8. Ludwigia ×taiwanensis C. I Peng, Bot. Bull. Acad. Sin. 31: 344. 1990.
台湾水龙 tai wan shui long
Herbs perennial, with creeping or floating stems rooting at nodes, sometimes with white, erect, spindle-shaped pneumatophores in clusters at nodes of floating stems. Floating stems to 100 cm, terrestrial stems 20-60 cm, branched, ascending, glabrous. Petiole 5-30 mm; leaf blade narrowly elliptic to spatulate-oblong, 0.7-9.5 × 0.4-2.7 cm, glabrous, submarginal vein inconspicuous, base narrowly cuneate or attenuate, margin entire, apex rounded or obtuse. Sepals 5, narrowly triangular-lanceolate, 8-12 mm, glabrous to hirtellous. Petals pale yellow, broadly obovate, 1.3-1.8 cm × 9-12 mm. Stamens 10; filaments 2-3.5 mm; anthers shriveled, indehiscent; pollen in monads, abortive. Style 5-7 mm; stigma discoid; pedicels 1.5-6 cm. Capsules not maturing, falling soon after flowering. Seeds absent (sterile). Fl. May-Dec, fr. absent. 2n = 24*.
● Wet disturbed areas in drainage ditches, fallow and wet paddies, along river banks, swampy waste grounds, borders of ponds or reservoirs; near sea level to 500 m. Fujian, Guangdong, Guangxi, Hainan, Hunan, Jiangxi, Sichuan, Taiwan, Yunnan.
This is the hybrid Ludwigia adscendens × L. peploides subsp. stipulacea.
These triploid (2n = 24) populations of natural hybrids between Ludwigia adscendens (n = 16) and L. peploides subsp. stipulacea (n = 8) are widespread in S China (Peng, Bot. Bull. Acad. Sin. 31: 343-349. 1990; Gu et al., Cathaya 3: 37-44. 1991). Plants of this complex are very plastic vegetatively and are best distinguished by reproductive features. The color of the petals is bright yellow in L. peploides subsp. stipulacea, white with a yellow base in L. adscendens, and pale yellow in the hybrid. Ludwigia ×taiwanensis, which in the past was usually misidentified as L. peploides subsp. stipulacea, flowers profusely, but the ovary aborts and never matures as a ripe fruit. Although L. ×taiwanensis is highly sterile, it readily regenerates and establishes large colonies from fragments.