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Replies

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  David Cox July 20, 2011 at 8:53pm

  It will re-grow.

  The site my allotment is at has this as an infestation currently... You need to go on an erradication programme which will take about 3-6 months At best, possibly the full year.

  On my plot I've been using Clinic Ace (Glyphosate) injected into the stems, and foliar applied spray on smaller shoots (under 1ft). After 6 months it is only sending up very deformed shoots, and hopefully by next spring none at all.

   

  You cant just dig it up, you need to dispose of it in a legal and secure way at a registered site, and tell them what it is - you cant just chop it back, and the roots go very deep... you cant dig it out without going over 1-2m deep.
• PRO

  Gary RK July 20, 2011 at 9:05pm

  I have found Stem Injection very effective using a 50% Glyph mix or blanket spraying if location allows.

   

  You can not just dig up and dispose of...Just the smallest amount left with give another plant. Soil is classed as controlled waste.

   

  The rules are complex. If you don't know or have the desire to, then look at getting someone in (ie subcontract). That not meant to sound condescending, just practical.....
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  Ofer El-hashahar July 20, 2011 at 10:39pm

  or heavy duty plastic sheet on the floor and raised beds with clean soil. start from scratch. mmm?
• PRO

  Nick @ NM Garden Services Ltd July 21, 2011 at 7:39am

  Blanket spraying with glyphosate late in the growing season is effective. Try and let the plants grow so that you have maximum foliage for chemical uptake.
  
  Nick
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  Anthony Toop July 21, 2011 at 8:36am

  See here for some information from the environment Agency about Japanese Knotweed
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  Colin Bell July 21, 2011 at 8:54pm

  Cheers for the link.  I think I'll book mark that one!!
• PRO

  Gary RK July 22, 2011 at 10:14am

  Following earlier discussions on JKW, including useful feedback from Paul, we purchased a simple Stem Injection Kit for a project for a commercial client. To date it has been very sucessfull. We have a regular monitoring program which we record details onto and pass back to client. After 4 visits we have eradicated 90+% of infestation. As we are now in the growing period, we are confident we can deal with the remaining stems showing thru. We also had an area that we could spray and have used the strongest recommended mix and saturate sprayed area. On this area we believe we have 100% success as no new stems have risen.
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  Ofer El-hashahar August 15, 2011 at 1:24pm

  It is commonly used root barriers for knot weeds- search and see- ok perhaps not the thin layers that you think about.

   

  I do not have experience with knot weed but I read a lot on it- as few suppliers asked me to source barriers for that in the past.
• PRO

  Will - WB Design & Construction August 15, 2011 at 11:14pm

  Ofer is right heavy duty geotextiles can be used as a barrier to JK but the need to be of the right spec and suitably installed.
  
  Paul @ PPCH Services said:

  Crazy idea !!! I doubt you have any experience with knot weed Offer?.

   

  The only soloution is a planned spraying/ stem injection program. I too have had good results with stem injection.
  
  Ofer El-hashahar said:

  or heavy duty plastic sheet on the floor and raised beds with clean soil. start from scratch. mmm?
  • 

    Classic Gardens > Will - WB Design & Construction August 16, 2011 at 8:05am

    I also have to agree a building company we worked for used a company who's membrane had a copper and chemical inner which deflected the roots. 
    
    http://pba-solutions.com/content/permeable-root-barriers
    
    No problems have been had by knotweed so far. Please before mocking fellow members look into the evidence first it will only make members less likely to post on the future. 
    
    Will - WB Design & Construction said:

    Ofer is right heavy duty geotextiles can be used as a barrier to JK but the need to be of the right spec and suitably installed.
    
    Paul @ PPCH Services said:

    Crazy idea !!! I doubt you have any experience with knot weed Offer?.

     

    The only soloution is a planned spraying/ stem injection program. I too have had good results with stem injection.
    
    Ofer El-hashahar said:

    or heavy duty plastic sheet on the floor and raised beds with clean soil. start from scratch. mmm?