Scientific Name
Aristida purpurea Nutt. (Synonyms: Aristida fendleriana; Aristida longiseta)
Common Name(s)
Purple threeawn, Fendler threeawn, red threeawn, wiregrass, dogtown grass, prairie threeawn
Tribe / Family Name
Aristideae
Flowering Period
June to September
Symbol
ARPU9
Description
Purple threeawn is a native warm-season perennial bunchgrass that reproduces from seeds and tillers. Culms range from 10–100 cm in height. Its inflorescence is usually a sparingly branched panicle, occasionally racemose, 5-30 cm long, up to 12 cm wide with erect or flexuous branches, and often purplish or reddish. Spikelets are 10–18 mm long (excluding awns) and 1-flowered; disarticulation above the glume. Glumes are linear-lanceolate, glabrous or scabridulous, 1-nerved, acuminate, occasionally awn-tipped (up to 1 mm long), and usually unequal (lower glumes 4-12 mm long; upper glumes 7–25 mm long). Lemmas are 6–16 mm long (including awn column), linear, faintly 3-nerved, and gradually tapering into three-branched (trifid) awns (awns usually 13–140 mm long and spreading at maturity); callus is short-bearded and sharp. Sheaths are open and glabrous to weakly scabrous with collars usually sparsely pilose on both sides. Auricles are absent. Ligules are a fringe of hairs and less than 0.5 mm long. Blades are 4–25 cm long, up to 1.5 mm wide, involute or rarely flat, lax or curled at maturity, mostly basal, gray-green, glabrous or occasionally scaberulous to hirsute adaxially, and sometimes scabridulous abaxially.
General Info
Purple threeawn can be found in open, dry disturbed sites, wastelands, roadsides, rangelands, rocky areas, foothills, grasslands, and desert plains.
Similar Species
Purple threeawn is unique and is not easily confused with other grasses. It is the only grass that has three branched (trifid) awns arising from the tip of the lemmas.
Picture of growth habit.
Inflorescences usually a sparingly branched panicle, occasionally racemose.
Close-up picture of spikelet.
Close-up picture of ciliate membrane ligule.
Illustration of purple threeawn. USDA-NRCS PLANTS Database / Hitchcock, A.S. (rev. A. Chase). 1950. <i>Manual of the grasses of the United States</i>. USDA Miscellaneous Publication No. 200. Washington, DC.