in W. Aiton and W. T. Aiton, Hortus Kew. 1: 127. 1810.
Plants perennial, cespitose, 10–50 cm; rhizomes stoloniferous, slender. Culms erect to excurved, filiform, leafy, ± terete. Leaves shorter than culm; blades ascending, filiform, proximally to 1.5(–2)mm wide, apex trigonous, tapering, setaceous. Inflorescences: lateral spikelet clusters (0–)1–2, distant, terminal cluster ellipsoid to broadly turbinate or hemispheric, branches ascending; leafy bracts setaceous, overtopping clusters. Spikelets red-brown to deep brown, lanceoloid, (4–)5–6(–7) mm, apex acute; fertile scales lanceolate, 4–5(–6) mm, apex acuminate, midrib often excurrent as awn. Flowers: bristles 5–6, longest reaching at least past tubercle base, mostly to tip or beyond, antrorsely barbellate. Fruits 2(–3) per spikelet, (2.3–)2.5–2.6(–3) mm with pedicellar joint, receptacle, and tubercle; body lustrous, pale brown to deep brown, obovoid to ellipsoid, lenticular, 1–1.5 × 1 mm, margins narrow, flowing to tubercle; surfaces longitudinally finely lined, transversely very finely ridged with wavy rows of very narrow, vertical lattices, sometimes also with lines of shallow pits; tubercle triangularsubulate, (0.7–)1–1.3(–1.5) mm, base lunate, margins setulose proximally.
Phenology: Fruiting summer–fall.
Habitat: Sands and peats of pond shores, bogs, and seeps
Elevation: 0–400 m
N.B., Nfld. and Labr., N.S., Ont., Que., Sask., Conn., Del., Ill., Ind., Maine, Md., Mass., Mich., Minn., N.H., N.J., N.Y., Pa., R.I., Vt., Wis., Europe.