Japanese knotweed in the river

When I moved to Cwm Morgan 12 years ago I was ignorant in the ways of Japanese Knotweed. Once I found out more about the luxuriant growth sprouting tall from 3 metres of our earth and stone boundary I realized that it was something I wanted to remove. I tried “Roundup” weed killer and come November the green went brown and died back. Result! I thought – wrongly. The following summer it was back again with avengeance. Well not so much back, as never having gone – I didn’t realize that the dying back was what all healthy Knotweed does over the winter.

Japanese Knotweed has an extensive underground root network that can extend several metres around and beneath. It spreads, not by leaving seeds behind but by growing from pieces of the plant or root system that are cut and transported by people or by water. A fragment of root as small as 0.8 grams can grow to form a new plant. This is one reason it is illegal in the UK to dispose of it on landfill sites.

The photo on the right taken today shows a growth of Japanese Knotweed in the middle of the stream running though Cwm Morgan not far from my office (click for larger image). I know this is only months old, because every winter the stream rises by at least half a meter and occasions become a flooding, raging torrent, washing the bed clean.

Japanese Knotweed was introduced to the UK as an ornamental plant during the 1800s. The problem is that it’s spread has been voracious. Once established, it shades out native plants by producing a dense canopy of leaves early in the growing season. Although Japanese Knotweed is not toxic to humans, animals or other plants, it offers a poor habitat for native insects, birds and mammals.

So how did I finally get rid of the Knotweed in our garden? I pulled it out by hand, and kept pulling every time it sprouted (It can grow 2cm in a day). Every week or two I would carefully examine the area where I knew it was lurking below the surface and pull, being careful to put the pullings in the wood burning stove. It took three summers, but now it’s all but gone.

But there is plenty more in the village waiting Triffid-like to invade my garden – Aghhhhh!….

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