Anybody else here struggling with Japanese Knotweed?

Spirogyra · 01-06-2015 9:57am #1

Does anyone know if there is any spray available from a typical garden centre? simply cutting it down is of little use as the roots are the problem? worried....

Chloris · 01-06-2015 10:06am

My brother has a problem with it. It grows up through the decking in his back garden. He got in a pest control crowd but they just delayed the re-emergence. According to him there is just no killing it.

looksee · 01-06-2015 10:11am

http://www.corkcoco.ie/co/pdf/786446050.pdf

I haven't had to deal with it, but this is what Cork CoCo have to say about it.

catastrophy · 01-06-2015 10:55am

Its a scourge alright and you have my sympathy.

You will need a systematic approach. Is it in an area you can spray with a glyphosate based weedkiller like roundup? If it is spray it. You may need an awful lot of glyphosate however. When green shoots emerge then spray them. Continue ad infinitum. Unfortunately you will turn the area into a wasteland but it will recover once the jkw is gone. It will take persistence mind you.

Id be inclined not to try to dig it out initially. It will break and spread.

Theres plenty of info available. Im just speaking from first hand experience, so there may be better solutions for your particular area.

Spirogyra · 01-06-2015 11:04am

catastrophy wrote: »

Its a scourge alright and you have my sympathy.

You will need a systematic approach. Is it in an area you can spray with a glyphosate based weedkiller like roundup? If it is spray it. You may need an awful lot of glyphosate however. When green shoots emerge then spray them. Continue ad infinitum. Unfortunately you will turn the area into a wasteland but it will recover once the jkw is gone. It will take persistence mind you.

Id be inclined not to try to dig it out initially. It will break and spread.

Theres plenty of info available. Im just speaking from first hand experience, so there may be better solutions for your particular area.

Thanks, it's in a bit of a small 'wasteland' ,circa 1/4 acre adjoining my property, but bordering a service station,getting worse every year and touching actual structures..... this spray, would I require a mask? or any special clothes? likely I'll approach a local garden centre soon....

Reckless Abandonment · 01-06-2015 11:59am

Spirogyra wrote: »

Thanks, it's in a bit of a small 'wasteland' ,circa 1/4 acre adjoining my property, but bordering a service station,getting worse every year and touching actual structures..... this spray, would I require a mask? or any special clothes? likely I'll approach a local garden centre soon....

Any idea who owns the waste land. You'll need to get them to sort it on their property or you're wasting your time.. Jkw is about as bad as weeds get

Spirogyra · 01-06-2015 12:12pm

I own it.....

Spirogyra · 01-06-2015 12:24pm

came across it a few times on a walk this morning, seems to be taking over the country....

baaba maal · 01-06-2015 1:08pm

It sounds as if you have a proper infestation alright. If I were you I would "tool up" with a proper knapsack sprayer and get a large container of glyphosate (Roundup is the usually quoted brand name but i think it is dearer)- from an agri supplies place. i would also get proper mask, gloves etc. Most importantly- don't exceed the recommended strength, you will be just wasting money. Glyphosate is foliar (apply to leaves) and systemic (travels from leaves into the rest of plant) so you want to apply it to as much of the leaf surface when the plant is actively growing to ensure the glyphosate is absorbed. Ideally after some rain (no problem there) but maybe when the temp goes up a little and when there won't be any rain for preferably a day after application.
The bad news is that you will need to do this a few times this year (I would wait for three weeks to allow it to work and to check for any missed patches). I would then hit the regrowth hard. You probably need to check adjoining properties- no point in clearing your own just to see it recolonise from next door.
The good news is that if you are diligent with it you WILL remove it.

lazybones32 · 01-06-2015 9:24pm

Having JK on your property isn't illegal but you are required to control it and prevent it from spreading. Ragwort is supposed to be controlled too but no-one has been fined, afaik, for not dealing with it on their land. So don't freak out thinking that you could be 'done' for having it on your property.

How bad is the infestation and how tall is the plant? If the 0.25 ac/ 500 sq. M area is nearly covered with the weed, you might be better served by getting professional help. Contact the local Tidy Towns and see if they can assist you or if you know someone in the County/Town Council, their help could be invaluable: they have all the gear, the chemicals and the experience of spraying herbicides. If you ask the right person in the Council, they will be very helpful but if you happen upon the wrong one...

DIY: A knapsack (16-25L) will be needed with an extended lance. A 5l drum of Round-Up Pro-Biactive (or Glyphosate-based herbicide) because repeat applications will be required and safety gear (a proper respirator - not the white dust masks, gloves, wellies and something to cover your hair. Limit the amount of skin that could be exposed to spray - so no shorts/t-shirt).

The mix-rate for Glyphos is between 10-25mls per litre of water. I use 10mls and it takes about 15 days for the spray to take effect. Spray - not douse - the top and the underside of the leaf, if possible. The more the plant absorbs, the sooner it dies.

my3cents · 01-06-2015 9:25pm

I have it under control on our land and a few other places near us after about 10 years, 3 years gets 99% of it. Getting rid of the main mass of the infestation is easy enough with any glyphosate based weed killer but its getting the last bits that are the problem. Give up and they'll soon spread it back.

Now I'm using a home made glyphosate gel to paint the stragglers.

Main tips would be don't give up, a late spray in August of the mature foliage is worth 2 or more sprays earlier on. Second year after a good hit with glyphosate it often goes dormant so looks like a really good kill but it comes back in the third year. In the second year keep spraying any small bits of regrowth (monthly). Totally wet the leaves on both sides if possible, for really thick infestations over large areas when using a knapsack sprayer take the swirler out and use the spray like a water pistol to really wet the foliage. Be careful not to spread it around because it can root from any live cut stems.

Injecting the stems also works really well, but again leaves bits around the main clumps that need follow up treatment.

I've just taken on eradicating Japanese Knotweed on a neighbors site about half an acre. Started last year just cutting down and spaying some paths through it, this year I've cut down the dead foliage so can get around the site to spray the rest of it. Intend to hit it at least twice this year hopefully three times, that should get a lot of it so there will be a lot less to spray in future years.

Markcheese · 01-06-2015 9:35pm

****e- just seen the photos on cork coco website and that's what's spreading from my neighbours jungle - at the moment it's overshadowing the wild clematis stuff ( old mans beard maybe ?) and the bind weed, briars and nettles that pass for foliage over there but to it's credit it's spreading fast - round up it is so -

arthur daly · 02-06-2015 5:41pm

Ring national agri chemicals in Dublin get the jo off Google,they will be best able to advise a chemical as it is horrible stuff to get rid of

my3cents · 02-06-2015 6:01pm

I've used a whole load of different herbicides on Japanese Knotweed. Glyphosate is the only one that works. As previously stated best effect is when the mature foliage is wetted with Glyphosate at the end of the summer. The problem with a late summer treatment is the foliage can be so high and the "crop" so thick its very difficult to get in and spray all the "crop".

Casaron G4 (Dichlobenil) is also quite good against Japanese Knotweed as a residual herbicide on paths and under decking but I'm not sure its available here anymore.

mud · 11-07-2015 4:53pm

+1 on not digging it out. We tried this and the situation is definitely worse. Will look into spraying it at the end of the summer. Invasive is the word!

my3cents · 11-07-2015 5:03pm

mud wrote: »

+1 on not digging it out. We tried this and the situation is definitely worse. Will look into spraying it at the end of the summer. Invasive is the word!

Whatever you do it can often look worse before it gets better. Glyphosate can get a good kill on the crowns but that still leaves all the roots that run for up to 7m, so 12 months later it can look like its covering a far bigger area than you stared with when all the root tips start to sprout.

mud · 11-07-2015 5:06pm

my3cents wrote: »

Whatever you do it can often look worse before it gets better. Glyphosate can get a good kill on the crowns but that still leaves all the roots that run for up to 7m, so 12 months later it can look like its covering a far bigger area than you stared with when all the root tips start to sprout.

Digging it caused major problems with spreading. The roots are easily 12 feet and now the patch is definitely bigger than the last few years. Da cut the acre yesterday for silage and we could see that the JK is worse.

my3cents · 11-07-2015 5:19pm

mud wrote: »

Digging it caused major problems with spreading. The roots are easily 12 feet and now the patch is definitely bigger than the last few years. Da cut the acre yesterday for silage and we could see that the JK is worse.

Its that end of season soaking with glyphosate that does the most damage. If its cut now then let it grow away spray it really well in early in September before it looses its leaves for the winter.

At home here I'm down to chasing a few bits that come up in the "lawn" and rough area of grass along a river bank. To save making a mess in the grass (had years of big areas of killed off grass) I'm spot weeding with glyphosate mixed with wall paper paste and painting the leaves. The spot weeding seems to be working and I'm going back to fewer and fewer spots each month.

If its been cut then spraying the cut stems is also worth while, quite good in fact if you can fill the hollow stems with a glyphosate mix.

monkeynuz · 11-07-2015 5:38pm

It needs to be tackled now by injecting the stems with 1:1 roundup pro bi active about 20ml per stem then spray over the top and underside of the leaves with 5:1 solution I did this 4 years ago for a customer and it killed it within 2-3 weeks with no reemergence only a few bits I had missed. Just burning the tops doesn't work and it needs to be this time of year because the plant is actively growing.

Niall_daaS · 13-07-2015 4:01pm

I was walking in Wicklow recently and I might have been stumbled over jap. knotweed. Was basically an abandoned and derelict house next to an old forest path in the middle of a new spruce plantation. Must check my pictures again to make sure it really was jap knotweed but assuming it was, where should I report this? Guess the land is not maintained beside the regular forest works and I don't believe the owner is aware of this.

my3cents · 14-07-2015 10:53am

Niall_daaS wrote: »

I was walking in Wicklow recently and I might have been stumbled over jap. knotweed. Was basically an abandoned and derelict house next to an old forest path in the middle of a new spruce plantation. Must check my pictures again to make sure it really was jap knotweed but assuming it was, where should I report this? Guess the land is not maintained beside the regular forest works and I don't believe the owner is aware of this.

I doubt anyone is interested in knowing. I spray off a load of areas near me that the council don't bother with. I know the road gang that cover the area and one of the guys was sent to do a course that included information on the impact and control of Japanese knotweed but that's as far as it goes no one is actually going to do anything about it.

I even noticed recently that Waterford council flail mowed at least one large area of Japanese knotweed on the new Greenway and if you want to speed the spread knotweed the best way to do it is to drive heavy machinery over it and flail mow it.

Niall_daaS · 14-07-2015 1:08pm

my3cents wrote: »

I doubt anyone is interested in knowing. I spray off a load of areas near me that the council don't bother with. I know the road gang that cover the area and one of the guys was sent to do a course that included information on the impact and control of Japanese knotweed but that's as far as it goes no one is actually going to do anything about it.

I even noticed recently that Waterford council flail mowed at least one large area of Japanese knotweed on the new Greenway and if you want to speed the spread knotweed the best way to do it is to drive heavy machinery over it and flail mow it.

Luckily I was never confrontated with any issues referring the knotweed yet, but according to everything I've heard so far from others I'm a little bit concerned about finding it uncontrolled in the open landscape. It's not WMNP area but how easily will it spread?

my3cents · 14-07-2015 6:03pm

Niall_daaS wrote: »

Luckily I was never confrontated with any issues referring the knotweed yet, but according to everything I've heard so far from others I'm a little bit concerned about finding it uncontrolled in the open landscape. It's not WMNP area but how easily will it spread?

Sorry I seem to have lost a long reply to your post :mad:

All the plants in the UK and Ireland are genetically Identical because they are all sisters having come from a single plant originally introduced to the UK. We only have the female plant and they have got around the country by root and stem cuttings.

On a construction site a digger can pick up the roots in a track and transfer the plant to the next site its used on. Soil moved from site to site is an obvious method of propagation. Someone slashing down the live stems on a river bank will likely transfer the weed downstream where the stems wash up. The roots often get washed out of the side of river banks and can in ideal conditions travel down stream out to sea and from Ireland all the way over to the UK rooting where they get washed up.

Flail mowing the stems on verges and waste ground can quickly spread the them on site and with the stems being moved about by traffic quite a good distance from the original plants.

I've know kids cut the live stems to play fight with, the discarded stems can root where left. Worst of all some people not knowing what it is will dig it up and plant it in their garden. You could also get it in your garden after picking up a bit of root on walking boots or on bought in top soil.

In my own garden (a cultivated field) I'm fairly sure that Japanese knotweed stems and crowns (the part of the root connected to the above ground growth) were picked up in a storm from the beach and dumped in my garden (close to the sea) and left to root. The garden/field floods and all the most mature plants ran along a line that I know is where the beach debris gets dumped in an extreme storm/flood. Another possibility is that someone upstream cut down a load of stems just before the garden/field flooded.

Its said that the a piece of root as small as a fingernail can produce a new plant. I've dug out new plants caused by trying to dig the roots out and bits about a 1cm long and 5mm round have no problem creating new shoots.

Niall_daaS · 14-07-2015 6:56pm

my3cents wrote: »

Sorry I seem to have lost a long reply to your post :mad:

All the plants in the UK and Ireland are genetically Identical because they are all sisters having come from a single plant originally introduced to the UK. We only have the female plant and they have got around the country by root and stem cuttings.

On a construction site a digger can pick up the roots in a track and transfer the plant to the next site its used on. Soil moved from site to site is an obvious method of propagation. Someone slashing down the live stems on a river bank will likely transfer the weed downstream where the stems wash up. The roots often get washed out of the side of river banks and can in ideal conditions travel down stream out to sea and from Ireland all the way over to the UK rooting where they get washed up.

Flail mowing the stems on verges and waste ground can quickly spread the them on site and with the stems being moved about by traffic quite a good distance from the original plants.

I've know kids cut the live stems to play fight with, the discarded stems can root where left. Worst of all some people not knowing what it is will dig it up and plant it in their garden. You could also get it in your garden after picking up a bit of root on walking boots or on bought in top soil.

In my own garden (a cultivated field) I'm fairly sure that Japanese knotweed stems and crowns (the part of the root connected to the above ground growth) were picked up in a storm from the beach and dumped in my garden (close to the sea) and left to root. The garden/field floods and all the most mature plants ran along a line that I know is where the beach debris gets dumped in an extreme storm/flood. Another possibility is that someone upstream cut down a load of stems just before the garden/field flooded.

Its said that the a piece of root as small as a fingernail can produce a new plant. I've dug out new plants caused by trying to dig the roots out and bits about a 1cm long and 5mm round have no problem creating new shoots.

Sorry, sorry, maybe my words were unclear: I am aware of how Jap Knotweed technically operates. I have at least 2 customers of who I know that they had to deal with it in public areas in order to get rid of it. My worries are that I can't estimate how fast it expands in a not maintained upland area. Is that a minor impact or will the area I saw a couple of weeks ago be largly covered with the Jap Knotweed in say 2 years. You said nobody would really care. Is that something officials should be more aware of? Should I report?

my3cents · 14-07-2015 8:08pm

Spread depends on location and conditions. It spreads fastest when in contact with humans. If it was along a regularly used foot path then I'd honestly expect it to spread along the footpath especially if the footpath was muddy. Just being trashed down on a footpath will make it spread quicker.

What seems to happen is that the plant covers the first few square meters very quickly then slows down and consolidates.

The field I'm attacking with a neighbor is completely covered to the extent that no light at all gets through to most of the soil. Ten years ago the field was about a third covered. Its path is blocked on one side by a river (densest near the river hence where it probably started) so it would have covered 6 times as much area in that ten years if in open ground.

There are really two issues I think, one is the spread if not touched in anyway and the other is the spread if its in areas were people walk. The obvious first course of action would be to prevent traffic (foot, hooves, tracks and wheels) over any areas where there is Japanese knotweed or divert it around those areas.

The problem is as much how fast it spreads into new areas as how fast an existing infestation expands.

looksee · 14-07-2015 8:29pm

I also have the impression that there is no real interest at an official level. The only thing is that if enough people keep reporting it someone somewhere may eventually say 'there seems to be a lot of this stuff maybe we should do something'. In fairness at an individual level the county council officials are a bit overwhelmed because of the recruitment embargo, but these rogue plants need to be reported I think.

my3cents · 14-07-2015 8:34pm

looksee wrote: »

I also have the impression that there is no real interest at an official level. The only thing is that if enough people keep reporting it someone somewhere may eventually say 'there seems to be a lot of this stuff maybe we should do something'. In fairness at an individual level the county council officials are a bit overwhelmed because of the recruitment embargo, but these rogue plants need to be reported I think.

Even if the councils managed to get most of the areas they have with Japanese knotweed sprayed with glyphosate once a year would be a good start.

my3cents · 14-07-2015 10:10pm

Found a good Japanese knotweed link it might be for a mirror article but its well researched and the time lapse video is worth watching. http://www.mirror.co.uk/news/japanese-knotweed-everything-you-ever-4328310 .

sheesh · 14-07-2015 10:17pm

Spirogyra wrote: »

I own it.....

jesus you need to get onto that quickly so it can grow through concrete and can damage building and roads if the root system were to ddamage your neighbours property you could be liable.

I was told by a guy in a local garden centre to cut a stem and spray the weed killinto the hollow stems of the plant to increase the up take of the weed killer. Had some on my mother farm we paiod a guy to spray it and he said that you would probably need to do it again the following year it is clear so far.

my3cents · 14-07-2015 10:45pm

sheesh wrote: »

jesus you need to get onto that quickly so it can grow through concrete and can damage building and roads if the root system were to ddamage your neighbours property you could be liable.

I was told by a guy in a local garden centre to cut a stem and spray the weed killinto the hollow stems of the plant to increase the up take of the weed killer. Had some on my mother farm we paiod a guy to spray it and he said that you would probably need to do it again the following year it is clear so far.

Thats true but the problem is you then have the cut stems to deal with and you can't take them to the tip or compost them. Better in a lot of cases to spray or inject what you see and only cut down dead stems.

As I mentioned before it often goes dormant for a year while it shakes off the effects of the glyphosate and then comes back two years later.

tampopo · 14-07-2015 11:34pm

Niall_daaS wrote: »

Sorry, sorry, maybe my words were unclear: I am aware of how Jap Knotweed technically operates. I have at least 2 customers of who I know that they had to deal with it in public areas in order to get rid of it. My worries are that I can't estimate how fast it expands in a not maintained upland area. Is that a minor impact or will the area I saw a couple of weeks ago be largly covered with the Jap Knotweed in say 2 years. You said nobody would really care. Is that something officials should be more aware of? Should I report?

Nobody cares. Report away.

Anybody else here struggling with Japanese Knotweed?

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