Bird knotweed

The bird's knotweed, also called Polygonum aviculare, is a plant species within the knotweed family (Polygonaceae).

The dried aerial parts of the plant: leaves, stems and flowers (Polygonum avicularis herba) are used phytotherapeutically.

The bird knotweed is an annual plant whose roots can reach a depth of up to 80 cm; the stems growing upright have a length of up to 60 cm. The elliptically shaped leaves are grass to blue-green in colour. Polygonum aviculare flowers from May to October.
During this time the flowers sit singly or in small groups of up to six flowers together. The flowers are greenish in colour with a white, pink or reddish edge. The smooth nut fruits are 2 to 3 mm in size.

Polygonum aviculare is the parent plant of Polygoni avicularis herba, the herb of the plant, which is collected and dried with the roots during the flowering period.