Sphenoclea zeylanica
Fruct. Sem. Pl. 1: 113, plate 24, fig. 5. 1788.
Herbs 18.5–97 cm. Stems ± terete, green, 2–10 mm diam. at mid stem, often proximally spongy and rooting from proximal nodes where submerged. Leaves: petiole 0.3–2.7 cm; blade 1–13.8 × 0.3–5.7 cm. Spikes narrowly ovoid to cylindric, 0.5–10.5 × 0.3–1.3 cm. Peduncles 0.4–10.3 cm. Flowers: calyx lobes broadly ovate to deltate, 1.2–1.5 × 1.5–1.8 mm, enlarging in fruit, obtuse to rounded, ± erose; corolla caducous, 1.8–2.3 mm, lobes oblong, length 1–2 times tube, apex obtuse to acute, ± erose; filaments 0.1–0.2 mm; anthers 0.5 × 0.6 mm; styles 0.3–0.4 mm; stigmas 0.4 mm diam. Capsules sessile, 2–3 × 3–4 mm, lids 3–4 mm diam. Seeds 0.4–0.5 mm. 2n = 24.
Phenology: Flowering Jun–Nov.
Habitat: Rice fields, ditches, shallow margins of ponds and lakes, stream banks, wet disturbed soils, sometimes emergent.
Elevation: 0–300 m.
Distribution
Introduced; Ala., Ark., Fla., Ga., La., Miss., Mo., N.C., Okla., S.C., Tex., Asia, Africa, introduced also in Mexico, West Indies, Central America, South America.
Discussion
Sphenoclea zeylanica is a common weed of rice fields and other wet disturbed sites in the coastal prairies of southern Louisiana and southeastern Texas. It occurs sporadically in other southeastern states, and its dispersal is correlated with rice agriculture. The earliest records in the United States were collected in Louisiana about 1850, where it was probably introduced as a contaminant of rice seed (J. R. Carter et al. 2014).
West African plants with shorter oblong spikes, pink corollas, and stamens with longer filaments are sometimes segregated as the endemic Sphenoclea dalzielii N. E. Brown (S. M. H. Jafri, http://www.tropicos.org/Name/ 5504127).
Selected References
None.