The perennial is 20-80 cm tall, with the floating shape reaching up to 120 cm in length. The triquetrous leaves are 5-10 mm broad. The inflorescence is built of spherical flower heads of 1.5-3 cm across – with the staminate above, and pistillate below.
It is a common species of lakeshores, back-waters and swamped bayous. In contrast to shoals, in deeper spots it grows floating leaves. It flowers June to August.
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