Purple threeawn

Aristida purpurea, commonly known as purple threeawn, is a perennial bunchgrass in the Poaceae family native to North America, ranging across most of the western two thirds of the United States, southern Canada and northern Mexico, where it grows on dry plains, mesas, sandy slopes, roadsides and disturbed rangeland. The plant forms dense tufts of erect to slightly geniculate culms reaching 30 to 80 centimetres tall, often weakly branched at the base. The narrow, involute leaf blades are 5 to 25 centimetres long and 1 to 2 millimetres wide, with short membranous to ciliate ligules. The inflorescence is an open to contracted, often nodding panicle 5 to 20 centimetres long, frequently tinged purple, with slender flexuous branches. Each spikelet bears a single floret subtended by two narrow, awn-tipped glumes; the lemma terminates in three slender, divergent awns 2 to 10 centimetres long that are sharp, scabrid and capable of working into the eyes, nostrils and skin of livestock. The grain is a narrow, linear caryopsis enclosed within the persistent lemma. Several intergrading varieties are recognised across its wide range.