Lichen on trees is generally not harmful. Lichens are unique organisms made up of a symbiotic relationship between fungi and algae. They grow on the bark of trees, rocks, and other surfaces but do not feed on the tree itself. Unlike parasites, lichens do not harm the tree because they do not extract any nutrients from it.
In fact, the presence of lichen is often a sign of good air quality, as lichens thrive in areas with clean air. However, if a tree is declining and you notice more lichen, it’s not the lichen that’s causing the damage—it could be other issues like pests, diseases, or environmental stressors. The lichen is simply growing on the surface and may be more visible as the tree weakens.
