5. Eleocharis erythropoda Steud.

Pl. 75 c, d; Map 278

E. calva Torr.

Plants perennial, with rhizomes, forming loose colonies. Aerial stems 10–50(–70) cm long, 0.5–1.5 mm wide, firm, wiry, and more or less circular in cross-section, lacking cross-lines. Basal sheaths usually tinged reddish purple or brown, less commonly straw-colored, sometimes darkened along the margin, the tip firm, truncate or slightly oblique. Spikelets 5–17 mm long, lanceolate to narrowly ovate in outline, the tips mostly sharply pointed, with 1 sterile, basal scale encircling the stem. Scales 1.8–2.5 mm long, ovate to broadly ovate, the tips rounded to bluntly pointed, light brown to dark brown, sometimes tinged reddish purple or with a green midrib, the margins sometimes white-membranous. Perianth bristles 4–6, less commonly none, shorter than to slightly longer than the fruit, retrorsely barbed. Stigmas 2. Fruits with the main body 1.0–1.7 mm long, broadly obovate in outline, biconvex to nearly circular in cross-section, the surface finely roughened to nearly smooth, yellow, turning to dark brown at maturity, shiny. Tubercles 0.2–0.4 mm long, narrowly conical to somewhat flattened. 2n=18. May–September.

Scattered throughout the state (northeastern U.S. and adjacent Canada west to Nebraska). Margins of ponds, lakes, sloughs, swampy forests, streams, and ditches, sometimes in shallow water; also in bottomland prairies and moist depressions of upland prairies.

For a discussion of a hybrid between this species and E. compressa, see the treatment of that species. Eleocharis erythropoda is a member of the E. palustris complex, and its relationship to the rest of this complex is discussed under the treatment of E. palustris.