Usnea is primarily used in lung and upper respiratory tract infections, and urinary tract infections. Usnea also has shown usefulness in the treatment of fish infections in aquariums and ponds. There is no formal scientific information on the safety or efficacy of oral use of Usnea, although its long history of use strongly suggests there must be some merit in the claims. Search of herbal literature will yield many articles about the uses of Usnea.

Usnea's particularly efficient ability to absorb minerals from the air has made them useful indicators of air quality. Usnea are among the organisms most sensitive to airborne pollutants. Absorbed pollutants can upset the delicate balance of the lichen's symbiotic relationship enough to kill it.

Usnea — or Old Mans's Beard — are rich in nutrition. They are a food source for deer, which explains is why it's seldom found close to the ground. Deer will devour whatever they can reach. It is therefore most easily spotted on branches at least 6 feet above ground, just out of reach of whitetails. As soon as lichen-covered branches break or a tree falls, deer consume every “beard” within reach. Lichens are also used by the Northern Flying Squirrel for nesting, food, and a water source during winter. Usnea has also been found in the nesting material of 50 species of birds.

If you are lost in the woods without supplies, the absorptive qualities of Usnea make it useful as wound dressings, baby diapers and feminine sanitary absorbents.

Breckenridge resident Dr. Joanne Stolen is retired from teaching microbiology at Rutgers University.