Anybody else here struggling with Japanese Knotweed?

Spirogyra

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

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

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

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

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

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

I own it.....

Spirogyra

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

baaba maal

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

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

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

****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

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

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

+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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

Niall_daaS

my3cents wrote: »

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.

I've read some source that say burning would be the only propper way to handle remainders responsible.

my3cents

Niall_daaS wrote: »

I've read some source that say burning would be the only propper way to handle remainders responsible.

The problem in Ireland is getting permission to burn, not an issue in the UK. Most of the source material is from the UK and even Irish sources often refer to DEFRA documents.

yellowlabrador

a walk way near the river here in Dunmanway has been closed off for 5 years. Co cork has hired a man to get rid of the knot weed. It's really bad and it's got worse over the past year. It's over 6 foot tall in places and walking down the path was like entering a tunnel. apparently the path will be close for 5 years. I'll miss it because I loved going there with the dog.

sheesh

my3cents wrote: »

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.

you don't have to cut it off completely just slice- bend over but for a big lot I suppose just spray and spray again when they come back up.

I'm after the first spray last year and keeping an eye it at the moment

recedite

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...

I wouldn't worry too much about it. It cannot compete against spruce woods, or live in an exposed upland situation. These old ruins in the woods are usually in a sheltered spot with a small stream (that was the peoples water supply) so just the ideal spot for JK, but it won't necessarily move from there.
There is a clump of it at a bridge near me, which clump is about 2m wide by 4 or 5m long. Has been there for many years, unchanged. Nobody touches it. Its amazing how quick the stems shoot up in summer, it looks like its going to take over, but then it vanishes again and its back to square one. I think because it's bounded by a tarred road on one side and some trees on the other.
I know its really hard to kill, but I don't think its as invasive as people are making out. It needs a reasonable amount of light and it likes shelter and moisture. So if you could get willow or sally trees established in its place they would probably out-compete it.

yellowlabrador wrote: »

a walk way near the river here in Dunmanway has been closed off for 5 years. Co cork has hired a man to get rid of the knot weed. It's really bad and it's got worse over the past year. It's over 6 foot tall in places and walking down the path was like entering a tunnel. apparently the path will be close for 5 years. I'll miss it because I loved going there with the dog.

Are you sure this isn't Giant hogweed, contact with it can cause skin rashes? It seems unlikely that JK would close off a path, unless nobody was using it.


A local guy who fancies himself as an amateur naturalist/historian was doing a guided walk thing as part of a summer events series last year, and as we all walked past the aforementioned patch of JK, he announced it was Himalayan Balsam and then went on a rant about invasive species.
Thankfully he has never actually tried to hack at it though; all talk and no action.
Anyone who has tried to get rid of a patch of nettles or brambles knows they are hard to kill and that they keep coming back, but yet they don't carpet the entire landscape. So just because a plant is doing well in one spot right now, does not mean its going to take over the entire country by this time next year if its not killed off.

sheesh

tampopo wrote: »

Nobody cares. Report away.

in fairnesss I have noticed al lot of brown patches along the main roads here in kerry where some spraying has obviously been done so someone is out doing something here

Kazbah

Hello all,

I have about 0.5 m2 about 0.75m high of JKW in my back garden. I notice that two bordering gardens are completely overrun with this & bindweed. Am I wasting my time trying to contain my bit if these gardens are not maintained? Also I'd like to pave that area - is that a bad idea in the short term? Any advice?

Thanks

my3cents

Kazbah wrote: »

Hello all,

I have about 0.5 m2 about 0.75m high of JKW in my back garden. I notice that two bordering gardens are completely overrun with this & bindweed. Am I wasting my time trying to contain my bit if these gardens are not maintained? Also I'd like to pave that area - is that a bad idea in the short term? Any advice?

Thanks

Don't do anything yet, and don't cut it down. Wait till the last week of August (later is better but harder to get the timing right) and hit it with as much Glyphosate based weedkiller (like Roundup or one of the cheaper alternatives) as you can. Spray your bit and as much of the bordering gardens as you can get away with. Better still get permission and spay all the knotweed in those gardens as well.

NOTE TO ANYONE WITH JAPANESE KNOTWEED - THE LAST WEEK IN AUGUST AND THE FIRST COUPLE IN SEPTEMBER ARE THE MOST EFFECTIVE TIME TO SPRAY WITH GLYPHOSATE.

Kazbah

Thank you. How long would be safe before paving? I've read here that it takes 3 years to get it under control 😧

monkeynuz

my3cents wrote: »

Don't do anything yet, and don't cut it down. Wait till the last week of August (later is better but harder to get the timing right) and hit it with as much Glyphosate based weedkiller (like Roundup or one of the cheaper alternatives) as you can. Spray your bit and as much of the bordering gardens as you can get away with. Better still get permission and spay all the knotweed in those gardens as well.

NOTE TO ANYONE WITH JAPANESE KNOTWEED - THE LAST WEEK IN AUGUST AND THE FIRST COUPLE IN SEPTEMBER ARE THE MOST EFFECTIVE TIME TO SPRAY WITH GLYPHOSATE.

Absolute rubbish, I've said on here numerous times, the sooner you start the better, July onwards is perfect. Leave it too long and the plant isn't actively growing and won't take the chemical down.

And stem injection is the most effective way of killing it combined with spraying top and underside of leaves.

Why do you insist on giving duff advice?

recedite

I'd agree that now is a good time to spray, while plants are still actively growing. It will start raining again some time in September, and any spray will be useless then.

my3cents

monkeynuz wrote: »

Absolute rubbish, I've said on here numerous times, the sooner you start the better, July onwards is perfect. Leave it too long and the plant isn't actively growing and won't take the chemical down.

And stem injection is the most effective way of killing it combined with spraying top and underside of leaves.

Why do you insist on giving duff advice?

If you bother to read the reports and fact sheets online about Japanese Knotweed then you'll find that other people with first hand experience have found September the best month for spaying for maximum effect.

One example would be from the Invasive Species Ireland website http://invasivespeciesireland.com/toolkit/invasive-plant-management/terrestrial-plants/japanese-knotweed/ where they state Mid to Late September being the ideal time for spaying glyposate. However my own experience from controlling the Japanese knotweed on my own land, adjoining farm land, neighbors gardens and some amenity areas the council never bother with is that the weather isn't always ideal that late so I plan the main spray of the year from the last week of August. The land around here is also exposed to the sea and I find the Japanese knotweed here has lost many of its leaves by the last week in September so I time my main attack a week earlier.

It doesn't mean I don't spray earlier in the year because I do but I still follow up with a later spray from the end of August. Earlier spaying is for two reasons one is to get the growth to a height so you can get into it for a late spray and the other is to follow up on small areas of regrowth. I have two areas to be sprayed in the next couple of weeks. Both were sprayed twice earlier in the year but all I was spraying was tiny bits of fasciated (deformed) growth because I had the maximum impact from a late spraying last year. Previously you couldn't walk across either site it was so dense with knotweed.

I've injected small isolated clumps and it gives great results but its not practical for me to do that on larger areas.

monkeynuz

my3cents wrote: »

If you bother to read the reports and fact sheets online about Japanese Knotweed then you'll find that other people with first hand experience have found September the best month for spaying for maximum effect.

One example would be from the Invasive Species Ireland website http://invasivespeciesireland.com/toolkit/invasive-plant-management/terrestrial-plants/japanese-knotweed/ where they state Mid to Late September being the ideal time for spaying glyposate. However my own experience from controlling the Japanese knotweed on my own land, adjoining farm land, neighbors gardens and some amenity areas the council never bother with is that the weather isn't always ideal that late so I plan the main spray of the year from the last week of August. The land around here is also exposed to the sea and I find the Japanese knotweed here has lost many of its leaves by the last week in September so I time my main attack a week earlier.

It doesn't mean I don't spray earlier in the year because I do but I still follow up with a later spray from the end of August. Earlier spaying is for two reasons one is to get the growth to a height so you can get into it for a late spray and the other is to follow up on small areas of regrowth. I have two areas to be sprayed in the next couple of weeks. Both were sprayed twice earlier in the year but all I was spraying was tiny bits of fasciated (deformed) growth because I had the maximum impact from a late spraying last year. Previously you couldn't walk across either site it was so dense with knotweed.

I've injected small isolated clumps and it gives great results but its not practical for me to do that on larger areas.

Just because they say it doesn't mean they're right, I have had success on a commercial basis of eradicating knotweed the correct way, but if people don't want to follow the correct method that's up to them.

my3cents

I forgot to include the reasoning for the late spraying. The theory is that as the plant naturally moves food reserves from the stems and leaves back into the roots ready for winter it pulls down the glyphosate with it which has all winter to act on the plant.

my3cents

monkeynuz wrote: »

Just because they say it doesn't mean they're right, I have had success on a commercial basis of eradicating knotweed the correct way, but if people don't want to follow the correct method that's up to them.

From a UK (NI) government website http://www.doeni.gov.uk/niea/japanese_knotweed-commonly_asked_questions__2_.pdf

Japanese knotweed can also be controlled by using an approved
systemic herbicide over several years, such as glyphosate, by a
competent fully trained individual. The herbicide should be applied
to the Japanese knotweed leaves ensuring the maximum surface area
is covered. It is recommended to apply the herbicide during the early
stages of the growing season to knock back the forthcoming seasons
growth. This should be followed up with another herbicide application in
September – October time when the Japanese knotweed is dying back
for the winter, to maximise herbicide uptake into the rhizome system.
This process should be repeated in subsequent years until no regrowth
is observed (4 to 5 years usually). Care should be taken to minimise
herbicide spray onto non-target species. Other herbicides are available
for control. The herbicide selected for control is the decision of the
trained individual. They must ensure it does not breach the herbicide
label conditions. Extra care should be taken when selecting a herbicide
for treating Japanese knotweed near water as not all herbicides are
approved for this use. Consideration should also be taken for public
access.

I'm really not bothered if people want to spray it early and keep at it but my point is you get the biggest effect from glyphosate on Japanese Knotweed when sprayed late in the growing season. Once you have it knocked back its still going to regrow and then with the smaller target areas its open season spray every time you see a leaf of it growing, but if possible time it so you have something to spray late in the season so the chemicals are again taken down into the rhizome.

magicbastarder

from a monsanto brochure:
"As with most broad-leaved perennials, optimum control will be achieved from treatment at flowering in August or September but before die-back."

tampopo

sheesh wrote: »

in fairnesss I have noticed al lot of brown patches along the main roads here in kerry where some spraying has obviously been done so someone is out doing something here

There has been something sprayed on JK in Dublin along the Naas road just past the FBD Insurance building at/near the Kylemore Luas station. The leaves are all brown and withered.

Kazbah

Kazbah wrote: »

How long would be safe before paving? I've read here that it takes 3 years to get it under control 😧

Any opinions?

my3cents

Kazbah wrote: »

Any opinions?

The problem is you are most likely going to have to excavate the ground to put in some form of base for the slabs. When you do that you'll break up the rhizomes and increase the problem, you also have the problem of getting rid of any rhizomes you dig up. If you spray as suggested let the plants die down and can work on top of them and put down a layer of builders plastic you stand some chance as the weakened rhizomes may not have the strength to push back up through it. A neighbour has builders plastic (edit> with a good layer of gravel over it to hold it down) under his decking and its kept the Japanese Knotweed that was there down and its never broken through, the JK in that case had been badly buried by the builder a couple of feet down and came back up all over the rest of the site. Whatever you do keep a hand spray of some glyphosate based product to spray any that pokes up between the slabs.

Eph1958

Hi, anybody got any pics of this JK plague so we can keep a look out for it. Many thanks.

Eph