Sium medium Fisch. & C. A. Mey.

Plants 30–60(–80) cm. Roots fibrous. Basal petioles 6–15 cm; blade oblong-ovate, 12–20 × 5–13 cm; pinnae 3–5 pairs; leaflets oblong-lanceolate, 2.5–6 × 0.5–1 cm, margins serrate. Upper leaves similar to basal, smaller, sessile, pinnae 2 pairs on expanded sheaths. Umbels 3.5–5 cm across; peduncles 7–10 cm; bracts 8–9, linear or lanceolate, 5–13 mm, entire; rays 15–23, 0.8–19 mm, unequal; bracteoles 9–10, linear, 3–4.5 mm, shorter than pedicels, entire; umbellules 8–20-flowered; pedicels 2–5 mm. Calyx teeth minute, triangular, ca. 0.2 mm. Fruit ellipsoid, ca. 3.2 × 2 mm; ribs filiform, thinly corky; vittae 1–2 in each furrow, 2–6 on commissure. Fl. Jul–Aug, fr. Sep–Oct.

Marshlands, lake margins, streamsides. Xinjiang [Kazakhstan, Kyrgyzstan, Tajikistan, Uzbekistan].