Growing in slow-moving fresh water, this erect, robust plant flowers from July to early September. The stiff, upright stems are branched in the upper parts and can grow to 1 metre in height. The bright-green leaves are keeled and strap-shaped. The spherical flower-heads are in terminal panicles, the lower, green flowers being female and the upper, yellowish with black tips, being male. The fruits are in spherical heads. This is a native plant and belongs to the family Sparganiaceae.
I first identified this plant in Lough Derg, Co Tipperary in 1981 and photographed it at Saltmills, Co Wexford in 2009.
If you are satisfied you have correctly identified this plant, please submit your sighting to the National Biodiversity Data Centre