Plants cespitose, with caudices or with rhizomes up to 2 mm thick. Basal
rosettes well-differentiated; blades 1-14 cm long, to 22 mm wide,
ovate to lanceolate. Culms 20-75 cm, erect or decumbent to sprawling,
often purplish; nodes and internodes glabrous or puberulent to
pubescent; fall phase initially nearly erect, often sprawling eventually,
branches initially erect and apparently dichotomous, later rebranching, blades
and secondary panicles smaller than those of the culms. Cauline leaves
4-6; sheaths not overlapping, often glaucous, purplish, or olivaceous,
glabrous or puberulent, margins usually ciliate; ligules about 0.3 mm,
membranous, ciliate, cilia longer than the membranous portion, rarely with adjacent,
about 12 mm hairs; blades 5-16 cm long, 5-25 mm wide, linear to ovate-lanceolate,
glabrous or puberulent, with 9-13 major veins and 30-80 minor veins, bases cordate-clasping,
often asymmetrical, with papillose-based marginal cilia. Panicles 5-12
cm long, 3-10 cm wide, open, exserted; branches flexuous. Spikelets
2.2-3.2 mm long, 1.1-1.3 mm wide, ellipsoid, yellowish-green or purplish, pubescent.
Lower glumes 0.7-1.8 mm; upper glumes and lower lemmas
equaling or slightly shorter than the spikelets; lower florets sterile;
upper florets often minutely umbonate. 2n = 18.
Dichanthelium commutatum is fairly common in dry to wet, semi-open woodlands.
Its range extends from the eastern United States to South America. The primary
panicles are open-pollinated and are produced from April through June; the secondary
panicles are primarily cleistogamous and are produced from June through fall.
The four subspecies are fairly distinct in some parts of their
ranges, but subsp. commutatum
intergrades with the other three where they occur together.
Plants from loose caudices or with knotty or loose rhizomes. Culms decumbent
or sprawling, glabrous, sometimes glaucous, sometimes purplish. Basal blades
large, usually 8-14 cm long, 7-22 mm wide. Cauline blades 8-25 mm wide,
4-8 times longer than wide, thin, ovate-lanceolate, often glaucous, strongly
asymmetric-falcate. Spikelets 2.9-3.2 mm. Lower glumes about 1/4
as long as the spikelets; lower lemmas pointed.
Dichanthelium commutatum subsp. joorii grows in wet woodlands and
swamps. Its range extends into Mexico.