Herbs, annual, cespitose. Culms to 30 cm, bases soft. Leaves spreading to ascending, ¼–1/3 length of scapes; sheath borders tan, backs prominently ribbed, glabrous; blades filiform, 0.5 mm wide, involute, margins ciliate-scabrid, surface glabrous. Inflorescences solitary or more commonly in simple, open, rarely compact, involucrate anthelae; scapes filiform (rarely with several spikelets sessile or subsessile at plant base), prominently ribbed, glabrous; proximalmost involucral bract cuspidate or setaceous bladed, exceeding or exceeded by inflorescence. Spikelets red-brown, ovoid to lanceoloid, 3–5 mm; fertile scales ovate, 1.5–2 mm, apex acute, glabrous or distally puberulent, keel prominent, short-excurrent. Flowers: stamens (1–)2; anthers oblong-elliptic, 0.5–0.7 mm. Achenes yellowish to pale brown, trigonous-obovoid, 1 mm, faces rugose. 2n = 84.
Phenology: Fruiting summer–fall.
Habitat: Sandy savanna, prairie, arenaceous outcrops, sandy or gravelly waste areas
Elevation: 0–3000 m
N.B., N.S., Ont., Que., Ala., Ariz., Ark., Calif., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.H., N.J., N.Mex., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Vt., Va., W.Va., Wis., Mexico, West Indies, Central America, South America, Asia, Pacific Islands.
A specimen of Bulbostylis capillaris collected by E. Hall (585) gives Oregon without a specific locality.
Bulbostylis capillaris is distributed over a broad range of physiographic types and occurs in many forms, the most distinctive of ours being var. crebra, which has, in addition to numerous longscaped anthelae, large numbers of spikelets at the plant base.