Capitate Spike Rush

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.

Eleocharis caribaea (Rottb.) Blake, Rhodora 20 : 24. 1918.
Scirpus geniculatus L. Sp. PI. 48. 1753, in part. Not 5". geniculatus L. Sp. PI. ed. 2. 71. 1762.* Scirpus caribaeus Ro ttb. Descr. PI. Rar. 24. 1772. (West Indies.)
* See note under E. elegans. Scirpus geniculattts minor Vahl, Enum. 2: 251. 1805.
Eleocharis capitala R. Br. Prodr. 225. 1810. (Australia.)
Eleocharis setacea R. Br. Prodr. 225. 1810. (Australia.)
Eleocharis geniculata R. & S. Syst. Veg. 2: 150. 1817.
Eleocharis caditca Schultes in R. & S. Syst. Veg. Mant. 2 : 88. 1824. (Egypt.)
Scirpus Brownii Spreng. Syst. 1 : 204. 1825.
Eleogetnis capitatus Nees in Wight, Contr. Bot. Ind. 112. 1834.
Eleocharis microforniis Buckl. Proc. Acad. Phila. 1862 : 10. 1862. (Northern Texas.)
Eleocharis dispar E. J. Hill, Bot. Gaz. 7: 3. 1882. (Indiana.)
Chlorocharis capitata Rikli, Jahrb. Wiss. Bot. 27 : 564. 1895.
Eleocharis capitata var. dispar, Fernald, Rhodora 8: 129. 1906.
Eleocharis caribaea var. dispar Blake, Rhodora 20: 24. 1918.
Eleocharis caribaea var. Stokesii F. B. H. Brown, Bishop Mus. Bull. 84: 106. 1931. (Polynesia.)
Cespitose ; culms firm, 0.3-4 dm. high, striate and sulcate ; sheaths prominent, stramineous, usually with a brown base and a firm, oblique, often attenuate apex ; spikelets subglobose or ovoid, obtuse, many-flowered ; scales ovate-orbicular, almost cartilaginous to membranous, yellow to pale brown ; style bifid ; stamens 2 or 3 ; achene obovoid, 0.7-1 mm. long, lustrous-black to purplish, the spongy, whitened style-base variable in shape but usually much depressed; bristles 6-8, coarse, brown, exceeding the achene or occasionally lacking.
Type locality : Jamaica.
Distribution : South Carolina, Florida, Texas, California, Indiana, Michigan, Ontario ; tropics of the Old and New Worlds. The most widely distributed species of Eleocharis.

Eleocharis sintenisii Bock. Beitr. Cyp. 1 : 16. 1888
Eleocharis Shaferi Britton, Mem. Torrey Club 16 : 59. 1920. (Oriente, Cuba.)
Eleocharis yunquensis Britton; Britton & Wilson, Sci. Surv. Porto Rico 5: 92. 1923. (Puerto
Rico.) Heleocharis Ekmanii Kiikenth. Repert. Sp. Nov. 23 : 192. 1926. (Cuba.) Heleocharis debilis f. macra sensu Kiikenth. Repert. Sp. Nov. 23 : 192. 1926. (Brazil.)
Rootstocks wide-creeping to matted-lignescent ; culms filiform, O.S-3 dm. long, often short and rigid, irregularly sulcate ; sheaths stramineous to purple, the apex acute, not inflated ; spikelets usually few-flowered, elliptic-lanceolate to ovate, obtuse to acute ; scales obtuse to subacute, stramineous to purple, often with a green midrib ; stamens 2 or 3, anthers 0.4-0.7 mm. long; style bifid; achenes lenticular, narrowly obovoid, 0.9-1.5 mm. long, shiningblack ; style-base conic to subulate ; bristles light brown to white, equaling or exceeding the achene.
Type locality : "Prope Bayamon ad Palo Seco in fossis," Puerto Rico.
Distribution: Cuba; Puerto Rico.

Eleocharis geniculata is a species of spikesedge known by several common names, including bent spikerush and Canada spikesedge. This is a widespread plant of wet areas in the Americas, Asia, Africa, Australia, Madagascar, and some Pacific Islands. It is an annual spikesedge growing to a maximum height of about 40 centimeters. It has a few straw-colored leaves and many thin erect stems. The stems hold inflorescences of rounded spikelets each containing at least 10 tiny flowers. The flowers are covered with dark greenish-brown bracts. The fruit is a shiny purple-brown achene not more than a millimeter long.