Hemicryptophyte (biennial). To 120(–150) cm; often with a foetid odour, at least when scratched (rarely odourless); tap­root 5–11(–17) mm thick. Stem straight, hollow or rarely solid, branched mainly in the upper part, with the primary umbel situated at the top; basal part 4–8(–10) mm thick, terete or angled, usually with purplish, sometimes confluent spots, usually distinctly glaucous; upper internodes usually sulcate. Leaves 5–15 at the base (usually withered at anthesis) and 9–16 on the stem; sheath rather broad, sometimes purplish, on the upper leaves having a distinctly membranous border with rounded tips; petiole 7–16 cm; blade 2–3(–4)-pinnate, 7–27(–33) × 8–23 cm (length/width ratio 1–1.6), lower side ± glaucous. Primary leaflets 5–7 pairs; angle leaflet/rachis 40–60°; longest petiolules 6–36(–60) mm. Ultimate leaflets 2(–3)-pinnatifid, with (5–)7–9 pairs of lobes/teeth; petiolule 2–12 mm; blade 8–34(–43) × 6–26(–39) mm (length/width ratio 1–1.8); base shortly attenuate to truncate. Ultimate lobes (0.7–)1–3.4 × 0.6–2.5 mm, with a length/width ratio of 0.8–1.7(–2.2); apex acute to acuminate (rarely mucronate), with a white tip.

Distribution. Nem–BNem(–SBor). – Probably archaeophytic in the southern parts of the distribution area. Earlier grown for medicinal purposes; also, even recently, brought in and spread with grain. – D common on the eastern islands (though rare in Brn) and northern ØJy, scattered in the rest of Jylland. N casual from Øf Halden north to He Hamar, and along the coast to VA, Ho Bergen and Granvin, ST Skaun and Trondheim; NNo Bodø. S as an archaeophyte scattered in the lowlands north to BhG, Vg, southern and eastern Vsm and Upl; less common in the southern uplands (northern Sk and Bl, eastern Hl, SmI and southern Vg); further north rare, mainly casual and probably a fairly recent introduction: southeastern Dls, southern and central Vrm (perhaps resident in the southernmost part), southeastern Dlr (probably resident in Falun), coastal Gst, Hls Söderala 1981–90 (throwout), Söderhamn 19th century (ballast), Mpd Alnö, Skön, Sundsvall and Timrå (all before 1910; ballast); Jmt Undersåker (Järpen 1911, railway station), Nb Piteå 2003 (refuse tip); strongly declining in the 20th century except on seashores at the western coast where it has increased slightly. F scattered to fairly rare north to southern St, southern EH, and the whole of PS; rarer and mostly casual further north to KP Raahe and Rantsila, Kn Hyrynsalmi and Kajaani and OP Oulu.

Habitat. Moderately dry, mull-rich, nutrient-enriched bare soil in light-open habitats; mainly on strongly disturbed ground such as farms, pastures, roadsides and ruderal places. Probably continually brought in with cereals, ley seed and ballast until the middle of the 20th century, formerly found as a field weed (at least in S Srm, Upl and Vsm), at loading places and mills. Also, but probably secondarily, on seashores, especially on seaweed drift, at least in D and S (west coast and Öl).

Biology. All flowers are bisexual, or outer flowers in umbellules of primary and secondary umbels female. The whole plant contains the extremely poisonous and volatile alkaloid coniine.

Similar taxa. The tall unbranched pruinose stem with red spots is characteristic for Conium maculatum. There are some Chaerophyllum species with tall, spotted stems but their stems are usually bristly at least at the base, they have no bracts and the fruits are elongated with low ridges. Anthriscus sylvestris is lower, has unspotted, more zigzag-shaped stems and there are no bracts. Aethusa cynapium has unspotted stems, narrower leaf-lobes and bractlets, and no bracts.