Ah, I found it.
http://www.clemson.edu/extensi...
" Lichens: A lichen is an unusual organism composed of a fungus and an alga living together in the same body. Lichens often appear as green to gray-green leafy or crusty growths on the trunks or branches of plants. Typically, they occur in abundance on plants that are declining in health or vigor. They are harmless to the plant, and are in no way responsible for the poor health of the plant. Less vigorous plants tend to be more open, increasing sunlight penetration, and subsequent lichen growth."
These trees are right out in the open, away from everything else. Strange.
