The Common Water-plantain (Alisma plantago-aquatica), also known as Mad-dog weed, is a perennial flowering plant native to most of the Northern Hemisphere. It is found on mud or in fresh waters.

Margins of lakes, ponds, marshes, channels, slow-moving rivers. Heilongjiang, Jilin, Liaoning, Nei Mongol, Shaanxi, Xinjiang, Yunnan [Afghanistan, India, Japan, Kazakhstan, Korea, Kyrgyzstan, Mongolia, Myanmar, Nepal, Pakistan, Russia, Tajikistan, Thailand, Uzbekistan, Vietnam; Africa, SW Asia, Australia, Europe, North America].

Chemical constituents of Alisma plantago-aquatica include alisol A 24-acetate and alisol B 23-acetate. The content of these two compounds are significantly different in Rhizoma Alismatis of different areas. It is a hairless plant that grows in shallow water, consists of a fibrous root, several basal long stemmed leaves 15–30 cm long, and a triangular stem up to 1 m tall.