Digitaria cognata is a species of grass known by the common names fall witchgrass,[1] Carolina crabgrass,[2] and mountain hairgrass.[3]
This grass is a perennial without rhizomes. The roots are shallow. The erect stems grow up to 56 centimeters tall. The stem bases are tough and hairy.[1] The leaves are up to 12.6 centimeters long.[4] They are narrow, with "one side wavy, and the other smooth".[2] The inflorescence is a purple-tinged panicle with single-flowered spikelets.[2]
This grass provides graze for livestock and wild ungulates, and birds eat the seeds.[2]