Rock Tripe

Rock tripe (Umbilicaria mammulata) is an edible lichen. There are 65 species of rock tripe, found in rocky or mountainous environments worldwide, especially where other organisms are scarce. The common rock tripe grows on shaded rocks in the forests of eastern North America.

Lichens are complex life forms that comprise at least two separate organisms, primarily a fungus and a photosynthesizing organism or “photobiont,” either an alga or cyanobacterium. They are able to live in a wide range of environments, including some of the most hostile on the planet such as the arctic tundra and hot, sandy deserts.

The symbiotic nature of lichens was discovered in 1867 by the Swiss botanist Simon Schwendener. Since that time, and especially with the advent of new molecular technologies, research has shown that the nature of the symbiosis is far from the simple picture of one algal species in partnership with a single fungus.

A lichen is not a simple plant or fungus but a partnership of at least two organisms growing together. Lichens combine a fungus and a “photobiont,” either algae or cyanobacteria, which together form a new organism such as the rock tripe lichen. While ordinary fungi get nutrition by decomposing dead organic material, such as rotting wood, the fungi in lichens are fed by the carbohydrates produced by their photobiont. “Lichens are fungi that have discovered agriculture,” according to lichenologist Trevor Goward.

Recent research has shown that lichen symbiosis is not as clear-cut as it first seemed. For example, the same lichen species can involve different algal partners depending on its geographic location. Recently scientists have discovered a third partner in many lichen species: single-celled basidiomycete yeasts embedded in the lichen’s cortex ("skin"). This other species most likely produces chemicals that help lichens ward off predators and repel microbes.

Did you know? Many (but not all) lichens are very sensitive to air quality as they have no roots and very efficiently absorb elements from the air. Lichens have been used to monitor air quality since the late nineteenth century when the increase in industrial pollutants, particularly sulphur dioxide, led to the decline of lichens around urban areas.

Food is the primary human use for rock tripe lichens, although some species are also used for fabric dye. However, rock tripe and other lichens are not to be considered an agricultural product. Because they grow very slowly, they are not commercially farmed, but rather are “foraged” from the wild.

In North America, rock tripe lichens are viewed as an emergency survival food, but in other countries they are viewed as a delicacy. “Tripe” is the culinary name for a ruminant’s stomach (typically beef), and is usually cooked by boiling for several hours. George Washington’s troops were said to have gathered and boiled rock tripe for soup at Valley Forge, Pennsylvania, during the winter of 1777–78.

The common name in French is tripe-de-roche, the exact translation of the English. It was eaten as survival food by French Canadian settlers and traditionally boiled in soups by the Cree and other Native Canadians. In Japan, rock tripe (Umbilicaria esculenta) is called iwa-take, or "rock mushroom." They are harvested by foragers then either deep-fried or added to salads.

Did you know?

Beatrix Potter (1866-1943). Credit: Wikimedia Commons. Public Domain

The author Beatrix Potter (1866–1943) was also a naturalist who was particularly interested in fungi and lichens. She was one of the first to recognize the lichen’s symbiotic nature. Although it was never published, her paper on fungi “On the Germination of the Spores of Agaricineae” was presented to the Linnean Society in London in 1897. Because the Linnean Society did not admit women to meetings at that time, it was read on her behalf by George Massee, a mycologist at the Royal Botanic Gardens at Kew.

Browse

Encyclopedia of Life Rock Tripe web page

Biodiversity Heritage Library Rock Tripe Resources

Read

Detailed information on lichens, written for hikers on the Hiker’s Notebook website 

Popova, Maria. Brain Pickings. Beatrix Potter, Mycologist: The Beloved Children’s Book Author’s Little-Known Scientific Studies and Illustrations of Mushrooms