Japanese knotweed

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Every hour enough plastic to fill two bin bags is washed into our oceans from canals and rivers.

One of the most invasive weeds in Britain, and one of the most well know. Japanese knotweed’s dense growth crowds out native vegetation, erodes riverbanks and causes structural damage.

Close up of Japanese knotweed growing out of water Japanese knotweed, copyright GBNNS

Originally native only to Japan, Taiwan and China, it 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.

This horror 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 process and costly. We spend nearly £100,000 per year controlling Giant hogweed and Japanese knotweed.

Last date edited: 15 March 2018