Isoetes butleri, commonly known as limestone quillwort, is a species of plant in the quillwort family, a member of the lycophytes.
It is native to the eastern United States, where it is scattered and local. It is found almost exclusively on seasonally wet alkaline soils.[1] Common habitats include rocky prairies and glades, most often over limestone.[2] This species is inconspicuous and easily overlooked, due to its superficial similarity to a vegetative grass or sedge.[3]
The leaves of Isoetes butleri die back at the end of spring, when its habitat becomes hot and dry. It is then reduced to a below ground corm.[2]