Description from Flora of China
Ammannia rosea Poiret, Encycl., Suppl. 1: 329. 1810; A. leptopetala Blume; A. littorea Miquel; A. pentandra Roxburgh; Rotala leptopetala (Blume) Koehne; R. littorea (Miquel) Nakai; R. pentandra (Roxburgh) Blatter & Hallberg.
Herbs, annual, terrestrial or amphibious, 8-30 cm. Stems ascending or erect, mostly unbranched. Leaves decussate, linear-lanceolate to lanceolate-oblong, 7-30 × 3-5 mm, base obtuse [to cuneate], apex obtuse to retuse. Bracts similar to foliage leaves, longer than flowers. Flowers 5-merous, solitary, sessile, axillary on main stem and branches; bracteoles linear, slightly shorter than floral tube. Floral tube campanulate, 1-1.5 mm; sepals (4 or)5, very short, ca. 0.25 mm, apex acuminate; epicalyx segments setiform, equaling sepals. Petals (absent to)5, ca. 0.25 mm, not persistent. Stamens 5; anthers reaching margin of floral tube. Ovary globose; shorter than ovary. Capsules globose, ca. 2 mm in diam., well exserted from floral tube, apex red, 3-valved. Seeds ca. 0.3 mm. Fl. and fr. Aug-Oct in temperate regions, throughout year in tropical regions.
Paddy fields, wet places; lowlands. Fujian, Guangxi, Guizhou, Hainan, Jiangsu, Yunnan; naturalized in Taiwan (Nantou) [Bangladesh, Indonesia, Myanmar, Malaysia, Philippines, Thailand, Vietnam].