Lichen on bark

Lichens are composite organisms consisting of two organisms in a symbiotic relationship.  Lichens are composed of a fungus  with a photosynthetic partner, usually either a green alga or a cyanobacterium.  Lichen appearance can differ greatly.  Lichen can not only appear as smooth patches on the bark of your tree or shrub but also they can appear small shrubby growths.

The important thing to remember is that lichens do not harm trees or shrubs.

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