Japanese Knotweed

Hi all, I have been asked by a customer who has just moved in to a new house to trim some shrubs and hedges etc. ,  they have Japanese knotweed which they have treated by injecting the correct chemical. At first I said yes and thought I would just stay clear of the knotweed but now I'm concerned that I may spread it to another garden. Does anybody have any experience with this as It's my first encounter and I don't want to end up being liable or spreading the weed. Any advice would be much appreciated, I hope you all have had a fruitful season before the big wind down. Cheers 

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  • PRO

    Might be best talking to whoever is treating the Knotweed on site ?

    Not an expert but if the weed has been treated - surely above ground it is dead / or dying ?

    I believe as soon as the stems are dry / dead they are safe to cut or dispose of --  

    Therefore they should be able to advise at what point you are safe to accidentally cut and bag any stem parts 

    Def no digging the soil near by though !! 

    • Right, ok thans Dan, i'll talk to him, it does look dead above ground

  • PRO Supplier

    Dan has it - it won't spread above ground by anything you do, unless you scatter rhizome fragments around like confetti. Once treated it will die above ground and the dead stalks can be cut and burnt. If a 'live' stem is cut it should not be composted, left on the ground or transported off site unless you have the proper licence - burn it!

    • PRO

      Pro -- is it true it can root from a fresh stem ? I generally thought all above ground matter was safe -- but have read that in some cases fresh stem can root from nodes ? 

      Would also have thought whoever treating site should cut stems down and dispose of as part of treatment process at relevant point ?

      • PRO Supplier

        It is recommended to lay all stems on a sheet to prevent rooting when the stem is laid horizontally as this prompts a growth stimulus if its in contact/ buried in soil - but by far the most danger is disturbing roots/ digging nearby...

  • PRO

    Hi Dan. Hi Pro ;) 

    Every part of the japanese knotweed plant is meristematic ( has regenerative cells at certain points around the plant) except the petiole, flower and leaf.

    In the upper canes most of these cells are clustered around the internodes but as you get lower down the cane more of them are present. The rhizome is by far the most regenerative part of the plant as is the main heart of the crown. As Pro said lay the knotweed on top of a tarpaulin or membrane and allow to dry but make sure it is weighed down or covered  to stop enviromental factors spreading it such as wind or animals.

    Best practice would have a management plan in place with a small sign warning that there is japanese knotweed there to avoid any propagules being transferred outside the property by accident and contravening the EPA 1990. Also any grass within 5m of the knotweed stemps is potentially contaminated material also and any contaminated clippings can inadvertently be picked up by the mower and that then becomes a vector of transmission to sights unknown. This pathway is one of the worst issues when trying to stop the spread of Japanes Knotweed. 

    • PRO

      AJ -- fantastic reply -- thanks very much - very informative 

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