Gardening Club - 2 years on.
3 great Clematis for early season colour

The worst weed - Japanese Knotweed & what to do if you find it

Before the rain got too heavy to do anything, - i've been spending this week weeding a large border ready for planting.

This was one of those borders that have been looked after by "gardeners" - (note the inverted commas) of the type that David Cameron knows about, - e.g the unskilled ones. - (Sorry, not usually political, nuff said, don't get me riled about Garden Janitors, or those who don't know what real gardeners do)

Anyway, I knew that this border had a huge amount of Ground Elder, and Bindweed through it, which would mean we needed to take out all the perennials and get the weed roots out of their rootballs. What I hadn't counted on though was this

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Now those of you who have just said oooh, while sucking in air through their teeth, will know that this is not good news. Those of you who have read the title of this blog, and can guess that it's bad will be waiting to hear how bad, and those of you who have never heard of Japanese knotweed will be thinking that's a pretty plant, - will it fill up my border and flower?

I managed to find Japanese Knotweed in the garden of the 3rd client I ever did a consultation for. A huge stand of it, which in the January I found it looked like burnt bamboo. I went on a huge learning curve of finding out about it, and if you really want to know lots more then the RHS website and the environment agency website are the places to go.

That was why when I moved to my current house 4 years ago and this lovely plant grew in the back border, I found it easy to identify

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Normally when you find a nasty weed, you dig it out, and get rid of it, or at least cut it back regularly to weaken it (a la marestail) but this one is so easily able to grow from the tiniest piece of root, that it is classified as controlled waste, which means you can't just throw it in the rubbish bin, or put it out with the green bags.

That's probably how the stuff gets into gardens, by people who don't know what it is managing to propagate it by mistake by digging it up

If you've got a large amount, then you call in the contractors. - Grace and Flavour our community garden had a huge amount of the stuff, and a local company called EnvironetUK used a fantastic machine to get it out of the ground, and the rhizomes were then burnt,

In a garden, and certainly for this border that i've found it in, We'll leave it alone and use Chemical warfare, and not plant near it (yes i'm usually an organic person, but this is different).

I know that this is the best option because we no longer have the knotweed in our garden, - 2 treatments were all that were needed,

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So Japanese Knotweed, although it was introduced as an ornamental plant in 1825 is not great for gardens, and will spread rapidly from even the smallest root. if you find it in large amounts then you'll need professional help to get rid of it, otherwise, get out the Glyphosate.

Wish me luck, - i'm hoping this lot can be got rid of as thougroughly as mine and Grace and Flavour's

Update - After posting this, I had several conversations with tweeters about the fact that the stem is edible, and tastes (and can be cooked) in the same way as Rhubarb.- I replied that there wasn't big enough pieces for eating, and then - lightning struck twice, and I went to do a new garden consultation at the weekend and found

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yes, this stem does look rhubarb like, - but that's not good for the house owners (who also have regular gardeners who've missed it!) - It's also growing onto the neighbouring golf course, so they are liasing with them about treatment and removal - i'll keep you updated

 

 

Comments

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Ben Lannoy

Nice work on getting rid of knotweed Claire! I've found myself overwhelmed with a bank of it on an almost vertical site. I think it looks like an absailing and Glyphosate job, at least until I give up and call in the pros!

Japanese Knotweed Solutions Guy

Abseiling glyphosate spraying!? Serious gardening!

WiseCharlieD

Nice article. Another thing that you should think about with Japanese knotweed is the law!

As it is extremely invasive it is actually illegal to allow it to grow onto a neighbours property and you can be sued if you knowingly allowed this to happen.

Another point is that banks have been known to refuse mortgages on properties which are affected by it - https://www.wiseknotweed.com/news/article/mortgages-refused-over-japanese-knotweed/ - This unfortunately means that homeowners are either left with a property they are unable to sell or are left with a large bill to treat the Knotweed.

The BBC did a report on Japanese knotweed which is an interesting (and short!) watch which tells you how it can be treated and explains what is is more detail. It is viewable here - https://bit.ly/KpL5ay

Charlie

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