Although related to common garden weeds, such as knotweed and redshank, the ornamental species make fine decorative plants for garden use, and they have thrived in the long spells of damp weather this year.Persicaria campanulata is native to the Himalayan region of China and grows to about one metre tall and wide. It overwinters as quite tight rosettes at soil level and from spring and early summer begins to grow very quickly with tall fleshy stems and heart-shaped pointed leaves.