Lichen

Lichen (pronounced “liken”) is a biological class of complex organisms (a fungus and alga or cyanobacterium) that have a symbiotic relationship. The green algae and cyanobacteria produce food by photosynthesis. The fungi cannot photosynthesize, but provide a protective exterior surface for the algae/cyanobacteria. This enables the algae/cyanobacteria to exist in full sun, thus maximizing its ability to produce food for both. Lichen gain water and mineral nutrients mainly from the atmosphere, through rain and dust. THis is not a disease and will not hurt the tree or shrub.

Lichen not only grow on plants but on the ground and on rocks. Lichens have a great deal of variability in color and form depending on the species. The color can range from white to green to yellow/orange/red, and some have black specks. Some are flat and others look like ruffles. Some look like small, leafless shrubs.