Arrowhead
From Cookipedia
Sagittaria or "arrowhead" is a genus of about 20 species of aquatic plants whose members go by a variety of common names, including arrowhead, duck potato,iz-ze-kn, katniss, kuwai, swan potato, tule potato, and wapatoo.
Several species bear tubers edible as a starchy root vegetable that are collected from the wild or cultivated as crops in North America and East Asia.
See also
There is a very comprehensive list of corms and tubers here