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Started by Verdigris on Mar 5, 2021 7:20:07 PM
Japanese Knotweed

Has anyone been infested? Did your manage to eradicate it? Did it cost a lot?

FleurDuMal - 05 Mar 2021 19:30:08 (#1 of 141)

Kill it with fire!

champagnerocker - 05 Mar 2021 19:32:06 (#2 of 141)

I was going to say kill it with fire.

Instead I will therefore suggest that you take off and nuke the entire site from orbit.

cozzer - 05 Mar 2021 19:34:04 (#3 of 141)

Shit in its handbag.

HorstVogel - 05 Mar 2021 19:41:31 (#4 of 141)

Burn as much of it as you can find. Cover the area with thick obaque plastic sheeting. Wait 10 years. It's a right nob.

dottie30 - 05 Mar 2021 19:43:41 (#5 of 141)

You can eat it apparently. Tastes like rhubarb.

HorstVogel - 05 Mar 2021 19:44:27 (#6 of 141)

If I had known.

HerrWalrus - 05 Mar 2021 20:00:07 (#7 of 141)

Paint the roots with poison.

JohnIlly - 05 Mar 2021 20:05:23 (#8 of 141)

You could try the proper green approach, starting with a placard campaign to suggest it should go elsewhere.

Or you could do as suggested and nuke it and paint it with herbicide.

elderberry - 05 Mar 2021 20:05:30 (#9 of 141)

The official advice a decade or so ago was let it grow for a few months, then cut the main stem and pour glyphosate into the hollow centre, then paint more glyphosate on the leaves. Repeat the following year. Don't disturb the soil. Be prepared to spot-kill any stubborn bits. try to avoid getting the weedkiller on the soil - it's less benevolent than the manufacturer suggests, but fine when targeted at a specific plant.

Verdigris - 05 Mar 2021 20:08:44 (#10 of 141)

I've read the RHS treatment notes. I'm happy enough to wage a war of attrition; I'll need a retirement hobby! I'm looking further ahead to if/when my descendants need to sell the gaff. If you have it professionally treated you can get an insurance-backed guarantee. If you do it yourself, the vendor is potentially liable if there is a recurrence.

I haven't bought the place, yet, but I'm trying to get an idea of how much to knock off the asking price to compensate.

WibbleAgain - 05 Mar 2021 20:10:27 (#11 of 141)

From the BBC Gardeners' World website - it also tells you how to get rid of it:

Japanese knotweed and the law

Schedule 9 of the Wildlife and Countryside Act 1981 makes it an offence to cause Japanese knotweed to grow in the wild, either by means of fly-tipping or allowing the plant to escape the confines of your garden.

While it’s not illegal to grow Japanese knotweed in your garden, it is illegal to allow it to spread into wild areas or neighbouring gardens, therefore it’s best practice to eradicate or at least control its spread. What’s more, if you’re selling your property then you will need to remove it. Since 2013, homeowners selling their property are required to check the garden for Japanese knotweed and declare its presence, as well as provide details of a management plan on its eradication.

If you’re buying a property and Japanese knotweed has been found to be growing there, your mortgage lender may require assurances that a management plan for its eradication is in place. Regardless of whether it has been declared or not, it’s important to check for yourself, to avoid any problems later on.

Under the Environmental Protection Act 1990, Japanese knotweed is classed as ‘controlled waste’. This means it’s illegal to add it to home-compost or council-run garden waste bins. You are permitted to burn the waste (ideally after allowing it to dry). Alternatively, you will have dispose of it at a licensed landfill site.

Contact The Environment Agency if you notice that Japanese knotweed has been dumped illegally in the wild.

Verdigris - 05 Mar 2021 20:11:27 (#12 of 141)


Yes, I did similar to some buddleia that came up through the tarmac at the place I'm living now.

Verdigris - 05 Mar 2021 20:13:51 (#13 of 141)

From the BBC Gardeners' World website - it also tells you how to get rid of it:

Similar to the government and RHS advice.

darkhorse - 05 Mar 2021 20:15:13 (#14 of 141)

Remember Arnie's wisdom: if it bleeds, then we can kill it.

Treating it as a retirement hobby is probably a good idea.

MadamGwenver - 05 Mar 2021 20:33:19 (#15 of 141)

I had a problem with it coming through from next door about ten years ago.

Glyphosphate at first sight of a shoot every spring for three to four years.

Haven't seen any for five years or so.

Verdigris - 05 Mar 2021 20:34:16 (#16 of 141)

That sounds hopeful. As long as the JK croaks before me, all will be well.

darkhorse - 05 Mar 2021 21:09:07 (#17 of 141)

Our neighbours are very paranoid about Japanese knotweed. Because we have the scruffier garden, they think we're cultivating all kinds of nasties.

Once in a while I have to reassure them: that's ivy. And that's common bindweed. No, that's a bramble.

AdonisBlue - 05 Mar 2021 21:14:11 (#18 of 141)

A small part of my job is dealing with Japanese Knotweed. Although I don't clear it myself I employ contractors and know the methods they use.

How much is there and where is it?

AdonisBlue - 05 Mar 2021 21:18:56 (#19 of 141)

The best solution has already been offered sort of. You want a systemic weedkiller based on glyphosate.

Apply it twice a year. Once in spring, but more importantly once in autumn. The autumn dose is more effective as the plant takes it back down into the underground rhizomes. It can take 3-5 years to fully eradicate, it will come up again next year but just keep applying the weedkiller.

Don't be tempted to try and dig out the rhizomes you'll never get them all out and you only need cm2 to regrow.

AdonisBlue - 05 Mar 2021 21:21:29 (#20 of 141)

Remember do not take any soil off site, it may contain plant parts and is classed as hazardous waste. Don't be tempted to cut it down when treating with glyphosate. More above ground veg equals better absorbtion of weedkiller.

You can employ a professional. Some of these will inject the weedkiller into the plant stems. But they are very expensive.

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