Gooseweed, chickenspike

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.

Flowering Jun–Nov. Rice fields, ditches, shallow margins of ponds and lakes, stream banks, wet disturbed soils, sometimes emergent; 0–300 m; 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.

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).