Plants annual; tufted, delicate. Culms 15-60(70)
cm, erect to decumbent, wiry. Sheaths often inflated, sometimes with
sparse hairs basally, hairs papillose-based, glabrous or the apices with small
tufts of hairs, hairs to 3 mm; ligules 0.1-0.3 mm; blades 2-12(25)
cm long, 0.6-2 mm wide, flat to loosely involute, glabrous abaxially, scabridulous
adaxially, bases of both surfaces sometimes with a few papillose-based hairs,
margins smooth or scabridulous. Panicles terminal and axillary, 1-5 cm
long, 0.2-0.5 cm wide, contracted, cylindrical, enclosed in the uppermost sheath;
lower nodes with 1-2(3) branches; primary branches 0.4-1.8 cm,
appressed, spikelet-bearing to the base; secondary branches appressed;
pedicels 0.2-4 mm, appressed, scabridulous. Spikelets 2.3-6 mm,
yellowish to purplish- or grayish-mottled. Glumes subequal, linear-lanceolate
to lanceolate-triangular or ovate, membranous to chartaceous, glabrous; lower
glumes (2.2)2.8-4.7 mm; upper glumes (2.4)3-5 mm; lemmas (2.1)3-5.4
mm, lanceolate to lanceolate-triangular, 1-3-veined, chartaceous, often mottled
with purplish or grayish areas, strigose, hairs less than 0.5 mm, apices acuminate
or acute; paleas (2.1)3-6 mm, as long as or longer than the lemmas, sometimes
tapering into a beak, lanceolate to lanceolate-triangular, chartaceous, strigose;
anthers 3, 1.2-3.2 mm, yellowish or purplish. Fruits (1.1)1.8-2.7
mm, obovoid, laterally flattened, light brownish, translucent. 2n = 54.
Sporobolus vaginiflorus is a North American species, native to the eastern
portion of the Flora region and probably introduced in the west. It grows
in disturbed sites within many plant communities, commonly in sandy to sandy-clay
soils, these often derived from calcareous parent materials. Its elevational
range is 1-1250 m.