Plants perennial; cespitose, bases knotty, without rhizomes. Culms 40-100 cm tall, 1-4 mm thick at the base, erect, branching at the base, shoots becoming thickened and somewhat fan-shaped upwards. Leaves cauline; sheaths mostly longer than the internode, mostly or completely glabrous, sometimes pilose, particularly along the margins and at the throat, remaining intact at maturity; collars glabrous or pilose; ligules about 0.2 mm; blades 10-25 cm long, 1-3 mm wide, usually flat, usually lax, sometimes sinuous to curling at maturity, glabrous, pale green, drying brownish. Inflorescences paniculate, (15)20-55 cm long, 0.5-2(3) cm wide, often nodding; nodes glabrous, sometimes scabrous, lower nodes usually associated with more than 2 spikelets; primary branches 1-5 cm, tightly appressed to loosely ascending, without axillary pulvini, with 1-8 spikelets. Spikelets appressed. Glumes 5-10 mm, lower glumes from 3/4 as long as to 1-4 mm longer than the upper glumes, glabrous or sparsely appressed-pubescent, 1-2-veined, 1-keeled, tan to purplish, unawned or the awns no longer than 1 mm; calluses 0.4-0.8 mm; lemmas 4-8 mm, glabrous, mostly light tan or gray, often spotted or banded, beak not twisted, junction with the awns not evident; awns 8-25 mm, equal or subequal in length, curved, arcuate, or spirally coiled at the base, not disarticulating at maturity; central awns sometimes thicker than the lateral awns, erect to arcuate-reflexed; lateral awns straight and erect, ascending, or divergent; anthers 1 or 3, 1-1.5 mm, brown. Caryopses 3-5 mm, chestnut brown. 2n = unknown.
Aristida purpurascens is composed of three intergrading varieties.
Lower sheaths shorter or longer than the internodes,
glabrous; blades usually about 1 mm wide, usually not curling. Glumes
subequal, 8-9 mm; awns 12-18 mm, of equal thickness, spirally contorted
at the base, divergent.
Aristida purpurascens var. tenuispica grows in pine and oak woods,
prairies, and along roadsides, at low elevations and usually in sandy soils.
Within the Flora region, it grows on the coastal plain from North Carolina
to Mississippi. It also grows in Mexico and Honduras.
Perennial 4-10 dm, tufted on a knotty base; lvs to 2 dm, mostly flat, 1-4 mm wide; lower sheaths covering the nodes, usually ±pilose; infl 1-2 dm, slender, loosely or densely spike-like, with short, ascending or appressed branches; glumes 1-veined, the first 8-14 mm, scabrous on the keel and sometimes on the sides, the second 6.5-11.5 mm, almost always exceeding the lemma and exceeded by the first glume; lemma 5.5-9.5 mm; awns about equally divergent, the central one 2-3.5 cm, the lateral 1.5-2.5 cm. Dry sandy soil and prairies; Mass. to s. Ont., Wis., and Kans., s. to Fla. and Tex.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.