In their natural habitat, lichens are a beautiful part of the landscape. But when they invade trees and shrubbery, homeowners frequently become concerned about their affect on the health of these plants. In most instances there is no real reason for concern, since lichens don't directly cause injury to landscape plants.
Lichens are unique creatures in the plant world.
However, the appearance is that of a single plant. Lichens manufacture their own food and grow on soil, on rocks, and trunks and branches of trees and shrubs. They occur in several forms such as crusty gray, green, yellow, or white growths. Some are leaf-like, others resemble a tuft of horse hair hanging from branches. Lichens are amazing creatures for other reasons as well.