2. Ludwigia perennis Linnaeus, Sp. Pl. 1: 119. 1753.
细花丁香蓼 xi hua ding xiang liao
Jussiaea caryophyllea Lamarck; J. perennis (Linnaeus) Brenan; Ludwigia caryophyllea (Lamarck) Merrill & F. P. Metcalf; L. parviflora Roxburgh.
Herbs erect, annual, with taproot. Stems 20-100 cm tall, branched, subglabrous or minutely puberulous on younger parts. Petiole 2-15 mm, winged; leaf blade narrowly elliptic to lanceolate, 1-11 × 0.3-2.7 cm, lateral veins 6-12 per side, submarginal vein inconspicuous, base narrowly cuneate, apex subacute. Sepals 4, rarely 5, deltate, (1.3-)2-3.5 mm, glabrous or minutely puberulous. Petals yellow, elliptic, 1-3 × 0.7-2 mm. Stamens as many as sepals, or rarely more; filaments 0.3-0.7 mm; anthers 0.5-0.7 mm; pollen in tetrads. Style 0.7-1.5 mm; stigma globose. Capsule often nodding, pale brown, oblanceoloid, terete, 3-16(-19) mm, 2.5-5 mm in diam., thinly walled, readily and irregularly loculicidal, glabrous or puberulous, sessile or pedicel to 6 mm. Seeds in 2 or more rows per locule, free, brown with fine brown lines, 0.3-0.5 mm, raphe very narrow and inconspicuous. Fl. and fr. Jul-Nov. 2n = 16.
Wet sites such as flood plains, roadside ditches, muddy wallows, abandoned rice paddies; near sea level to 1200 m. Fujian, Guangdong, Guangxi, Hainan, Jiangxi, Taiwan, Yunnan [Bangladesh, Bhutan, India, Indonesia, Japan, Myanmar, Nepal, Philippines, Sri Lanka; Africa (including Madagascar), SE and SW Asia, Australia, Pacific islands (New Caledonia)].