Posted December 28, 2022
If you look up into the branches of the oak trees around us, you may notice some branches coated in a greenish fuzz. This fluffy stuff is a lichen. Lichens come in various shapes and colors, but the one commonly seen in our area, is Usnea, or Old Man’s Beard. If you don’t see any in your neighborhood, look for it on some of our trails.
Lichen are two (or more) organisms existing in a symbiotic, or mutually beneficial, relationship. Usnea consists of an alga which provides food through photosynthesis and a fungus which prevents the lichen from drying out through its network of protective filaments. As a result, lichens can often survive extended dry conditions.
Old Man’s Beard can be seen at the bare tops of trees and on bare branches, but it is not harming or killing the tree! After something else has damaged the tree (such as harsh weather conditions or gypsy moths), the lichen settles on the dead or dying branches. The absence of leaves allows for greater photosynthesis for the algae. The lichen flourishes where there is no leafy canopy blocking the sun.
Usnea is sensitive to air pollution and will not grow or thrive unless there is good air quality. So, all that fuzz in the trees around us is doing no harm to us or the trees, and it’s letting us know what nice clean air we have!
Written by Dee Jepson, Board Advisor