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.
B.C., N.B., N.S., Ont., P.E.I., Que., W.Va., Del., D.C., Wis., Ala., Kans., Ohio, Okla., Ark., Ariz., Conn., Fla., Ga., Iowa, Idaho, Ill., Ind., Ky., La., Mass., Md., Maine, Mich., Minn., Mo., Miss., N.C., N.Dak., Nebr., N.H., N.J., N.Mex., N.Y., Pa., R.I., S.C., S.Dak., Tenn., Tex., Va., Vt., Calif.
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.