Perennial herb with slender rhizomes, mat-forming 8 - 45 cm tall Leaves: reduced to bladeless sheaths, basal, two per culm, margins fused and enclosing culm, not splitting, red basally, reddish brown at the apex, papery, with a blunt to nearly truncate (cut straight across) apex. Flowers: minute, spirally arranged on the axis of the spikelet, lacking sepals and petals, with zero to five bristles, subtended by a scale. Bristles (when present) straw-colored, equal to or shorter than the achene. Stamens three, exserted. Anthers orangish brown to yellow, to 2 mm long. Pistil one. Style three-cleft, or some two-cleft. Fruit: a one-seeded achene, yellowish brown to dark brown, 1 - 1.5 mm long, to 0.8 mm wide, reverse egg-shaped to reverse pear-shaped, three-angled (nearly equilaterally to compressed), some convex on both sides, finely wrinkled, sometimes finely latticed. Tubercle brown to whitish, tiny, pyramidal, often depressed. Seed with a thin, non-adherent wall. Culm: unbranched, 8 - 45 cm long, 0.5 - 1.8 mm wide, compressed to two to five times as wide as thick, often twisted, two- to twelve-ridged, spongy, enclosed basally by two fused sheaths. Spikelets: solitary, 4 - 8 mm long, 2 - 4 mm wide, egg-shaped with a pointed apex, with 20 to 60 floral scales. Scales spirally arranged and overlapping, brown to dark brown with a paler midrib, sometimes colorless or straw-colored, hyaline towards the apex, 2 - 3 mm long, 1 - 1.5 mm wide, egg-shaped with a pointed apex, some becoming two-cleft or torn-looking with age.
Similar species: No information at this time.
Flowering: late April to mid-June
Habitat and ecology: Occasional, especially in the southwestern sector of the Chicago Region. Found in moist to mesic areas of calcareous prairies.
Occurence in the Chicago region: native
Etymology: Eleocharis comes from the Greek words heleios, meaning "dwelling in a marsh," and charis, meaning grace. Compressa means compressed.