We battled a problem like this with a tall grass for a long time
years ago. As you say little bits of the plant remained in the soil and
sprouted new growth in a short time no matter how we tried to dig it out.
We eventually had to hand pick the pieces out and put a weed killer on
it, but the thing that really did it was malathion.
I'm wondering also if saturated planting with trees and bushes also
discouraged it because it now gets less sun exposure.
On 7/18/03 12:16 PM Andy Norfolk writes:
>> One of our sites has had Japanese Knotweed identified on it. We have
>> contacted DEFRA, The Environment Agency, The Local Authority and English
>> Heritage but nobody seems to know how to deal with the problem and
>> not from an archaeological perspective. It is in an archaeologically
>> sensitive area and an area scheduled for development in the very near
>> future. It is my understanding the only way to deal with the Knotweed is
>> dig a very big hole and indeed would be an offence under the 1981
>> Countryside act not to.
>I've been battling this beast for most of my professional career as a
>landscape architect - and still am in a current project. It can regrow from
>a piece of root weighing as little as about 0.7g. Strimming it is a disaster
>as all it does is spread pieces about the place which root and grow. Its
>roots can go 2m deep and spread 7m laterally in a single year! This weed
>can be controlled with a glyphosate herbicide, but it will take about 3
>years at least to get rid of it. The best time to spray it is in autumn when
>it is withdrawing resources from its leaves and shoots to its roots. The
>National Trust used a technique in Cot Valley near St Just in Cornwall which
>was very successful, but it's not a legally approved technique and would
>need special permission. The way this is done - only with the right approval
>of course - is to cut the shoots off, pierce the membranes down inside the
>hollow stem with a spike and then inject glyphosate directly into the stem
>using a drench. I should point out that I don't have the necessary
>registration to advise on herbicides so please check all this elsewhere :o)
>It can be contained by covering it with an extremely puncture resistant
>geotextile - the sort used under ballast on railway tracks works. The
>problem with this is that the roots may simply go dormant and regrow as and
>when the ground is disturbed again. It can in theory be excavated and
>disposed of in a properly licensed landfill site, but this hugely expensive
>and most landfill operators wont want it. It can also be excavated and
>spread on another part of the site for treatment with herbicide however this
>needs doing with extreme care to avoid simply spreading it further.
>I'm always willing to help get rid of this stuff!
>Cheers - from Knotweed infested Cornwall