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 triangular subulate, (0.7-)1-1.3(-1.5) mm, base lunate, margins setulose proximally. Fruiting summer-fall. Sands and peats of pond shores, bogs, and seeps; 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.
