Alisma

Erect aquatic perennial herb to 1 m high. Leaves variable, submerged leaves strap-like; emergent leaves with up to 7 prominent parallel veins and on a stalk to 80 cm long that is flat on one side and with small wings at the base. Aggregate fruit triangular in outline, individual 1-seeded fruit 2–2.5 mm long and falling singly.