Reynoutria japonica Houtt (gbif.org link)
Reynoutria japonica, synonyms Fallopia japonica and Polygonum cuspidatum, is a large species of herbaceous perennial plant of the knotweed and buckwheat family Polygonaceae. It is commonly known as Asian knotweed or Japanese knotweed. It is native to East Asia in Japan, China and Korea.
It was introduced into the UK in the early 19th century as an ornamental plant and it is now common and wide-spread as the plant grows rapidly in the wild. Negative impacts include outcompeting native flora, contributing to river bank erosion and increasing the likelihood of flooding. You can find more information on how to identify the plant and how to prevent the spread of Japanese knotweed here.
The leaves and stems of this plant have been researched into as uses for biomaerials and natural dyes in the library.