Sagittaria is a genus of about 30 species of aquatic plants whose members go by a variety of common names, including arrowhead, duck potato, iz-ze-kn,katniss, kuwai (慈姑 in Japanese), swan potato, tule potato, and wapato (or wapatoo). Most are native to South, Central, and North America, but there are also some from Europe, Africa, and Asia.
Sagittaria plant stock (the perennial rhizome) is a horizontal creeper (stoloniferous) and obliquely obovate, the margins winged, with apical or ventral beak; in other words, they are a small, dry, one-seeded fruit that do not open to release the seed, set on a slant, narrower at the base, with winged edges, and having a "beaked" aperture (one side longer than the other) for sprouting, set above or below the fruit body.
One of the names for this plant is derived from the edible underwater tuber that the plant produces. In late fall or early spring, disturbing the aquatic mud in which the plant grows will cause its small tubers to float to the surface where they can be harvested, and then boiled.
Sagittaria kurziana Glück – Springtape or Strap-leaf Sagittaria - Florida; naturalized in Mariana Islands
Sagittaria lancifoliaL. – Bulltongue Arrowhead - southeastern USA from Texas to Delaware; West Indies; Latin America from southern Mexico to Brazil
Sagittaria latifolia Willd. – Duck-potato, Broad-leaved Arrowhead, Wapato - widespread across most of North America, the West Indies and northern South America; naturalized in Hawaii, the western Himalayas and parts of Europe
Sagittaria lichuanensis J.K.Chen, X.Z.Sun & H.Q.Wang - southern China
Sagittaria longiloba Engelm. ex J.G. Sm. – Longbarb Arrowhead - southern Great Plains, Arizona, New Mexico, California, Mexico, Nicaragua, Venezuela
Sagittaria × lunata C.D.Preston & Uotila - Sweden, Finland, northern Russia (S. natans × S. sagittifolia)
Sagittaria platyphylla (Engelm.) J.G.Sm. – Delta Arrowhead, Delta Duck-potato - south-central USA with scattered populations in southeast, the Ohio Valley and Washington State; also Mexico and Panama; naturalized in South Australia, Italy, Java, Caucasus
Sagittaria rhombifolia Cham. - Costa Rica; widespread across much of South America
Sagittaria rigida Pursh. – Canadian Arrowhead - Canada from Quebec to Saskatchewan; common in northeastern and north-central USA from Arkansas and Nebraska east to Virginia and New England; scattered populations in California, Idaho and Washington State; naturalised in Great Britain
Sagittaria trifolia L. – Threeleaf Arrowhead - widespread across much of Asia including Siberia, China, Japan, India, Iran, Indonesia, Philippines, etc.; also Ukraine and European Russia; naturalized in Fiji and Polynesia