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.

The word alisma is said to be a word of Celtic origin meaning "water", a reference to the habitat in which it grows. Early botanists named it after the plantago because of the similarity of their leaves.

Medicinal uses
The dried leaves of the water plantain can be used as both a diuretic and a diaphoretic. They have been used to help treat renal calculus, cystitis, dysentery and epilepsy.

The roots have formerly been used to cure hydrophobia, and have a reputation in America of curing rattlesnake bites.