Novon 11: 243, figs. 1F–J, 2. 2001.
Plants perennial, densely cespitose; rhizomes concealed by persistent culm bases, short, 4–5 mm thick, hard, cortex persistent, internodes crowded, scales decaying to coarse fibers, 1 cm, papery. Culms greatly compressed, 4–10 times wider than thick, often with 1 or 2 sharp ridges on 1 side, (8–) 20–35 cm × 0.7–2.3 mm, hard, finely striate, spongy. Leaves: distal leaf-sheaths persistent, not splitting, proximally red or stramineous, distally green to stramineous, inflated, papery, apex dark-brown, broadly obtuse to subtruncate, callose, tooth absent. Spikelets ovoid, 4–9 × 2.5–4 mm, apex acute; proximal scale clasping 2/3–3/4 of culm, apex 2-fid; subproximal scale empty or with a flower; floral scales spreading in fruit, 30–60, 6–9 per mm of rachilla, medium or pale-brown, midrib region often paler, ovatelanceolate, 2.5–3.5 × 1.5 mm, apex 2-fid, carinate in distal part of spikelet. Flowers: perianth bristles 0 (–5), stramineous to pale-brown, 1/2 of to equaling achene length; stamens 3; anthers orangebrown, 0.7–1.5 mm; styles 3-fid. Achenes falling with scales, yellowbrown to medium brown, obovoid to obpyriform, nearly equilaterally trigonous, cross-section circular to slightly compressed, angles obscure or evident, 0.9–1.1 × 0.6–0.75, neck usually very short, finely rugulose at 10–30X, 20 or more low, blunt horizontal ridges in vertical series. Tubercles brown, depressed-pyramidal, often rudimentary, 0.1–0.25 × 0.2–0.3 mm.
Phenology: Fruiting spring–summer (May–Jun).
Habitat: Seasonally wet places on limestone, cedar (juniper) glades, stream beds, prairies, ditches
Elevation: 200–300 m
Ala., Ga., Ky., Tenn.
Eleocharis bifida was previously included in E. compressa. A very few specimens of E. compressa var. compressa from the states where E. bifida is known are like E. bifida except for their entire proximal floral scales and evident rhizomes.