https://creativecommons.org/publicdomain/zero/1.0/https://www.rawpixel.com/image/4024058
Lichen on tree.
Algae, lichens and moss are non-parasitic plant-like organisms that colonise bark, rock and other hard surfaces. Lichens and algae are often mistaken for a fungal disease but, fortunately, they do not harm plants on which they grow. Furthermore, they can give a mature look to a garden, preferring damp areas with minimal air movement. Original public domain image from Flickr
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