A stiff, erect plant with a creeping, far reaching rhizome. Leaves in close whorls of 6 to 12, linear lanceolate, pointed and untoothed. Flowers are tiny, greenish with reddish anthers, borne in the axils of the upper leaves.

In shallow water of lakes, ponds and canals plus various other wet places.

Flowers June and July.

Perennial.

Widespread and fairly frequent in Britain, though less so in the west.

Infrequent in Leicestershire and Rutland. In The Flora of Leicestershire (Primavesi & Evans) it was found in 10 of the 617 tetrads.

It was on the 2011 VC55 Rare Plant Register (Jeeves, 2011) but is not on the current RPR (Hall & Woodward, 2022); it is listed as 'data deficient' because it is not clear whether records are of introduced/escaped plants or natives.