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SpringHeeledJack 22nd Apr 2012 15:46

Japanese Knotweed
One has found some of this in one's territory and have been informed what a horrible plant it is to get rid of. So...has anyone got a home-remedy that might be poured down the tube of the above plant so as to reduce the root and hopefully dissuade it from spreading ?


vulcanised 22nd Apr 2012 15:59

a home-remedy

From what I've heard, the home remedy is made by JCB !

Good luck with that stuff.

probes 22nd Apr 2012 16:09

I was foolish enough to PLANT a red-leaf variety... but the dogs eradicated it successfully.
So, as for a solution - a dachs and a lab?

Radar66 22nd Apr 2012 16:09

G-CPTN is the resident expert.... It is VILE stuff - grows through thick walls and concrete compromising their stability, and you have to be so careful if you cut it as just the tiniest fragment will propagate itself.

We have it too and I'm just battening it back down bit by bit with Roundup Tree and Stump Remover. Gradually winning, but it is a long process and it rises again anew each year, but marginally less vigorously than before.

I WILL win. I will! :ugh:

G-CPTN 22nd Apr 2012 16:13

As a fully-trained (and certificated) knotweed operative, the answer is high-concentration Glyphosate (Roundup) injected into the stem when they are large enough to accept a needle. You could buy (or beg) a syringe from a pharmacist, however we use custom-made equipment based on that used for injecting sheep:-
Japanese Knotweed Removal by Glyphosate Herbicide Injection

The mixture that we use (neat - not diluted) is commercial grade strength not normally available to the public - though you might be able to get some from a farmer or agricultural chemical supplier.

Full strength glyphosate for total weed control - Weed Killers - Total Weed Killers - Roundup Pro Biactive 360 5LT - Progreen Weed Control Solutions, suppliers of agricultural, horticultural and amenity chemicals

We don't use sprays as the stands are alongside a river which is a main water-course and the Environment Agency won't permit spraying as there is risk of run-off and it is deemed harmful to fish.

You probably know that you cannot move any pieces off-site - not in any form, and certainly not in compost - they can be burned, but don't allow anything to 'float away' as this will risk it spreading.

Take care that you don't carry pieces away on your boots or on vehicle tyres.

It's better to leave the plants intact.

Spraying (as Rads is doing) would be the best solution for small plants that cannot be injected. Do it repeatedly until you win.

What you have to realize is that Knotweed propagates from underground rhizomes, so the above-ground vegetation is simply the 'flower',

You need to kill the rhizomes by weakening them season after season (don't even consider digging them up unless you can dig deep enough to be absolutely certain that you are way way beneath them - any broken bits will regenerate and grow). Treating the above-ground vegetation with Glyphosate at a time when growth is receding will draw the chemical back down into the rhizome and weaken it.

We get 85-90% success (so 10-15% regrowth the following season).

Keep at it!


charliegolf 22nd Apr 2012 16:36

Where can you get the death gun?


G-CPTN 22nd Apr 2012 16:59

Stem Injection Systems: Products & Enquiries

Don't expect it to be cheap (250) - maybe you could manage with a simpler syringe and needle system?

We used a 'drenching' gun fitted with a needle the first year (although it was a two-person job as someone had to hold up the reservoir - though you could sling it over your shoulder). You might be able to acquire one from a shepherd.

We wear protective clothing (disposable paper overalls including hood, wellingtons and facemask or goggles) but if you take care not to spill the concentrate on yourself or contaminate your food you should be OK IMO.

Washings from containers should be disposed of by spreading the diluted mixture onto unwanted vegetation away from ponds or streams.

Mr Optimistic 22nd Apr 2012 17:08

Think you can still get proper strength roundup from Central Woolgrowers. Think I would cut it back and then spray new growth: again, and again and again. With trees, digging a hole into the roots and pouring in neat roundup works but it is against regs and in this case not a good idea to dig anywhere near the flaming stuff. Think I would keep the cuttings in a plastic bag, soak with paraffin and burn.

SpringHeeledJack 22nd Apr 2012 17:14

Thanks for the replies. In this case it is in the corner of a garden and most likely the infestation came from an ex-neighbours garden and the rhizomes just pushed up some flowers in mine! What would be the effect if one were to pour acid of some kind down the tube/stem of the plants ? I'm sure that some of he drain clearing nasty stuff might have an effect. The area affected has no water/walls etc close by btw.


G-CPTN 22nd Apr 2012 17:24

What would be the effect if one were to pour acid of some kind down the tube/stem of the plants ?
I've no idea. You could try it and see if it has any effect.

The area affected has no water/walls etc close by btw.
I would follow Radz's method in this case.

Another possibility is to use SBK Brushwood Killer mixed with paraffin and/or old engine oil - but that's just a guess (I use it on ivy which has spread through walls and other persistent weeds such as ground elder). No guarantees.

I forgot to mention that we wear protective gloves - this is as much to prevent contamination of any food or drink that we might need during the treatment.

vee-tail-1 22nd Apr 2012 18:09

We have it here in this Welsh river valley. Two virulent patches near the mill buildings. Burning, cutting, poisoning with Round-Up, to no avail, and we have been trying for 6 years. At present the only option is containment of the two areas ... digging around the edges to stop the rhizome spreading to buildings. The E.A surveyors have all but given up the fight, the cost and effort to tackle the vast amount of infestation on Welsh & English rivers is not worth the pitiful results. We tried full strength Round-Up and succeeded in destroying large areas of native vegetation and pollution of the river, but no effect on the knotweed. Given time, nature in the form of evolution and ecology will obtain a balance, but for now knotweed is winning hands down.
The latest EA idea to import knotweed eating beetles from Japan may work, but cane toads in Aus are a warning about what can go wrong. :(
Edit to say, some farmers around here are harvesting the dried out stems, they burn very well in straw bale furnaces and provide a useful fuel. Perhaps GM will one day enable us to eat the stuff!

G-CPTN 22nd Apr 2012 18:13

We tried full strength Round-Up and succeeded in destroying large areas of native vegetation and pollution of the river,
Spraying rather than injection?
I'm surprised that the EA allowed that.

vee-tail-1 22nd Apr 2012 18:21

Spraying when the new growth was about one metre high. Life is too short to contemplate injection of nearly an acre in total of knotweed by one mill owner (me)! So long as I can keep the stuff from demolishing my buildings, that's the best that can be achieved.

Mr Optimistic 22nd Apr 2012 18:26

That's depressing reading. Really need a systemic action so can't see acid or caustic soda doing much.

G-CPTN 22nd Apr 2012 18:39

Roundup as sold in garden centres is a mere fraction of the strength of that supplied to farmers (which is intended to be diluted before use, but we use it 'straight out of the container' for injection).

I imagine that that makes a big difference, but, I admit that treating an acre of the weed would be tiring (as well as being expensive).

Vizsla 22nd Apr 2012 18:43

Report it to your local council, some will pay experts to eradicate it

Whirlygig 22nd Apr 2012 18:54

Nasty stuff ....

Environment Agency - Japanese knotweed

Hope this helps.



G-CPTN 22nd Apr 2012 19:14

There is no legal requirement for landowners in the UK to eradicate Japanese Knotweed, though transporting it onto adjacent land is forbidden without a licence. It is also an offence to cause it to spread.
Disposal (other than in situ) must be done at approved sites (and it's expensive to achieve - it must be buried at least five metres deep).

Allowing it to invade neighbouring land can be a civil matter. You can also be held liable for costs incurred from the spread of Knotweed into adjacent properties and for the disposal of infested soil off site during development which later leads to the spread of Knotweed onto another site.
An infringement under the Environmental Protection Act can result in enforcement action being taken by the Environment Agency which can result in an unlimited fine.

Japanese knotweed Law

Environment Agency - Japanese knotweed

Japanese knotweed law | Japanese knotweed legislation

TBirdFrank 22nd Apr 2012 19:29

It took me two seasons to win.

Do NOT try to dig it out. All you will succeed in doing is spreading it as any severed piece is viable. It truly is awful stuff!

To succeed, first I sprayed the weed with a normal broad leaved killer. Everything above ground dies and can be burnt off, as it dries like weak bamboo, and on a dry day the dead stems burn like kindling

Then you can see the hollow rhyzomes at ground level with their hollow centres.

As G-CPTN says, take - neat - not dilute Glyphosate or similar systemic and simply pour it into the hollow void.

Two applications did it for me.

Milo Minderbinder 22nd Apr 2012 19:30

I got it out of my - small - garden by hoeing everything off, burning it, then deep double digging the ground three times in as many years, each time removing and burning any roots I found. In between diggings, any shoots appearing were hoed and burnt. After three years the ground was clear. Eventually you will kill it, but its a lot of work and takes years
When I say deep double digging - I mean around three feet. You have to get - as far as possible - every trace of root out

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