Alisma plantago-aquatica

The Common Water-plantain (Alisma plantago-aquatica), also known as Mad-dog weed, is a flowering plant native to most of the Northern Hemisphere, in Europe, northern Asia, and North America. It grows in shallow water, and consists of a fibrous root, several basal leaves 15-30 cm long, and a triangular stem up to 1 m tall, with a branched inflorescence bearing numerous small flowers with three round or slightly jagged, white or pale purple, petals.
See more at Wikipedia.org...

Noun
1. marsh plant having clusters of small white or pinkish flowers and broad pointed or rounded leaves
(synonym) water plantain
(hypernym) marsh plant, bog plant, swamp plant
(hyponym) ribbon-leaved water plantain
(member-holonym) Alisma, genus Alisma