Potamogeton perfoliatus L.
Plant length 0.3m-3m long.
A submerged perennial pondweed which grows from a network of rhizomes. The leaves are alternatively arranged and perfoliate (having no stalks but growing from the stem). The leaves are broad and oval with wavy margins, and fairly pale. The flowers are small and greenish, and on spikes which grow above or below the water.
It is seen June to September, in rivers, canals and reservoirs. Common and widespread throughout Britain.