Erect stems to 150 cm high and 2 to 10 mm thick, either unbranched or with whorls of simple branches. Stems have 10 to 30 very fine shallow grooves and a large central cavity, three quarters of the diameter of the stem or more. Stems have numerous tight, green often orange tinged sheaths that bear short, dark, triangular pale edged teeth. Terminal cones are 1 to 1.5 cm long.

In slow moving freshwater, and pond and lake margins.

June and July

Perennial

Fairly common throughout Britain.

Fairly frequent in Leicestershire and Rutland. In the 1979 Flora survey of Leicestershire it was found in 107 of the 617 tetrads.