Plants perennial, mat-forming; rhizomes evident, 0.3-0.5 mm thick, hard, cortex persistent, longer internodes 2 mm, scales persistent or fugaceous, 2-3 mm, membranous to papery, slightly fibrous. Culms terete, 2-15 cm × 0.15-0.3 mm, firm to soft. Leaves: distal leaf sheaths persistent, not splitting, proximally stramineous to reddish, distally green or stramineous to reddish, membranous, apex often red, obtuse to acute, tooth absent. Spikelets ovoid, 1-4 × 1-2 mm, obtuse to acute; proximal scale amplexicaulous, apex entire; subproximal scale with flower; floral scales spreading in fruit, 5-30, 8 per mm of rachilla, medium to very dark brown, midrib region often pale or greenish, broadly ovate, 1-1.3 × 1 mm, apex rounded, entire, not carinate. Flowers: perianth bristles absent; stamens 3; anthers yellow, 0.3 mm; styles 3-fid. Achenes persistent after scales fall, to dark yellow-orange or brown, broadly obpyriform, trigonous, angles evident, 0.6-0.65 × 0.5-0.55 mm, rugulose at 20-30X, 20 blunt horizontal ridges in each vertical series. Tubercles brown, greatly depressed, rudimentary, 0.05-15 × 0.15-0.3 mm.

Fruiting late spring (Jun)-summer. Fresh bog pools, streams, disturbed places; 30-400 m; Nfld. and Labr., N.S., Ont., Que., Sask.; Alaska, Mich., Minn., N.H., Wis.

Eleocharis nitida is much like E. elliptica but all structures are smaller; intermediates are unknown.