Eleocharis atropurpurea (Retz.) J. Presl & C. Presl

Eleocharis atropurpurea has been reported from Colorado, Montana, and Virginia; I have not seen voucher specimens.

Plants tufted, without creeping rhizomes. Culms 2–12(–19) cm × 0.2–0.4 mm. Leaves: distal leaf sheaths firm, distally tightly sheathing, apex acute. Spikelets ovoid to ellipsoid, 2–6(–8) × 1–2.5 mm, apex acute; proximal scale with or without flower, not amplexicaulous; floral scales to 100, 15–19 per mm of rachilla, often loosely appressed, dark red-brown to stramineous, ovate to elliptic, 0.6–1.3 × 0.3–0.7 mm, membranous, apex rounded to acute. Flowers: perianth bristles (0–)4–6, typically 4, colorless to whitish, vestigial to 1/2 as long as achene, smooth or spinuliferous; styles 2-fid. Achenes black, obovoid, biconvex, 0.3–0.5 × 0.3–0.4 mm, apex often constricted proximal to tubercle, smooth at 40X. Tubercles stramineous to whitish, umbonate to subconic, 0.1–0.2 × 0.1–0.2 mm, apex acute. 2n = 20.

Annual, 2-15 cm, forming small tufts. Roots fibrous. Stem 0.3-0.5 mm diam., with 5-6 obtuse angles separated by deep grooves. Lower closed sheath 3-5 mm, brown or reddish, upper to 10 mm, green or grey green, base often reddish, with 5-6 green nerves, mouth oblique; blades 0 or tip c. 1 mm. Spike 2-7 x 1-3 mm, ovoid or globose, with c. 30 or more glumes in five spiral rows, all fertile; basal glume not distinct or slightly larger and with more pronounced mid-nerve than in other glumes; glumes 1.1-1.6 mm, cymbiform, with prominent, green mid-nerve not quite reaching obtuse apex, sides brown or dark reddish brown, nerves obscure or missing, margins more or less scarious. Perianth bristles rising from white collar, 4-7 or 0, to as long as nut, white or pale brownish; stamens 1-2, anthers 0.3-0.5 mm. Nut 0.6-0.8 x 0.5-0.6 mm, obovoid, bi-convex, apex rounded, basal part gradually tapering, obscurely or finely reticulate, finally black, glossy; stylopodium much wider than long, c. 0.1 x 0.3 mm, white, clearly constricted from nut.

B.C.; Ala., Calif., Fla., Ga., Iowa, Kans., La., Mich., Mo., Nebr., N.Mex., N.C., Okla., S.C., Tex., Wash.; Mexico; West Indies; Central America; South America; Europe (naturalized); Asia; Africa; Pacific Islands.

Distribution: Pantropical and extending into S Europe, Turkey, Iraq, Afghanistan, Pakistan, Tadjikistan, Uzbekistan, China, Japan; tropical Africa, Madagascar, India, Malaysia, Australia, N and S America.

Fl. Per.: September - October.

Fruiting summer–fall (Jun–Sep).

Canal banks, hammocks, irrigation ditches, lake and pond margins, maritime shores, rice fields; 0–1800m.

Rice fields, wet meadows, c. 500-900 m.

Scirpus atropurpureus Retzius, Observ. Bot. 5: 14. 1789

Scirpus atropurpureus Retz., Obs. Pl. 5: 14. 1789; E. lereschii Shuttlew., Flora 16: 241. 1837; Reichenb., Icon. Fl. Germ.8: Pl. 295, fig. 699. 1846. Blake in Proc. Roy. Soc. Queensland 50: Pl. 10, figs. 32-33. 1939.