Potamogeton natans, commonly known as broad-leaved pondweed, floating pondweed, or floating-leaf pondweed, is an aquatic species in the genus Potamogeton native to quiet or slow-flowing freshwater habitats throughout the Holarctic Kingdom.
Description
It produces both floating and submersed leaves on the same plant. The floating leaves are ovate to oblong-ovate and almost always cordate at the base. They are dark green, leathery, opaque, with translucent longitudinal veins. They are 5 to 10 cm long, pointed at the tips, and rounded at the base.
The stipules are 4 to 17 cm long.
The submerged grass-like structures are called phyllodes, are actually modified leaf stalks.
The stems are cylindrical, without many branches, and grow from 1 to 2 metres.
The main difference between this species and other pondweeds is a discoloured flexible joint just below the top of the long leaf stalk.
The flower spikes are dense, and cylindrical. They are 5 to 10 cm long, pointed at the tip and rounded at the base. It flowers from May to September.
The fruits are 4 to 5 mm long and obovate.