Japanese Knotweed..........again

[Lincs Yellowbelly]

I know there have been numerous threads on this, but most are fairly old.

Has anybody come across any decent methods of controlling this stuff? We have it in 4 different spots in a 6 acre area, I keep cutting it down once a week at least to hopefully try and control it and try to get other species to out compete it.

Any advice?

[ladyhawk]

the best way is in the spring just as it is growing, hope you don't mind hard work for you are going to have to pull it up by the roots takes a while wll maybe a few years ouch.

[Dan Salter]

I have a fight going on.....cutting is not advised partly because 1 gramme of green stem can produce a new plant!!.....

digging out is almost impossible for the same reason as any piece of root left with produce a new plant...and i heard the roots can go down up to 6ft or more!!!!.

Also, if you dig up soil or dig out jap knotweed you are legally obliged to have the soil taken away as contaminated waste!!...

I was going to try and catch mine at the baby stage this year and spray it with herbicide but got bogged down with my degree and its already over head height and spreading more than it was last year.

The accepted but very time consuming method ( and may take 3 years or more) is stem injection!!...yep...each stem is injected with herbicide that then goes down the tube and starts killing the roots.
I may try a simpler method of choping the stems off above ground...and pouring herbicide down the holes...this way you can tell which ones you have done and which you havent ( can you imaging how you would know with injecting?) and then i would safely contain all the cut stems until dry and burn them....

Its worrying as it can break through concrete and destroy house foundations and ours is right up to the drive/wooden garage lean too of the house...its also on NATIONAL TRUST land who seem very uninterested in getting rid!

edit:...the other way is to eat the lot! ha ha its very edible at the young asparagus size stage and cut off and cooked tastes and works just like rhubarb ! ..cut a piece of raw stem and taste it...rhubarb!

[ladyhawk]

never knew you eat it. well you learn something new everyday

[Mercadante]

Don't cut it! Killing it that way, although possible, takes many years, and you risk spreading it, as Dan says.

Spray it with glyphosate (Round-up). I think the very best time to do that is the autumn after it's flowered, because you can poison a lot of leaves that way, just as the plant is sucking down the goodness preparing for winter. But in the spring is good too. You will need to do this for at least three years, probably. I'm on year 2, and the evil weed is certainly looking nervous now.

See the Japanese Knotweed Alliance website for more information.

[Tursiops2]

Originally Posted by Lincs Yellowbelly

I know there have been numerous threads on this, but most are fairly old.

Has anybody come across any decent methods of controlling this stuff? We have it in 4 different spots in a 6 acre area, I keep cutting it down once a week at least to hopefully try and control it and try to get other species to out compete it.

Any advice?

I read an article in the paper (either the Guardian or the Observer) about a week ago about a possible natural control - an insect of some sort - being introduced for Japweed. Unfortunately, the paper has been recycled, and I can't find the article on their website. It seems there's a light at the end of the tunnel though, and not before time.
T2

[Perry Grin]

Originally Posted by Tursiops2

I read an article in the paper (either the Guardian or the Observer) about a week ago about a possible natural control - an insect of some sort - being introduced for Japweed. Unfortunately, the paper has been recycled, and I can't find the article on their website. It seems there's a light at the end of the tunnel though, and not before time.
T2

In it's native range there is a natural insect control, this keeps it the Japweed control there. However, introducing alien species here to deal with it is not without problems and I dare say would be risky to say the least.

[Tursiops2]

Originally Posted by Perry Grin

In it's native range there is a natural insect control, this keeps it the Japweed control there. However, introducing alien species here to deal with it is not without problems and I dare say would be risky to say the least.

Good point and, as I recall, some comment was made in the article about the possibility of native relatives of Japweed being affected. However, as I understand it (and I'm open to correction) Japanese Knotweed (Fallopiana japonica) is in a different family to the native "Knotweeds" (Polygonum spp.), and its closest relative in this country is actually Russian Vine (F. baldschuanica - they've been known to hybridise, I believe)... and that would be no loss .

Am I correct?
T2

[Lincs Yellowbelly]

I understand that cutting it may spread it, but surely only if you move it around to burn? i always just leave it were it lies to rot down. Nothing tends to grow near it if you leave it as it blocks out the light to nettles/brambles.

I'll try and get hold of the clubs round up to start pouring down the stems

[hobble]

Originally Posted by Mercadante

Don't cut it! Killing it that way, although possible, takes many years, and you risk spreading it, as Dan says.

Spray it with glyphosate (Round-up). I think the very best time to do that is the autumn after it's flowered, because you can poison a lot of leaves that way, just as the plant is sucking down the goodness preparing for winter. But in the spring is good too. You will need to do this for at least three years, probably. I'm on year 2, and the evil weed is certainly looking nervous now.

See the Japanese Knotweed Alliance website for more information.

I worked in a garden and used to spray each stem as it was coming up in the spring, I did this for 4 years and eradicated it. You need to be vigilant.
Never move it from the site in which it grows this is one of the reasons it spreads.

[ron1863]

I replied to a similar post about this. We had lots of it on the river bank at the bottom of our garden and we cut it down to ground level, sowed grass seed and mowed it twice weekly with a flymower. In between we were constantly cutting the small red shoots that would pop up but the bank is now weed free.

[mrs fish]

It doesn't spread by root underground then ?

[Mercadante]

Yes, it does spread by root, but also from any little bits of the stem that get blown away or float downstream from where someone has shredded it

[Gill Catton]

Originally Posted by Lincs Yellowbelly

I understand that cutting it may spread it, but surely only if you move it around to burn? i always just leave it were it lies to rot down. Nothing tends to grow near it if you leave it as it blocks out the light to nettles/brambles.

I'll try and get hold of the clubs round up to start pouring down the stems

It may well regenerate from the stems you leave - regardless of where they lie.......

[ChrisJB]

Originally Posted by Mercadante

Don't cut it! Killing it that way, although possible, takes many years, and you risk spreading it, as Dan says.

Spray it with glyphosate (Round-up). I think the very best time to do that is the autumn after it's flowered, because you can poison a lot of leaves that way, just as the plant is sucking down the goodness preparing for winter. But in the spring is good too. You will need to do this for at least three years, probably. I'm on year 2, and the evil weed is certainly looking nervous now.

See the Japanese Knotweed Alliance website for more information.

I've always followed this method, usually spraying in spring. With a bit of persistence, it has done the trick.

Regards, Chris

[ceterach]

Originally Posted by Tursiops2

Good point and, as I recall, some comment was made in the article about the possibility of native relatives of Japweed being affected. However, as I understand it (and I'm open to correction) Japanese Knotweed (Fallopiana japonica) is in a different family to the native "Knotweeds" (Polygonum spp.), and its closest relative in this country is actually Russian Vine (F. baldschuanica - they've been known to hybridise, I believe)... and that would be no loss .

Am I correct?
T2

Hi

I'm afraid you are not. Indeed both Japweed and Russian Vine have been classified as Polygonum species in the past (Polygonum cuspidatum and Polygonum baldschuanicum respectively).

This means that indeed the introduction of a natural predator has potential dangers even if it only to the commercial growers of Rhubarb.

All the best

[Dan Salter]

Originally Posted by Gill Catton

It may well regenerate from the stems you leave - regardless of where they lie.......

I agree with Gill....as i mentioned 1 gram of green stem equals a new plant so you are just reproducing what you cut down in the same spot every year...or even multiplying the problem!

[mrs fish]

What is it like where is it native ?
Sounds like it could take over the world

There is some down the road from me, we had leaflets put in the door about it and to phone the council if you have any in your garden.

[Gill Catton]

biological control always worries me, how do they know that the control organisim won't suddenly prefer something it has never come across before in its evolution like I don't know...... buttercup or loostrife......

[Dan Salter]

Originally Posted by mrs fish

What is it like where is it native ?
Sounds like it could take over the world

There is some down the road from me, we had leaflets put in the door about it and to phone the council if you have any in your garden.

Well its name kind of gives away its native status!...its very tall and leafy and extremely rapid growing with rounded but rhubarb type stems, purple speckles....

at least YOUR council is actively working on the problem...i wouldnt mind tackling my own patches ( actually not on my land its on national trust land but its kind of part of our garden) but the herbicide is soooooo expensive i cant afford to keep up with it, if they supply the goods ill do the spraying.

Oh and in terms of it taking over the world....it has been number 1 on defra's top ten most unwanted alien species list for a while!! Dam those pesky foreign plant collectors....nothing but trouble!

[ron1863]

Originally Posted by mrs fish

It doesn't spread by root underground then ?

It does spread by root but we kept cutting it and we are now weed free with a nice lawn right down to the water's edge. Our neighbour, who left his alone and now has a jungle of knotweed doesn't encroach on ours, probably because we cut the grass weekly and any shoots are cut down. I dare say if we didn't cut it that it would soon take hold again.

[Dan Salter]

Originally Posted by ron1863

It does spread by root but we kept cutting it and we are now weed free with a nice lawn right down to the water's edge. Our neighbour, who left his alone and now has a jungle of knotweed doesn't encroach on ours, probably because we cut the grass weekly and any shoots are cut down. I dare say if we didn't cut it that it would soon take hold again.

Although i still dont advise cutting....it will of course eventually kill the plant over time as the leaves never get chance to photosynthesise...but i just worry about all the small fragements flying out from the mower, maybe into the watercourse and in time ALL your neighbours downstream may have a battle too!

[Adam Cheeseman]

Originally Posted by ladyhawk

never knew you eat it. well you learn something new everyday

Certainly can, let's get the WI making Knotweed jam then we can eat it out of existence

Cheers,

Adam

[Adam Cheeseman]

Originally Posted by mrs fish