Alligator Weed

Alternanthera philoxerioides is said to reproduce only vegetatively in North America. I have seen no fruit or seed.

Herbs, perennial, aquatic to semiterrestrial, stoloniferous, to 50 dm. Stems prostrate, forming mats, often fistulose, glabrous. Leaves sessile; blade narrowly elliptic, elliptic, or oblanceolate, 3.5-7.1 × 0.5-2 cm, herbaceous, apex acute to obtuse, glabrous. Inflorescences terminal and axillary, pedunculate; heads white, globose, 1.4-1.7 cm diam.; bracts not keeled, less than ¹/2 as long as tepals. Flowers: tepals monomorphic, white, lanceolate or oblong, 6 mm, apex acute, glabrous; stamens 5; pseudostaminodes ligulate. Utricles not seen. Seeds not seen.

Herbs perennial. Stem ascending from a creeping base, 55-120 cm, branched; young stem and leaf axil white hairy; old ones glabrous. Petiole 3-10 mm, glabrous or slightly hairy; leaf blade oblong, oblong-obovate, or ovate-lanceolate, 2.5-5 × 0.7-2 cm, glabrous or ciliate, adaxially muricate, base attenuate, margin entire, apex acute or obtuse, with a mucro. Heads with a peduncle, solitary at leaf axil, globose, 0.8-1.5 cm in diam. Bracts and bracteoles white, 1-veined, apex acuminate; bracts ovate, 2-2.5 mm; bracteoles lanceolate, ca. 2 mm. Tepals white, shiny, oblong, 5-6 mm, glabrous, apex acute. Filaments 2.5-3 mm, connate into a cup at base; pseudostaminodes oblong-linear, ca. as long as stamens. Ovary obovoid, compressed, with short stalk. Fruit not known. Fl. May-Oct. 2n = 100*.

E Nepal: Native of Brazil, introduced in many tropical countries.

introduced; Ala., Ark., Calif., Fla., Ga., Ill., Ky., La., Miss., N.C., S.C., Tenn., Tex., Va.; West Indies; native to South America.

100-200 m

Flowering early spring-summer.

Herbs

Ponds, ditches, streams, bayous; 0-200m.

Cultivated, waste places. Beijing, Fujian, Guangxi, Hebei, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Taiwan, Zhejiang [native to South America (Brazil)].

Bucholzia philoxeroides Martius, Beitr. Amarantac., 107. 1825; Achyranthes philoxeroides (Martius) Standley

Bucholzia philoxeroides C. Martius, Nov. Actorum Acad. Caes. Leop.-Carol. Nat. Cur. 13(1): 107. 1825; Achyranthes philoxeroides (C. Martius) Standley; Telanthera philoxeroides (C. Martius) Moquin-Tandon.