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Over recent months a couple of reports have featured in the full sheet press questioning whether the manic worry over JKW is really justified.

The reports have even questioned whether it’s a ‘self-made’ problem by specialists offering solutions and rhetoric which has made Surveyors and Lenders knee jerk.

These reports agree it’s an invasive weed but much of the capabilities to cause damage are now being questioned.

For further reading hunt down the articles on the Sunday Telegraph and The Times ( I’ll try and post links but some are behind paywalls or logins )

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  • PRO

    I went to a customer the other day and they have 3 small knotweed plants. They have been quoted an insurance backed scheme for 5yr weed control process. Not soil away. How much? £3000...

    It only needs 2 visits per year for the 5 years using leaf and stem treatments.

    • PRO

      Depends on how close it is to the house...

  • PRO

    Extract from article for those unable to access:

    "Dr Mark Fennell of Aecom said: “We found nothing to suggest that Japanese knotweed causes significant damage to buildings – even when it is growing in close proximity – and certainly no more damage than other species that are not subject to such strict lending policies.”

    Contrary to popular belief, the report found that knotweed could not grow through concrete. Its authors said this idea was “simply not supported by any evidence, as it is not possible due to the laws and principles of physics and biology”.

    While knotweed can worsen existing cracks in structures, the plant prefers to grow around obstacles rather than burrow through them.

    Mortgage lenders currently require action if knotweed is found within 23ft of a structure. This is due to the belief that the plant’s roots will grow far enough to damage structures within this zone. But the research found that knotweed roots normally extended up to 8ft and rarely more than 13ft."

    • 124905117?profile=RESIZE_930x

      • just one of about 14 points that the knotweed had buried through a footing and cracked up under a concrete hardstand from a growth next foor. It had started to push bricks apart and caused massive contamination of the earth sub floor . one of the tap roots had penetrated 2.5m down into a damp spot in the room. We had to take out 100 tonnes of contaminated soil from under the building. This isnt an isolated case. Its great when you can safely say that knotweed doesnt extend more than 8 feet but as soon as it finds a structural pathway then it can extend  tens of meters. . Ive seen it grab a path edging from a culverst and move 65 meters around a carp park using the path edging as support and then spreading into a block of flats  grounds and using a tree to protect itself

        124905144?profile=RESIZE_930x

        • 10 minutes hand sieving through some shovel fulls inside a small building
          124905274?profile=RESIZE_930x

          • 124905276?profile=RESIZE_930x

  • Hi... I would suggest That some people have not seen the damage that it can do to buildings. I started dealing with knotweed 20 years ago and back then i saw what decades of leaving the knotweed to its own devices can do to buildings, drainage, infrastructure. Much of this has no been remediated ( although some of it very badly and has ended up spread far and wide with bad practice)

    I do have a lot of respect for people who have done biology or horticultural PHD's but i do think that nothing can beat experience in invasives and i dont agree with these latest headline grabbing theories.

    People get the wrong idea about the cost of knotweed managment strategies. They believe its just a little bit of spraying and praying.

    The costs that a decent contractor charges is not in the spraying or the monitoring for 5 years ( we go back for 10 years to satisfy not only the IBG but our guarantee) the costs are in the documentation, the training, the liability and the choices of chemicals used.  This race to the bottom for price is bad news. Its happened before when there was  the " 1 year guaranteed treatment process" when in fact they where just dropping down a chemical barrier of picloram that finally dissapeared and the knotweed either came out of dormancy straight away or in once case I have waited 9 years for it to regenerate from viable rhizome that was treated with tordon but still I am awaiting for it to kick off.

     

    IBG's?  I never wanted them to be part of the knotweed treatment process anyway and i resisted using them for as long as i could. They never guaranteed anything really and in my mind they where just an excuse to make more money although it did tale some of the cowboys out of the system but at the same time it validated some of the cowboys who managed to circumnavigate the system.

     

    In the end it now does help us get paid as we don't release any documents until we have been paid in ful so we do use the IBG to our benefit.

     

     

     

     

     

     

  • PRO

    If you’re interested in this topic, worth catching last night’s (28/9) Gardeners World on iPlayer for a segment on current views on JKW - updating the current view / approach to dealing with it.

    I wonder whether the PCA or INNSA will issue a statement ?

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