Originally native only to Japan, Taiwan and China, Japanese knotweed was introduced to Europe as an ornamental plant in the 19th century. However, the weed has no natural predators, enabling it to grow rapidly, up to 2cm a day and three metres high overall.
It can grow through tarmac and concrete, breaking the surface open, so it can cause serious damage to our structures.
The plant is common throughout Britain but cannot be cut or manually removed because of its ability to grow from tiny fragments, smaller than a one pence piece.
We have to spray it with a herbicide, which is a slow, expensive process. We spend nearly £100,000 per year controlling giant hogweed and Japanese knotweed.