What is the green stuff growing on the bark of my tree?
Lichens are associations of a fungus and an algae or bacterium that can produce food for the fungus. Usually the Lichens are green colored and growing on the bark of a tree, or sometimes surrounding rocks and soil. Lichens are not harmful to trees. It is sometimes said that Lichens always grow on the north side of a tree so that you might find your way if you were lost. There are more reliable methods to find your way.
