Amphibious Bistort

Polygonum amphibiumThis knotweed has a long rooted non-branching stem up to 1 m in length. The thick oblong leaves float on the water. The 3-5 cm long spike inflorescence composed of bright pink flowers protrudes above water. It blossoms from mid-summer till fall. It is common in shoals and along shores, ditches and roadsides.

The subspecies of the bistort differ so much they can be taken as separate species. The floating subspecies settles in ponds, lakes and rivers – sometimes at great depths. The leaves of the plant are smooth with long reddish stalks and crescent-shaped bases. The terraneous subspecies occurs in wet meadows, on riverbanks, and as a noxious weed in fields and gardens. The plant is uniformly hispid. Leaves have a small stalk and no axilla. The terraneous bistorts almost never flower.

It is used in traditional medicine.

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