Monochoria vaginalis is a species of flowering plant in the family Pontederiaceae (water hyacinth family). It's known by a munber of common names, including lesser water hyacinth, heartleaf false pickerelweed and oval-leafed pondweed. It is an invasive aquatic plant, that grows in rice paddies and other water bodies. This is an annual or perennial herb growing in water from a small rhizome. The shiny green leaves are up to about 12 centimeters long and 10 wide and are borne on rigid, hollow petioles. The inflorescence bears 3 to 25 flowers which open underwater and all around the same time. Each has six purple-blue tepals just over a centimeter long. The fruit is a capsule about a centimeter long which contains many tiny winged seeds.