Japanese Knotweed

Japanese Knotweed

Excerpts taken from  www.telegraph.co.uk

What is it?

It's an invasive plant which can seriously damage buildings and construction sites if left unchecked. 

But what is this plant, and where does it come from?

Obviously, Japan.

In the late 1840s, a Dutch doctor called Phillipe von Siebold came to the UK and began to sell Japanese Knotweed to botanical gardens and high society figures.

They wanted to buy a weed?

People did that then. The same thing happened to Giant Hogweed. It's ornamental, or something.

What happened next?

Eventually, by 1869, it became available for public sale in the UK, and farmers started to use it as a feed for their animals.

The late 19th century was a big time for Japanese knotweed: lots of gardeners encouraged its purchase, and one Mr John Wood of Kirsktall called it "a capital plant for the small town garden".

Just before the turn of the century, perceptions changed, and many gardeners began to regard it as an all round Bad Thing.

It quickly picked up a pesky reputation, starting to 'escape' and grow in the wild. In the 1930s, its presence was so intense that it began to reduce house prices in East Cornwall by £100.

In 1981, the Wildlife and Country Act made it an offence to introduce Japanese Knotweed into wild spaces,

In 2011, aphids were released in Swansea to try and combat the crazed plant, without much luck.

Gosh. That's a lot of history for one plant.

Since then, the government is still at a loss for a way to properly control the plant. Oddly enough, no amount of law-making will stop its growth.

Quite. Anyhow, George Eustice, one of the environment ministers at DEFRA, has said that there are "no plans to attempt a national eradication" of Japanese Knotweed, because of the "prohibitively expensive" £1.5 billion cost that is attached.

Network Rail have been prosecuted over knotweed spreading to neighbouring land see more here - https://environetuk.com/blog/Landmark-ruling-on-Japanese-knotweed-encroachment-case

Hang on, what's so bad about it? Why do we want to get rid of it so much?

It has really a wide-ranging root system, which can extend up to 3m in depth and 7m in all directions. These can pose a serious threat to construction works and have devastating consequences to building foundations and drains.

So what we can do about it?

That's the problem - not a great deal. We understand that the plant cannot be dug out of the ground, as it's so difficult to eliminate all of the roots effectively. If less than a grass of its roots is missed in the process, it will rapidly regrow.

You will need a specialist to inject the stems over the course of many months.

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