Medium to tall erect plant. Stems zig-zagged, leaves oblong, round at base, long stalked (as long as leaf blade); the upper leaves narrower and pointed. The flowers in rather distant clusters, forming a much branched panicle. Flowering branches leafy, almost to the top. Fruit valves oval, untoothed all swollen.

all 3 tubercles well-developed, tubercles oblong and smooth

The fruits have a central part, triangular in cross-section, with three membraneous valves surrounding a small, hard 'tubercle'.  The shape and arrangement of valves and tubercles is diagnostic, and close-up photos of fruits and leaves/general habit is needed.

Damp grassy habitats, marshy meadows, ditches and stream banks.

June to October.

Perennial.

Found throughout Britain, but more local in the north and in Wales

Common in Leicestershire and Rutland. In the 1979 Flora survey of Leicestershire it was found in 384 of the 617 tetrads.

In the current Checklist (Jeeves, 2011) it is listed as Native, Frequent

http://www.kenadams.org.uk/esb/Docks.htm