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24/11/2011 at 15:27
I've got my work cut out this year then. One hedgerow is riddled with the stuff. It's going to be a tough fight to get the lot to die. Carefully digging between the roots of the hedge is a big job alone.
24/11/2011 at 15:28
We have two large sections 4x4 metres of Japanese Knotweed in our paddock, as we graze this area a friend has advised that we cut the stems to the last leaf shoot and pour salt and oil in each stem then cover with black sheeting - is this good advice?
24/11/2011 at 15:29
I note from http://www.phlorum.com/identify-japanese-knotweed.html there's a cross between JK and its Giant brother that CAN set seed....? I'm a bit concerned about this:my current problem has what look like seeds on the dead flower heads?

Is it really a good idea to dig it out if a fragment of the rhizome can persist in the soil and regenerate even after 20 years? See . http://www.environment-agency.gov.uk/homeandleisure/wildlife/130079.aspx#How_to_control_Japanese_knotweed
04/05/2012 at 12:30
In
04/05/2012 at 12:44
Sorry hit the wrong button!
In my experience digging it out while it is still alive is a decidedly bad idea as one seventh of a gram of root can result in re-growth.

Having spent wasted time trying to spray the stuff we came up with a more radical approach.In Spring, wait until it have reached at least 75cm high, it needs to be making strong growth.Cut the top off so that you can see down the stem, which is a bit Bamboo like in that it grows in section. Straighten a metal coathanger, and poke this down through the sections as far as you can. Make up a solution of Glyphosate, from the concentrate, then using a hypodermic syringe or similar (you don't need a needle) inject the solution carefully into the stem and keep doing this until the stem is almost full. Then proceed to the next plant. Repeat this in Autumn, when the sap is retreating into the roots and again the following Spring, by which time the plant will really be struggling. Once you are certain it is dead and you may need to wait a further season, then it is safe to dig up and dispose of legally.
We have used this successfully on Knotweed which was over 1.8m high and it didn't endanger any of the surrounding trees or shrubs.
04/05/2012 at 14:18

Yes that's exactly how to do it properly, and you can't throw the stuff in rubbish bins either in case it regrows. Burn burn burn it.

You know we introduced this thug as a garden plant back in the day? Jeeese.

04/05/2012 at 16:02

We had this in our last house. Glyphosate, and lots of it, is the only answer! I found spraying with a stronger than normal solution to be fine, but it took about three years to kill it all. Do not dig it up as you have to dispose of at a licensed site as it is notifiable.

Be aware that it can damage house foundations, so if you're thinking of selling you need to make sure you don't have any within two metres of your property or your buyer may not be able to get a mortgage according to a suyveyor I know!

07/12/2012 at 15:23
If anyone ever needs help removing Japanese Knotweed or needs advice, just call JKSL. Where always happy to help with these tricky things.
13/12/2012 at 10:51

Hi Folks, 

Just to clarify:

"Once you are certain it is dead and you may need to wait a further season, then it is safe to dig up and dispose of legally."

This is not legal - all material should be disposed of in licenced landfill. This is for two prinicipal reasons: 1) rhizome may remain viable for decades and 2) herbicides may induce dormancy, not kill. If you are satisfied that your herbicide treatment has worked, leave the knotweed alone (disturbance is likley to promote regrowth), or as another poster suggested, burn to ash in situ, following excavation.

13/12/2012 at 10:55

Additionally, dont use diesel or salt to control knotweed - neither is effective and diesel (in particular) is toxic to plants and animals. Just a point, but treating a large patch of knotweed with salt would be very expensive...!

13/12/2012 at 14:50

Hi some time ago we were thinking of purchasing a house in Pembrokeshire and in the suryey notweed was found on the land,let me just say that after talking to the surveyer ,the council ,the solicitor i was amazed at the effect Jap Knot can have on the garden AND the surrounding areas,i was warned that it would be my job to get rid of it and if it could be proved  that it had spread to anyone elses property i would be to blame and suffer the cost of removal,my solicitor gave me a phone number of a specialist in Jap Knot who i spoke to,he explained all the do,s and donts about this plant and how to get rid of it,most people who try the job themselves fail, becouse of other problems as well we decided not to buy,i have the phone number of this specialist if anyone wants to talk to him ,he is a very nice chap and knows exactly what he,s talking about ,if i came across Jap Knot again i would not even try to get rid myself i,d call this man for advise, if anyone wants this phone no Email me and ill send it to you , please dont think im scare mongering ,im not as this weed has caused many a tear  for many people  Alan.Shacklock@hotmail.com

Good luck

16/12/2012 at 12:10

going slightly off track - we have knotweed where I live, but a MUCH bigger problem with gunnera!!  someone introduced it to the island 10 or so years ago and it has spread like wildfire, in other peoples gardens, crofts, roadsides, the local village, it is now working its way up the surround hills.  the local management committee have an ongoing plan to irradicate it from public spaces, but on private land it is the owners responsibility.  We moved here just over 2 years ago now and the house had been empty for over 2 years so we had PLENTY of gunnera in our garden.  By this summer we have irradicated it, almost, I found a small piece the other day.  We tackled it with Roundup as per instructions the first year - no effect, the second year much stronger solution and applied it 4 or 5 times during the year. Then when it looked dead dug up the roots which still had signs of life in them and disposed of them safely.  I think it helped that here last year was the driest anyone can remember and gunnera don't like the dry!!  it will be a long process to get rid of it completely from the island, just like getting rid of the mink was!!  Moral of the Story - please,  please, please be very careful about what you introduce to the area especially if you live in a rural area where things can go unnoticed until its too late!!

17/12/2012 at 22:31

@galesrus - sounds like a nightmare and completely agree with your statement RE introducing new species to an area...

Found this online - by the looks of it, Gunnera is definitely another triffid (see page 5 onwards!). 

http://invasivespeciesireland.com/wp-content/uploads/2011/01/Gunnera_tinctoria_ISAP.pdf

17/12/2012 at 22:35

Hi Alan,

Apologies if my posts are bit blunt - some of the methods to remove knotweed just wont work and they are expensive, plus they have a range of further negative impacts upon the environment... Ill leave ranting anymore about it after this post!

Will address your post and add some further info. Before I start, I agree with you! 

“Hi some time ago we were thinking of purchasing a house in Pembrokeshire and in the suryey notweed was found on the land,let me just say that after talking to the surveyer ,the council ,the solicitor i was amazed at the effect Jap Knot can have on the garden AND the surrounding areas,i was warned that it would be my job to get rid of it and if it could be proved  that it had spread to anyone elses property i would be to blame and suffer the cost of removal,”

This is very true, to an extent. The law states that you “should not allow Japanese knotweed (JK) to grow in the wild”. What actually constitutes the wild is a difficult point in itself: proving you did spread JK , following purchasing an already infested property is even harder. However, surveyors at present are jumpy (in some cases reasonably so, quite often, not so much!); I saw a guy declined for a mortgage with one stem of JK in his garden and a huge stand at least 5 doors down (more than 75m away). This might sound reasonable, until you realise he was in South Wales: there are quite a lot of places with a little bit of JK and loads just around the corner! This is not a reasonable approach to dealing with JK.

Further, in terms of control, particularly with respect to excavating JK rhizome; even herbicide treated “dead” JK rhizome - please dont do it. It is exceptionally difficult to tell whether it is alive or dead. Incidentally revised figures for JK rhizome regeneration rates suggest that as little as 0.068g (rather than 0.7g) will produce a new plant. Its hard to tell if its all dead - there could be kilos of it... also remember that stems and leaves will produce a new plant - this is not a scare story, there is scientific literature relating to it (please see Google Scholar). Throwing it in domestic waste, even if it looks dead is very risky and could be interpreted as “deliberate” introduction to somewhere else - “wild” (even if its a landfill site!).

“my solicitor gave me a phone number of a specialist in Jap Knot who i spoke to,he explained all the do,s and donts about this plant and how to get rid of it,most people who try the job themselves fail, becouse of other problems as well we decided not to buy,i have the phone number of this specialist if anyone wants to talk to him ,he is a very nice chap and knows exactly what he,s talking about ,if i came across Jap Knot again i would not even try to get rid myself i,d call this man for advise, if anyone wants this phone no Email me and ill send it to you , please dont think im scare mongering ,im not as this weed has caused many a tear  for many people”

Absolutely, if you are not confident in herbicide application and dont have the time/inclination to follow it up, dont try ad-hoc interventions etc. If you are based in Pembroke, Im sure this specialist is a good deal. In other circumstances, get at least a few quotes - most companies (particularly smaller ones) will charge a lot, for a short-term service. What you should look at is not only the herbicide type etc., but the number of visits “billed” by the company. Companies that undertake to revisit your property for a number of years within your contract (what youre paying for) are effectively acknowledging that repeat site visits will be required. 

However, if you are to going to attempt control, here are some good (and not so good!)

18/12/2012 at 15:21

Hi Dan you are quite right about mortgages and JK we were advised that luckily we did not require one but  would we would have not got one anyway if we had wanted one,and yes the treatment from this chap was over 2 or 3 years and guaranteed  for £500 as i said we didnt buy but but im fully aware of it for the future .

Good luck

19/12/2012 at 21:26

do you have to tell the arthorities you have a problem with knot weed and does it contaminiate your garden tools

19/12/2012 at 21:45

Contaminate your tools??-No

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