Alisma is a genus of flowering aquatic herbs, commonly called water plantains. They are perennial plants with white, pink, or purple branching flowers and broad leaves, though the leaves may be ribbon-like if submerged. Alisma plants are found nearly worldwide in diverse habitats, including flooded or saturated soil, marshes, swamps, and shallow water. They generally bloom from late spring to summer.
Water plantains are called Copóg Phádraig, meaning "leaf of Patrick," in Ireland, after the country's patron saint, and folklore holds that they ward against fairies. In the 19th century, English art critic John Ruskin hailed the curve of the plant's leaf ribs as an example of "divine proportion" that architecture and art should take as a model. The name Alisma may be derived from a Celtic word meaning "water."
Alisma gramineum, commonly called grass-leaved water plantain, narrowleaf water plantain, or ribbon-leaf water plantain, grows in parts of North America, Europe, and North Africa. It grows in mud or shallow water, and features purplish-white flowers that may or may not be submerged. If submerged, the flowers remain closed and self-pollinate. Similarly, the leaves are stiff if they grow above the water, but ribbon-like if submerged.
Also called the lanceleaf water plantain, Alisma lanceolatum is native to parts of Asia, Europe, and North Africa. It has become an invasive species in some environments to which it has been introduced, including parts of North America. A. lanceolatum can grow in mud or fresh water. It has small, pink flowers that open in the morning and bloom during the summer months.
Alisma plantago-aquatica, also called common water plantain or mad-dog weed, is native throughout the Northern Hemisphere. It also grows in fresh water or mud, and features flowers with three white or purple petals. The dried flowers have diuretic and diaphoretic properties, meaning they induce urination and perspiration. The plant has been used to treat such ailments as dysentery, epilepsy, kidney stones, and rabies. In Traditional Chinese Medicine (TCM), the plant is used to treat a range of genital and urinary system disorders, as well as excess phlegm, abdominal bloating, and diabetes.
American water plantain, Alisma subcordatum, is native to the eastern half of the United States. It has three-petaled pink flowers and grows in the mud in a variety of wet environments. Alisma triviale, also called northern water plantain, is native to northern Mexico, the United States, and Canada.