Conium maculatum L.
Robust biennial herb, 1–2.5 m high, stems hollow, spotted reddish brown or purple.
Leaves acrid-smelling when crushed, triangular in outline, 30–50 cm long,2–4-pinnate; segments 1–2 cm long, margins coarsely toothed, glabrous; petiole to 60 cm long, longitudinally furrowed, purple-flecked, with a broad sheathing base.
Umbels 3–7 cm diam.; peduncle to 20 cm long; rays 6–20, 1.5–3.5 cm long; bracts 5–6, 2–8 mm long, reflexed; umbellules 5–8 mm diam.; pedicels 10–15, 2–5 mm long; bracteoles 3–6, ovate, 2–2.5 mm long, acuminate, often fused towards base. Petals c. 1.2 mm long, white.
Fruit ovoid to globose, 2.5–4 mm long; mericarps with 5 prominent undulate-crenate ribs.