Rock Tripe

In the nearby Oaklands Town Forest, huge boulders lie strewn about by the hand of the last glacier. Named for the many red oaks that grow in this undulating woodland, it could also be called boulderlands, so prominent is this feature. Covering many of the biggest boulders is rock tripe, or as French Canadians might call it tripe de roche, meaning "rock guts."

Huge boulders covered in rock tripe
at Oaklands Town Forest, Exeter, New Hampshire

This green (above) and black (beneath) lichen grows slowly on the steep sides of boulders and cliffs. From afar it looks like a bunch of dead leaves glued to the rocks like an art project. Up close it resembles a bed of leathery leaf lettuce. Rock tripe soaks up moisture from their air; during dry periods it becomes brittle. Regular rain this fall has kept trails muddy and the rock tripe moist and pliable.

Being a lichen, rock tripe is a partnership between a fungus, which gives form and color, and an alga, which cooks up the meals for the pair through photosynthesis. The Latin name for rock tripe, Umbilicaria mammulata, stems from its single point of attachment to the rock -- similar to an umbilical cord. Hence the other common name for this species, navel lichen.

A large, tortilla-sized rock tripe;
note the "navel,"
its point of attachment to the boulder

Rock tripe can be considered an extreme food, eaten only in an emergency. Many are said to have eaten it when starvation was the alternative -- Washington's troops at Valley Forge, Canadian trappers, Franklin's expedition to map the Northwest passage through northern Canada. Unless cooked carefully, it is known to cause cramps, or worse, and may be on par nutritionally with old shoe leather. Native peoples used it to thicken broth. Rock tripe is not to be confused with the other tripe - the lining of cow stomachs that can also be eaten, but also with much care in its preparation.

Another use of rock tripe, among other lichens, is as a dye. In an article, Local Color: Finding Wild Sources for Dye in the Forest in Northern Woodlands magazine, Allaire Diamond writes about Anne Williams who maintains a lichen dye bath in her garage. Anne ferments rock tripe in a solution of ammonia and water for 12 months to get an intense purple dye. She recommends how to harvest the tripe with care, mostly taking only the "leaves" that have sloughed off the rock.

Walk up to the nearest tripe-covered boulder and gently pull on one of the leathery disks. The rock tripe is attached like super glue, but pulling too hard will break the umbilical cord. Best to leave the tripe to continue its slow growth on these giant boulders.