University of Maryland Extension

Featured Plants - Lichen

Lichen spp.

All right, technically lichen is not a plant.  It is algae cells enclosed in fungal cells, working together in a symbiotic relationship.  Lichen (the word is singular and plural) draws water and nutrients out of air.  That’s how it can live on inhospitable surfaces such as a rock or fence or tree trunk.  Although it attaches, it has not roots so surfaces are not harmed. A common tree lichen in Maryland is greenish gray and crusty, but combinations of different algae and fungi have evolved into many lichen colors and forms. Their main enemy is air pollution, because they are dependent on air for sustenance.  Lichen on a tree, it is not cause for alarm. A tree covered in lichen, however, may signal other problems.    
(February 2013)

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