Koenigia polystachya is a species of flowering plant in the knotweed family, known by the common names Himalayan knotweed and cultivated knotweed. It has several regularly used synonyms, including Polygonum polystachyum, Aconogonon polystachyum and Persicaria wallichii.Koenigia polystachya is native to Asia (southwestern China, Indian Subcontinent, Myanmar, Afghanistan) and it is planted many places as an ornamental. It has the capacity to become an invasive species and has established itself in ...