Lichen it to Some Other Problem By Jerry A. Chenault, Urban Regional Extension Agent, Lauderdale County

Lichens are inconspicuous, hardy, and adaptive plants that are composed of fungi and blue-green algae. This union produces an organism unlike the fungi or algae. Both partners contribute to its growth and survival. Most of the lichens you see on trees are probably gray-green; however they vary in color from yellow and orange to dark brown.

The appearance of lichen is usually related to damage from environmental stress or poor management. Exposed limbs on damaged plants simply give lichens access to the sun they need for growth with little competition.

Lichens are not picky about where they live. They can be found on exposed surfaces of limbs, stumps, fence posts, soil, rocks, and other living and nonliving objects. They attach firmly to their host and are usually found on limbs and trunks of large mature trees and shrubs in full sun. Lichen is most commonly found on trees with thin canopies. They usually do not thrive on heavily shaded twigs or branches of healthy woody plants.

Lichens reproduce by pieces breaking off and fragments being spread by wind, splashing water, or other means. Generally, their reproduction process is not a concern. However, certain kinds of lichens on leaves may shade foliage, and thick coverage on limbs may interfere with gas exchanges of plant tissues.

Good plant vigor is the best defense against lichens. Good growing conditions, proper watering, and soil fertility are major parts of this defense. Light pruning of affected limbs will remove some lichens and stimulate new shoot growth to help shade out other lichens. There are no pesticides registered for the control of this plant life.

Unfortunately, lichens often get blamed for killing trees or shrubs. So, if lichens are innocent bystanders, then who killed your tree? A good possibility is your lawn mower or weed trimmer. These machines cut through the bark, girdle trees, or just knock the bark off causing damage or complete desolation of the plants water-carrying vessels inside. Other problems could be caused by borer insects, the lack of fertilizer, or several other arboreal criminals. It's not likely that the "lichen brothers" were involved at all. Therefore, I enter a plea of innocent on their behalf and ask that we clear their name once and for all. All of this false blame could be "lichened to slander."

Reeves, C. (1999, January). Lichens on trees. Yard & Garden Brief. University of Minnesota Extension. Retrieved July 23, 2009.

Shigo, A. L. (2003). Modern arboriculture: Touch trees. New Hampshire: Sherwin Dodge Printers.

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