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Lichens and trees

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Lichen on a tree trunk
Photo: Jardin botanique de Montréal (Pascale Maynard)

Green trunks clean the air!

Why do some trees in a forest have greenish bark?

If you see something green growing on a tree trunk, it’s most probably lichens or mosses.

Mosses are non-vascular plants. Lichens, on the other hand, are composite organisms consisting of a symbiotic relationship between an alga and a fungus. Lichens are epiphytic, which means that they merely use trees as a place to grow. Their colors vary form gray to green, orange or even black.

Lichens offer a clue to air quality. Because they are intolerant of pollution, lichens do not often grow on city trees.

Lichens or mosses growing on a tree trunk do not mean that the tree is diseased and do not damage it in any way.

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