Apium cicutifolium (Schrenk) Bentham & Hooker ex Forbes & Hemsley; Cicuta dahurica Fischer ex Schultz; Sium cicutifolium Schrenk; S. formosanum Hayata; S. nipponicum Maximowicz.

Plants 60–120 cm, stout. Root fibrous or fascicled, fusiform. Leaf blade oblong or ovate, 6–25 × 7–10 cm; pinnae 3–9 pairs; leaflets lanceolate or linear, 10–40 × 3–15 mm, margin serrate. Upper leaves smaller, 3-lobed or entire, sessile on expanded sheaths. Umbels 4–8 cm across, terminal on stem and branches; bracts 6–10, lanceolate or linear-lanceolate, 3–15 mm, entire or incised; rays (8–)10–20, 1.5–3 cm, unequal; bracteoles 5–10, linear-lanceolate, 1–3 mm, entire; umbellules 10–20-flowered; pedicels 3–5 mm. Calyx teeth triangular-lanceolate or minute triangular, 0.5–2 mm. Fruit ovoid, ca. 3 × 2 mm, ribs prominent, corky, thickened, narrowly winged; vittae 1–3 in each furrow, 2–6 on commissure. Fl. Jul–Aug, fr. Sep–Oct.

This species has reputed medicinal value. Sium ninsi Thunberg (Fl. Jap. 118. 1784), known from Korea, Japan, and SE Russia, is likely to occur also in SE Heilongjiang and E Jilin. The upper part of the plant is morphologically similar to S. suave but can be distinguished by the long-petiolate, ternate uppermost cauline leaves (vs. sessile in S. suave).

Damp grasslands, marshlands, streamsides. Hebei, Heilongjiang, Jilin, Liaoning, Nei Mongol, Ningxia, Shandong, Taiwan [Japan, Korea, Russia; North America].