Plants perennial; cespitose. Culms 25-120 cm, wiry, erect to sprawling,
unbranched. Leaves basal and cauline; sheaths usually longer than
the internodes, glabrous; collars glabrous or strigillose; ligules
less than 0.5 mm; blades 5-40 cm long, 1-2.5 mm wide, flat to folded, straight
to lax at maturity, adaxial surfaces with scattered, 1.5-3 mm hairs near the ligule.
Inflorescences paniculate, 15-40 cm long, (8)10-35(45) mm wide; rachis
nodes glabrous or strigillose; primary branches 5-25 cm, remote, stiffly
ascending to divaricate, with axillary pulvini, usually naked near the base; secondary
branches and pedicels usually appressed. Spikelets usually congested.
Glumes subequal, 9-15 mm, 1-veined, acuminate; calluses 1-1.2 mm;
lemmas 9-15 mm long, smooth to tuberculate-scabrous, narrowing to slightly
keeled, usually not twisted, 0.1-0.2 mm wide apices, junction with the awns not
evident; awns unequal or almost equal, not disarticulating at maturity;
central awns 8-25(30) mm, straight to arcuate at the base; lateral awns
absent or to 0-23 mm; anthers 3, 1.2-2.4 mm. Caryopses 6-8 mm, light
brownish. 2n = 22, 24.
FNA 2003, Gould 1980
Common Name: spidergrass Duration: Perennial Nativity: Native Lifeform: Graminoid General: Coarse, tufted perennial grass; culms erect to sprawling, 25-120 cm; flowers in first season; roots tough and wiry. Vegetative: Sheaths usually longer than the internodes, glabrous; collars glabrous or strigillose; ligules glabrous or with a sparse tuft of loose hairs; leaf blades firm, narrow, involute on drying, 5-40 cm long, 1-3 mm wide, upper surface glabrous or with short, ro Inflorescence: Openly branched panicles 15-40 cm long, 10-35 mm wide, branches spreading to approximately 90 degrees; branchlets and spikelets conspicuously appressed along the primary branches; spikelets with one floret each; glumes subequal (spikelets at first often showing only one glume, lower glume develops with age); lemma tapering to short, stout, scabrous, straight or only slightly twisted awn column; junction with the 3 awns not evident; awns unequal or almost equal, not disarticulating at maturity; to 25 mm long. Ecology: Found on rocky slopes and plateaus, as well as disturbed soils from 2,500-5,500 ft (762-1676 m); flowers summer. Distribution: c to s CA, west to TX; south through MEX to South America. Notes: Distinguished by being an erect, perennial three-awn bunchgrass with an open panicle, the branches possessing axillary pulvini (small appendages in the axils which force the branches open). The spikelets and pedicels are often appressed to the open panicle branches and the lateral awns are often slightly shorter than the central awn or even absent, the central awn being straight and not bent. Recognized as two varieties in the region: var. gentilis has an 3 well developed awns with the two lateral ones shorter than the central. Var. ternipes has one well-developed awn and the other two highly reduced to absent. Ethnobotany: Unknown Etymology: Aristida is from the Latin arista for awn, while purpurea is Latin for purple, ternipes is from Latin terni, three and the suffix -pes referring to the stalk. Synonyms: None Editor: SBuckley 2010, FSCoburn 2014, AHazelton 2015