[humbug]

Hi,

I work with Japanese Knotweed all the time.  The best approach is to cut the stems back late summer when in full growth and pour stong systemic weedkiller down into the hollow stems.  You cant get the stuff that the contractors use without a licence but I'll see whether i can get some recommendations.  This is considered more effective than spraying.

It wont kill for a couple of years but should keep it in check a little.  Given that it is dying back at this time of year you should cut back canes to about a foot above ground level - possily give it a little more.  These can be burnt as it is only the lower part of the stem that is viable and can be spread. This keeps it tidy and stops the stems from breaking or being blown around in winter.

Hope this helps - on a good note there is site on the internet that give you some recipes for the young shoots.  Apple and Knotweed pie has always looked interesting!

[Yorkie]

Our local contractor injected the glyphosate into the stems, killed them that year and can't see any regrowth (yet).

But, as humbug says, that's industrial strength not amateur strength stuff.