Reynoutria japonica, also known as Fallopia japonica and Polygonum cuspidatum, is a herbaceous perennial plant belonging to the Polygonaceae family, which includes knotweed and buckwheat. It’s also known as Japanese knotweed or Asian knotweed. It is native to Japan, China, and Korea in East Asia. The species has successfully established itself in a variety of habitats in North America and Europe.

It has been utilized in traditional Chinese and Japanese medicine to treat different diseases through the activities of resveratrol. The content of resveratrol extracts from R. japonica roots is higher than that of stems or leaves, and the levels are maximum at the conclusion of the growing season.