Japanese Knotweed can grow more than 1m in height in three weeks and the elaborate root system can go down 3m and out 7m. It is extremely vigorous and invasive and, if left untreated, can spread, causing structural damage to properties, paths, walls and drainage systems.
It is an offence to allow Japanese Knotweed to spread across neighbouring land and is therefore best treated as soon as it is identified. Ideally it should be treated during early and late Summer with the dead stems (above ground growth) removed in the Winter. However, standard advice is to treat Japanese Knotweed as soon as it is identified.