Description from Flora of China
Oenothera octovalvis Jacquin, Enum. Syst. Pl. 19. 1760; Jussiaea angustifolia Lamarck; J. octonervia Lamarck; J. octonervia f. sessiliflora Micheli; J. octovalvis (Jacquin) Swartz; J. pubescens Linnaeus; J. suffruticosa Linnaeus; J. suffruticosa f. angustifolia (Lamarck) Alston; J. suffruticosa var. subglabra Thwaites ex Trimen; J. suffruticosa f. villosa (Lamarck) Alston; J. villosa Lamarck; Ludwigia octovalvis subsp. sessiliflora (Micheli) P. H. Raven; L. pubescens (Linnaeus) H. Hara.
Herbs robust, erect, perennial, sometimes woody at base or even shrubby. Stems 25-400 cm tall, well-branched, densely spreading pubescent at least on upper stem, or puberulous or subglabrous. Petiole 1-10 mm; leaf blade linear to subovate, 1-14 × 0.3-4 cm, lateral veins 11-20 per side, submarginal vein prominent, base narrowly or broadly cuneate, apex attenuate. Sepals 4, ovate or lanceolate, 6-15 mm. Petals yellow, broadly obovate, 6-17 × 5-17 mm. Stamens 8; filaments 1-4 mm; anthers 1.2-4 mm; pollen in tetrads. Style 1.5-3.5 mm; stigma subglobose, shallowly 4-lobed. Capsule pale brown with 8 darker ribs, cylindric, terete, 1.7-4.5 cm, 2-8 mm in diam., thinly walled, readily and irregularly loculicidal; pedicel 1-10 mm. Seeds in 2 or more rows per locule, free, brown, 0.6-0.75 mm, raphe inflated and equal in size to seed body, evenly transversely ridged. Fl. and fr. Jan-Dec. 2n = 32, 48*.
The pattern of variation in this cosmopolitan species is extremely complex and needs further careful analysis; in the absence of a more definitive treatment, we have abandoned the subspecies recognized by Raven (Reinwardtia 6: 327-427. 1963). The three other species recog nized in Ludwigia sect. Macrocarpon (Micheli) H. Hara occur only in the Neotropics, as do most species in the presumably related L. sect. Myrtocarpus (Munz) H. Hara, which suggests that this widespread species may have arisen there and spread worldwide, presumably assisted by human activities.
Moist to wet places along streams, ponds, or lakes, often on disturbed and/or cultivated sites, common and widespread; near sea level to 2200 m. Fujian, Guangdong, Guangxi, Guizhou, Hainan, Jiangxi, Sichuan, Taiwan, E Xizang, Yunnan, Zhejiang [India, Japan, Malaysia, Myanmar, Singapore, Thailand, Vietnam; widespread throughout Africa, S, SE, and SW Asia, Australia, Europe, North America, Pacific islands, South America].