Bitter Wart Lichen

Bitter Wart Lichen is a common, widespread, fluff-wart lichen. It occurs in Europe, North America, and Central America. In the United States it occurs east of the Great Plains and on the West Coast.

Bitter Wart Lichen grows on the bark of both deciduous and coniferous trees. It occasionally grows in shady places on sedimentary rocks that are high in silicon (siliceous).

The vegetative body (thallus) is thin with moderately thick, wart-like bumps. The base is whitish gray to greenish gray and thin. It is tightly adhered to the surface (crusticose), appearing spray-painted on. The upper surface is coarse and covered with tiny dull granules (soredia). The outer margins are sometimes weakly zoned. The bumps are wart-like. This is the feature that gives the genus its common name. They stand out from the surface like a rash.

Cup-shaped reproductive structures (apothecia) are produced but they are not seen. They are buried in the thallus warts.

Tasting a small piece of the thallus will produce a very bitter flavor in the back of the mouth that will last a long time. Though unpleasant, it is not poisonous, and it is a sure way to distinguish this species from Pore Lichen (Lepra albescens). The taste test should not be necessary though, because Pore Lichen is very rare in North America.

Trees

Crusticose

Deciduous and coniferous trees

Sources

4, 24, 26, 29, 30, 77, 81.

Common and widespread

lichens on red oak

Location: Cass County

lichens on red oak