Herbs, perennial, not stranded by low tide. Leaves submersed and emersed; submersed leaves sessile, blade linear; emersed petiolate, blade hastate to sagittate. Inflorescences of 1--15 whorls, floating or emersed; bracts connate. Flowers: pistillate without ring of sterile stamens; petals with purple spot at base.

Flowering summer--fall (Jul--Oct). Wet ditches, mud flats of rivers; 0--10 m; introduced; Ala., Fla., Ga.; c, s South America.

Sagittaria montevidensis subsp. montevidensis apparently is native to South America. It has been introduced along the coast of the Gulf of Mexico.