Q.
A
number of trees in our backyard and the oak tree in our front yard
have pale green splotches all over their trunks. Can you tell me
what this is? Is it dangerous to the tree, and what can be done
about it?
A. From your
description and photos, the “problem” is lichens growing on the bark
of your trees. Lichens are a fungus living in a symbiotic (mutually
beneficial) relationship with blue-green bacteria. The fungus
surrounds the bacteria. They often grow on tree trunks, unfinished
wooden fences, and even rocks.
Lichens growing on a tree trunk
Lichens pose no threat to your trees' health, or to you and your
family. Their presence is actually a sign that the air in your
neighborhood is relatively clean - they do not grow in areas where
the air polluted. There is no reason to remove them, and you could
damage the trees' bark in the process.
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