Culms 26-60 cm. Blades 3-17 cm, basal and cauline, involute. Panicles 10-25 cm; primary branches appressed at the base, without axillary pulvini, capillary, drooping to sinuous distally; pedicels capillary, usually lax to sinuous. Lower glumes 4-9 mm; upper glumes 7-16 mm; lemmas 6-12 mm long, narrowing to 0.1-0.3 mm wide; awns subequal, (15)20-60 mm long, 0.1-0.3 mm wide at the base. 2n = 22, 44, 66, 88.

Aristida purpurea var. purpurea grows in sandy to clay soils, along right of ways, or on dry slopes and mesas. Its range extends from the Flora region to Mexico and Cuba. As treated here, var. purpurea is, admittedly, a catch-all taxon, incorporating slender plants with small spikelets that used to be referred to A. roemeriana Scheele, but also occasional plants with somewhat flexible branches that are intermediate to var. wrightii and var. nealleyi.

Common Name: purple threeawn

Duration: Perennial

Nativity: Native

Lifeform: Graminoid

General: Erect and stout to spreading and delicate stems 25-60 cm.

Vegetative: Blades basal and cauline 3-17 cm, involute.

Inflorescence: Panicles usually nodding, purplish to greenish, branches capillary, drooping to flexuous, 8-20 cm, primary branches appressed at base; glumes unequal, reddish, lower 4-9 mm, the upper 7-16 mm, lemmas 6-12 mm long, narrowing to 0.1-0.2 mm wide, awns subequal, 20-60 mm long, 0.1-0.2 mm wide.

Ecology: Found on sandy to rocky flats among desert grassland or scrub, often in calcareous soils from 1,500-5,000 ft (457-1524 m); flowers March-June.

Distribution: s CA, NV, s UT, CO, AZ, NM, TX, OK; south through MEX.

Notes: Referred to as a -catch-all- taxon, incorporating the slender stems with small spikelets which were previously treated as A. roemeriana and plants with flexible branches intermediate to var. wrightii and var. nealleyi. Distinguished from other varieties by the tight tufts of tightly-rolled, erect blades from the base; appressed infl. branches; Awns 8-35 mm; and the panicle branches which droop towards the tip.

Ethnobotany: Unknown

Etymology: Aristida is from the Latin arista for awn, while purpurea is Latin for purple.

Synonyms: Aristida purpurea var. laxiflora, A. roemeriana

Editor: SBuckley 2010, FSCoburn 2015