arrowhead (or arrowleaf) Sagittaria sagittifolia, a perennial water or marsh plant of Europe, Asia, and America, is named for the shape of its leaves, but it is the starchy, tuberous roots which are usually eaten and for which the plant is cultivated in Asia.
A distinction was formerly made between S. sagittifolia and what were regarded as two other species: S. sinensis of China and Japan, and S. latifolia of N. America. However, all are now classified as a single species.
In N. America arrowhead has long been gathered from the wild by Indians (for whom it was probably the most valuable of the available root crops) and sometimes by white inhabitants. This has the Chinook name ‘wappatoo’, now rendered as ‘wapato’, meaning potato; and is also called ‘duck potato’ because water birds are fond of the leaves.