Fallopia japonica

About

Reynoutria japonica, synonyms Fallopia japonica and Polygonum cuspidatum, is a species of herbaceous perennial plant in the knotweed and buckwheat family Polygonaceae. Common names include Japanese knotweed and Asian knotweed. It is native to East Asia in Japan, China and Korea. In North America and Europe, the species has successfully established itself in numerous habitats; it is classified as a pest and invasive species in several countries. The plant is popular with beekeepers and its young stems are edible, making it an increasingly popular foraged vegetable with a flavour described as lemony rhubarb.

Summary from Wikipedia