Potamogeton polygonifolius can be distinguished from the commonest UK pondweed species, potamogeton natans, by its leaf veins, which are dark and opaque rather than light brown and translucent.
Main flower color:
Most of the British Isles; least common in southeast England
A few cm
Bogs and ponds on heaths and moors; acidic soils
Tiny, with four petal-like segments and four stamens, arranged in a short, dense, vertical spike
Alternate, shiny, ovate, leathery, crossed by darker, parallel veins. Up to 10 cm long and 4 cm wide. Usually has both floating (upper) leaves and submerged (lower) leaves, these latter similar in size but more lanceolate in shape, and translucent
May to October