Plants annual. Culms 15-60 cm, erect or geniculate at the base,
branching at most of the nodes. Leaves cauline; sheaths usually
shorter than the internodes, glabrous or sparsely pilose; collars glabrous;
ligules less than 0.5 mm; blades 3-10 cm long, 1-2 mm wide, flat
to folded basally, involute distally, scabridulous on both surfaces, occasionally
sparsely pilose adaxially, light green. Inflorescences paniculate or
racemose, 2-11 cm long, to 1 cm wide; nodes glabrous or strigillose;
primary branches 1-2 cm, appressed, without axillary pulvini, with 1-2
spikelets. Spikelets partly overlapping, often in pairs, 1 spikelet subsessile,
the other pedicellate. Glumes 1-veined, light gray to dark purplish or
brownish; lower glumes 3-8(10) mm, from 1/2 as long as the upper glumes
to nearly equaling them; upper glumes 4-13 mm; calluses 0.3-0.5
mm; lemmas 3-11 mm, light gray to purplish, frequently mottled, midveins
scabrous, elsewhere glabrous, scabridulous, or sparsely appressed-puberulent,
junction with the awns not evident; central awns 3-8 mm, coiled at the
base, spreading distally; lateral awns 1-4 mm, straight, erect; anthers
3 and 2-3 mm, or 1 and about 0.25 mm. Caryopses light brown. 2n
= unknown.
Aristida dichotoma grows in sandy fields and clearings, disturbed sites
and sterile ground, pine woods, and on granitic outcrops of the United States
and southern Ontario. The two varieties have similar ecological preferences
and extensive overlap in their ranges, but var. curtissii is somewhat more western in its distribution.
Aristida dichotoma is similar to A.
basiramea, differing in its shorter lateral awns. Further study may
show that the two should be treated as conspecific varieties.
Tufted annual 2-4 dm, erect or ascending, branched from the base; lvs filiform, mostly involute, or the lower flat; terminal panicle 3-8 cm, very slender, often reduced to a raceme; lateral infls much shorter, mostly enclosed in the subtending sheaths; glumes subequal, mucronate, 1-veined, 5.2-10.5 mm; lemma 4.4-9 mm; central awn 3-10 mm, its base nearly horizontally divergent and loosely coiled, usually in a half to one full turn; lateral awns straight, erect, 0.7-3.3 mm. Dry sandy or sterile soil; Me. to Mich., Io., 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.