Hydrilla reproduces by stem fragmentation and by forming tubers beneath the hydrosoil and turions at the leaf axils. The plant closely resembles another invasive exotic, Brazilian Elodea, and two native species of American Elodea. Creeping waterprimrose is a perennial native to Central or South America that grows to 3 feet tall. Stems may be much longer when floating on the water, forming large free-floating mats. It may grow terrestrially and form a woody reddish-brown stem.
Leaves are alternate and vary in shape from rounded in early growth to pointed in the mature stage.
Stems are often covered with hairs. Waterprimrose reproduces by fragmentation and seed. Purple loosestrife, a beautiful but aggressive invader, arrived in eastern North America in the early 1800's. It is a very hardy perennial which can rapidly degrade wetlands. Purple loosestrife grows to 6 feet with multiple woody stalks.