water mint (M. aquatica), Hart's pennyroyal (M. cervina)
Could be confused with
Species commonly cultivated
Mentha aquatica L. (Africa, Asia, Europe)
M. cervina L. (northern Africa, Europe)
The commonly grown economically important mint species have a worldwide distribution.
Mentha pulegium L., a non-aquatic species, is sometimes weedy.
erect or ascending, creeping stem plant
Aromatic perennial, stoloniferous or rhizomatous. Stems creeping, erect or ascending. Leaves opposite; leaf blade entire or serrate (some cultivars wavy). Inflorescence a terminal or axillary spike or cluster. Sepals 5, subequal, fused below; petals fused below into a tube, lobes 4, equal, or adaxial lobe (lip) larger and emarginate and the flower zygomorphic, pink or white. Dispersal vegetative and of fruit (nutlet) sometimes by water.
Mentha is widely known for its culinary and other economic uses. The genus consists of nineteen "pure" species, but more than 2000 botanical names cover many different growth forms and cultivars. Mentha aquatica is usually the name given to the plant(s) most commonly offered for sale or grown in the pond garden trade. In some cases, these plants may also be known by a hybrid and/or cultivar name.