Eleocharis geniculata (L.) Roem. & Schult.

The name Eleocharis caribaea (Rottbøll) S. F. Blake is considered by most contemporary authorities to be misapplied (K. L. Wilson 1990). Eleocharis geniculata has been reported from South Carolina; I have not seen a voucher.

Plants tufted, without creeping rhizomes. Culms to 45 cm × 0.2–1 mm. Leaves: distal leaf sheaths persistent, firm, distally tightly sheathing, apex acute. Spikelets orbicular to ovoid, 1–9 × 1–4 mm, apex rounded to acute; proximal scale without flower, not amplexicaulous; floral scales to 125, 11–14 per mm of rachilla, tightly appressed, dark red-brown to stramineous, ovate to elliptic, 0.8–3 × 0.6–2(–2.3) mm, membranous to cartilaginous, apex rounded to acute. Flowers: perianth bristles (0–)4–8, typically 7, red-brown, rarely whitish, vestigial to much exceeding tubercle, typically equaling achene, spinules few to dense; styles 2-fid. Achenes brown ripening to black, biconvex, orbicular to obpyriform, 0.5–1.1 × 0.3–0.7 mm, apex rarely constricted proximal to tubercle, very finely reticulate at 40X. Tubercles stramineous to whitish, umbonate to subconic, 0.2–0.4 × 0.2–0.5 mm, apex rounded to acute. 2n = 10.

Tufted annual, 12-25 cm. Roots white, fibrous. Stem 0.5-1 mm diam., green, with 5-6 obtuse angles separated by deep grooves. Open sheaths c. 5 mm, wide, scarious; lower closed sheath to 15 mm, reddish brown or green, mouth oblique, upper to 50 mm, green or basal parts reddish, with 5 nerves, mouth oblique, margin narrowly scarious; blades 0 or minute tip. Spike 3-6 x 3-4 mm, ovoid or globular, with 50 or more very closely imbricating glumes; basal glume fertile, not distinct from other glumes or its mid-nerve more pronounced and stronger; glumes 1.7-2.2 mm, not in protruding spiral rows, cymbiform, rounded, mid-nerve not very distinct, not reaching apex, sides grey brown, margins narrowly scarious. Perianth bristles 6-8, as long as or longer than nut, brown; stamens 2-3, anthers 0.5-0.7 mm; stigmas 2. Nut 0.8-1 x 0.6-0.8 mm (excl. stylopodium), obovoid, bi-convex, apex rounded, basal part gradually tapering, obscurely reticulate, glossy, finally black; stylopodium 0.1-0.2 x 0.3-0.4 mm, much wider than long, white, clearly constricted from nut.

Ont.; Ala., Ariz., Calif., Fla., Ga., Ill., Ind., La., Mich., Miss., Nebr., Nev., N.Mex., Ohio, Okla., Pa., Tex.; Mexico; West Indies; Bermuda; Central America; South America; Asia; Africa; Pacific Islands.

Distribution: Pantropical extending into subtropics; Europe (Italy), Africa, Madagascar, Egypt, from Iraq to Pakistan, India, China, Taiwan, Malaysia, Australia, N and S America.

Fl. Per.: April -June.

Fruiting spring–winter (Mar–Dec).

Brackish creeks, canal banks, dune depressions, hammocks, irrigation ditches, lakeshores, lagoons, mangrove thickets, maritime mud flats, ditches, salt marshes; 0–1500m.

Rice fields, marshlands, wet meadows.

Scirpus geniculatus Linnaeus, Sp. Pl. 1: 48. 1753; Eleocharis capitata R. Brown; E. caribaea (Rottbøll) S. F. Blake; E. dispar E. J. Hill

Scirpus geniculatus L., Sp. Pl. 1: 48. 1753; E. caribaea (Rottb.) Blake in Rhodora 20: 24. 1918; Scirpus caribaeus Rottb., Descr. Pl. Rar.: 24. 1772; E. capitata R.Br., Prodr. 1: 225. 1810; C.B.Clarke in Hook.f., l.c. 627, non Scirpus capitatus L.; E. caduca (Del.) Schultes, Mantissa 2: 88. 1824; Scirpus caducus Del., Descr. Egypte, Hist. nat. 9 (1813 n.v.); K.M. Matthew, Fl. Tamilnadu Carnatic 4: pl. 654. 1988.