Rock tripe

Rock tripe is the common name for various lichens of the genus Umbilicaria that grow on rocks. They can be found throughout northern parts of North America such as New England and the Rocky Mountains. They are edible when properly prepared and have been used as a famine food in extreme cases when other food sources were unavailable, as by early American northern explorers.

Umbilicaria esculenta is commonly used as a food in Asian cuisine and a restorative medicine in traditional Chinese medicine. It is called shi'er (石耳 "rock ear") in Chinese cuisine, iwatake (岩茸 "rock mushroom") in Japanese cuisine, and seogi (석이버섯) in Korean cuisine.