Pertusaria amara

Pertusaria amara

Common Names

Bitter wart lichen (English)

Languages: English



Bitter wart lichen (Pertusaria amara) is a crustose lichen often found on rock. It is also known as Pore lichen, along with other members of its genus. It is gray and grows in a hard, circular structure close to the rock.


Look Alikes

Other members of the genus Pertusaria are called pore lichen, although none share the name bitter wart lichen.


Bitter wart lichen is a crustose lichen, meaning that is is flat and hard and very difficult to detach from the underlying surface without pulling up some of the surface with it. It forms circular colonies in which individuals are represented by tiny bumps. It is light gray and smooth to the touch.

Ecology and Distribution


Pertusaria amara is found across eastern North America.


Bitter wart lichen is often found growing on rock, although it also grows on other surfaces such as bark and fallen material.

Trophic Strategy

Lichens are a symbiosis between a fungus and a green alga or sometimes a bluegreen alga (cyanobacteria). They algae engages in photosynthesis while the fungus chemically and physically decomposes the rock or other surface to obtain needed nutrients.



Due to its bitter taste, pertusaria amara was thought to reduce fever (because other naturally occuring fever reducers are bitter) and eaten to this purpose. However, its efficacy has not been proved. It is not poisonous.