Medium to tall to 2.5 metres. Hairless. Stems erect, hollow, purple-brown spotted with a whitish bloom. Leaves finely cut. Flowers white 2 mm in umbels with 10 to 20 rays, sepals absent, bracts present.

Other tall white umbellifers with ferny leaves

Tall, hollow stem, usually purple-spotted; 2-4 pinnate leaves; bracts and bracteoles; rounded strongly-ridged fruits. 

Damp habitats, ditches, banks, roadside verges, waterside locations.

June and July.

Annual or biennial.

Frequent throughout much of Britain, less so in Scotland.

It is quite frequent in Leicestershire and Rutland. In the 1979 Flora survey of Leicestershire it was found in 258 of the 617 tetrads.

In the current checklist (Jeeves 2011) it is listed as Alien (archaeophyte); locally frequent)