Duck potato (Sagittaria latifolia) is an aquatic emergent, meaning it typically grows in shallow water, with the leaves rising above. It grows vegetatively, creating dense colonies, which is great in its natural habitats. Unfortunately it has become invasive outside of North America where it was spread as an ornamental.
I could find information on only a single species of caterpillar that uses it as a host plant, the catocaline dart. However, as the name implies, the roots are beneficial to waterfowl, especially ducks, which can pull them up and eat them. The plants also provide a complex habitat for aquatic organisms that open water lacks.
As with ducks, the main edible part of this plant for humans is the root, which can be eaten raw or cooked. It has a similar taste to potatoes or chestnuts and can be cooked in similar manners. It can also be dried and powdered into a kind of flour. The young unfurling leaves and stalk can also be boiled and eaten. The flower stalks before the blossom are also tender and good when boiled. The petals of the blossoms are edible raw, and the lateral tips of the rhizomes are edible raw or cooked.
This plant can be confused with Arrow arum, which is poisonous, so do not eat unless you know for sure, and you shouldn’t be harvesting in the wild anyways. The arum leaf apparently is distinct in that it is veinless and the flowers are different. And the root burns when you bite it.
Map Source:
USDA Plants Profile
Photo Credit:
https://commons.wikimedia.org/w/index.php?curid=539878