Potamogeton polygonifolius L. or Bog Pondweed, is an aquatic species in the genus Potamogeton

Potamogeton

Potamogeton is a genus of aquatic, mostly freshwater, plants of the family Potamogetonaceae. Most are known by the common name pondweed, although many unrelated plants may be called pondweed, such as Canadian pondweed...

. It is found in shallow peaty acid water and bog pools.

Description

This species is very variable but often closely resembles Broad Leaved pondweed Potamogeton natans

Potamogeton natans

Potamogeton natans L. is an aquatic species in the genus Potamogeton native to quiet or slow-flowing freshwater habitats throughout the Holarctic Kingdom....

 in its habitat and shape of leaves.

However in contrast it has submerged as well as floating leaves. All the leaves are stalked, leathery, lanceolate to oval shaped, 4 to 10 cm long. they are either tapered into a stalk or cordate at the base. It does not have the buff coloured flexible joint at the top of the stalk. The longitudinal veins are darker.

The flower spikes are smaller but still dense than Potamogeton natans

Potamogeton natans

Potamogeton natans L. is an aquatic species in the genus Potamogeton native to quiet or slow-flowing freshwater habitats throughout the Holarctic Kingdom....

. It has 4 perianth

Perianth

The term perianth has two similar but separate meanings in botany:* In flowering plants, the perianth are the outer, sterile whorls of a flower...

 segments. It flowers from May to October. The stipules are 1 to 5 cm, and 2 ridged.

The fruits are 2 mm wide and long, reddish with a tiny beak.