About Umbilicaria mammulata (Ach.) Tuck.
Umbilicaria mammulata (Ach.) Tuck. is one of the largest lichen species in the world. Its thallus typically grows between 4 and 15 centimeters (1.6 to 5.9 inches) in diameter, though specimens as large as 63 centimeters (2.07 feet) have been recorded in the Smoky Mountains of Tennessee. The smooth upper surface of the thallus ranges in color from reddish-brown to grayish-brown, while the lower surface is solid pitch black. This lichen grows on boulders and steep rock walls, located within forests and around lakes. It can colonize multiple types of rock substrate, including acidic rock, sandstone, quartz, and granitic rock. Like most lichens, Umbilicaria mammulata is sensitive to air and water quality. When growing conditions are optimal, it is not unusual to find rocks or cliffs completely covered in dinner plate-sized thalli of this species. Research suggests that this species is more sensitive to the frequency and duration of precipitation than it is to pH levels and water quality.
