Rock Greenshield Lichen

Also known as Baltimore Greenshield Lichen

Rock greenshield lichens spread across non-calcareous boulders and shaded rock faces, forming broad, pale yellow-green rosettes that cling tightly to the stone. Their upper surface is characterized by distinctive pustule-like outgrowths that fragment easily, dispersing symbiotic algal cells and fungal hyphae together to establish new colonies. Highly enduring yet slow-growing, individual colonies can persist on stable stone surfaces for many decades while slowly weathering the minerals beneath them.