Butomus umbellatus.

Botanical name: 

Butomus umbellatus Linn. Alismaceae. Flowering Rush. Grassy Rush. Water Gladiolus.

Europe and adjoining Asia. Unger says, in Norway, the rhizomes serve as material for a bread. Johns says, in the north of Asia, the root is roasted and eaten. Lindley says the rhizomes are acrid and bitter, as well as the seeds but are eaten among the savages. In France, it is grown in flower gardens as an aquatic.

Sturtevant's Edible Plants of the World, 1919, was edited by U. P. Hedrick.