Description from Flora of China
Plants 10–80 cm. Roots fibrous. Stems decumbent. Basal petioles 5–10 cm; blade oblong-ovate, 1–2-pinnate; ultimate segments ovate or rhombic-ovate, 5–50 × 5–20 mm, margins serrate. Cauline leaves gradually reduced upwards, smaller, becoming sessile on expanded sheaths. Umbels 3–5 cm across; peduncles 2–16 cm; bracts absent, or occasionally 1, linear, 3–11 mm; rays 6–16(–30), 1–3 cm, subequal or unequal; bracteoles 2–8, linear, 2–4 cm, as long as pedicels; umbellules ca. 20-flowered; pedicels 1.5–4 mm. Calyx teeth ca. 0.5 mm. Styles patent, 1.2–2 mm. Fruit subglobose or ovoid, ca. 2.5 × 2 mm; dorsal and intermediate ribs slightly corky-thickened.
The complex nomenclatural history reflects the taxonomic problems with these morphologically very variable, widespread plants. Leaf morphology is particularly variable, and the size and shape of the leaves of the subsp. javanica converge with subsp. rosthornii in Malaysia and adjoining areas. Outside China, some authors have a broader species concept for Oenanthe javanica, including O. benghalensis and O. linearis within it. Further work over a wide geographic area is needed to resolve the classification.
Grassland at forest margins, marshlands, water meadows, lakeshores, river banks, muddy stream banks, shallow water; 600–4000 m. Throughout China [India, Indonesia, Japan, Korea, Laos, Malaysia, Myanmar, Nepal, New Guinea, Pakistan, Philippines, Russia, Thailand, Vietnam].