Elodea, a small herb that grows beneath the surfaces of freshwater ponds and rivers. Also known as waterweed and ditch moss, elodea is native to North America, but was introduced into Europe where it is considered a pest. The delicate white flowers are arranged along a pistil, or tube, that floats on water. The small, oblong fruits are eaten by wild ducks. Elodea leaves are used in biology classes to demonstrate the nature of protoplasm and to study cell structure. Elodea is a popular aquarium plant.

Elodea is Elodea canadensis of the family Hydrocharitaceae.