Cobb County Extension Service

FACT SHEET

LICHEN

email: uge1067@uga.edu

Have you seen these diseases before?

 Haematomma accolens

Are they on your shrubs or trees?

 Xanthoparmelia cumberlandia

Lichen

Lichens are the symbiosis between a fungus and an alga. Some fungi may be in association with more than one species of algae. Symbiosis is the interaction between two or more species that benefits at least one of them. With lichens it is thought that both the fungus and the alga benefit. The alga, under optimal conditions, produces simple sugars from atmospheric carbon dioxide and water by photosynthesis. The fungus provides shelter and protection for the alga. The alga's sugar production supplies both fungus and alga with nourishment. It does not destroy trees on which it is found growing; but may be a indicator of a stressed or weakened plant. They are not diseases. Haematomma accolens above is growing on the bark of a tree, while Xanthoparmelia cumberlandia is growing on a stone.

Lichens are able to grow in extreme environments; found in the hottest desert, the coldest tundra, and the wettest rain forest. They may grow on soil, debris, rocks, tree bark or leaves. There are more than 3600 species in the United States and Canada. Lichens are extremely vulnerable to habitat alteration and pollution. As such, scientists use them as indicators of ecosystem continuity and pollution damage. Most lichens grow very slowly, often less than a millimeter per year. They are able to shut down ("hibernate") during extended periods of unfavorable conditions and survive extremes of heat, cold, and drought.

With the right amounts of light, moisture, clean air, and freedom from competition, lichens can colonize almost any undisturbed surface. They have even been found growing on old auto tail-light lenses. Lichens provide refuge for spiders, mites, lice and other insects. Many cultures use lichens in many varied ways; some eat lichens (beware a few are poisonous), cloth has been dyed with lichens, drug companies make antibiotics from lichen substances.

Fun with Lichens, Oregon State University, http://mgd.nacse.org/hyperSQL/lichenland/

North American Lichen Project, http://www.lichen.com/

Lichen Research, Department of Botany, national Museum of Natural History, Smithsonian Institution, http://www.nmnh.si.edu/botany/projects/lichens/

Article written by former horticulturist Jack Arnott

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability.