Pink knotweed - Persicaria capitata

''Persicaria capitata'', the pink-headed persicaria, pinkhead smartweed, pink knotweed, Japanese knotweed, or pink bubble persicaria, is an Asian species of plants in the genus ''Persicaria'' within the buckwheat family. It is native to Asia and grown as an ornamental in other countries. It has become naturalized in Australia, South Africa and a few scattered locations in the United States.