What are those fuzzy and/or blotchy greenish/grayish patches on the trunks of my trees? Do they hurt the tree?
A. They are lichens, a combination of algae and fungi. The non-green fungi provide the structure and soaks up moisture. The green algae make food through photosynthesis. Lichens flourish in areas of high humidity like Cape Cod. They just sit on the bark of the tree. They don’t penetrate or hurt the tree. They’re usually on the north side, where the sun doesn’t dry out the plant as much.
