Japanese Knotweed

[Dathi]

Greetings All Greenfingers,

Who knows about this horrible stuff?

I'm preparing a community project to tackle a serious infestation of Knotweed alongside a local river. There is plenty of info "out there" for dealing with this virulent invasive species and we are chatting to rangers and fisheries officers about this. But I vaguely recall some discussions on DHP about this some years back, and some people seemed fairly knowledgable.

Here is the standard advice:
http://invasivespeciesireland.com/most- ... e-knotweed

http://www.fisheriesireland.ie/Invasive ... tweed.html

http://www.aughty.org/pdf/jap_knot_mgmt.pdf

And a most useful resource from across the pond: http://www.devon.gov.uk/environment/nat ... otweed.htm

Basically, this stuff is a devil to get rid of. Some interesting research has been done on bio-control using wee beasties that exclusively feed on knotweed. http://news.bbc.co.uk/2/hi/science/nature/8555559.stm (And there are plenty of opinions about that).

But I've been wrestling with a circular argument. This knotweed infestation is alongside a sensitive eco-system with lots of rare and special plants. It is also in a SAC (Special Area of Conservation), and on a noted salmon fishing river. Usual methods of control (cutting, uprooting, strimming etc) are no good (in fact, the worst possible thing to do. This stuff sprouts up from the tiniest remnant of a plant) and herbicides are the common recommendation ( Glyphosate ). Typical advice here: http://dnr.wi.gov/topic/Invasives/docum ... ontrol.pdf But herbicides in a sensitive environmental area and alongside a fishery are not ideal either.
In fact, even more radical surgery is required as shown by this commercial case-study. http://www.japaneseknotweedireland.com/case-study-1

Disposing of the "dead" remnants is also a problem (Like a "dead" snake, not to be trusted!). Complicated berms need to be constructed and the plant remains buried on an impervious sheet and soaked in even more herbicide.

So, just wondering what advice might be out there? I'm thinking fire! What would a Druid do?

Your experiences?

Yours aye,

Dathi

knotweed2.JPG (197.58 KiB) Viewed 798 times

[DaRC]

It looks like you have all the information currently available and there is no quick & easy cure that doesn't involve poisons & damage to the ecosystem.
The RHS say the same : http://apps.rhs.org.uk/advicesearch/profile.aspx?pid=218
I suspect this is like the bindweed in my garden - you have to be "on it". Make sure the rhizomes get no energy. Regular weeding to pull any new shoots, so they can't harvest energy from the sun. Careful digging to get the larger rhizomes out. This way all the energy in the rhizomes is put into sending up new shoots which are destroyed. Gradually, year by year, they get weaker.
Create a firepit where you can burn all the weed that you dig and pull out.

It will take years of constant attention - a bit like druidry really.

[Erithe]

We have a lot of that in our back yard (not at our current house, fortunately) and had to be really conscientious in removing it and making sure it didn't come back. You have very accurate information, as far as I can tell, and I agree with DarC - if you don't want to harm the environment nearby with chemicals, you'll have to haunt that location for a while and keep after it till it is well and truly gone.

Also, there are some uses for Knotweed:

Bee Hotel - http://www.gardenersworld.com/how-to/pr ... l/165.html
Quiche (apparently it's edible): http://kitchenvignettes.blogspot.com/20 ... uiche.html
Flutes, fiber weaving, & wine: http://www.ehow.com/list_6192340_japane ... rafts.html

So, once you've uprooted and killed it, there might be some uses for it (though I think you need fresh shoots to make the quiche).

I really like the bee hotel idea

[Corwen]

Glyphosate is the safest thing- I believe more powerful herbicides work better (24-D?) but kill everything else too, at least it is possible to apply glyphosate in a targeted way.

We had it at a Garden Centre I worked at, and even with the whole resources of the place and chemically trained people on hand to spray regularly we failed to eradicate it. The biggest problem was root fragments being transported around the site on boots and vehicle wheels (and probably taken to lots of other peoples gardens too on wheels and tools...).

Glyphosate, dig out, and burn.

[andromeda]

Japanese knotweed is an eddible and medicinal plant, there are many articles on line but here is one http://www.wildmanstevebrill.com/Plants ... tweed.html

I am yet to come across one but I read somewhere that a man had the same problem in his yard and managed to erradicate by eating it. Of course you have to be 100 pct sure it has no herbicides applied to it

[Dathi]

Greetings all, and thanks for the comments.

It looks like it is going to be a mix and match approach. A "war of attrition" seems like the only answer with cutting and burning along the river and (very) selective spraying away from the banks.

I might update this thread as work progresses.

I am aware of the edible and medicinal nature of knotweed. But it strikes me that you would have to have a heck of an appetite to eat your way out of a problem

I've also seen mention of knotweed being proposed as a biomass fuel (in the same way as Miscanthus) but I think that this would be an extremely foolhardy venture.

Yours aye,

Dathi

[Whitemane]

Glyphosate is the safest thing- I believe more powerful herbicides work better (24-D?) but kill everything else too, at least it is possible to apply glyphosate in a targeted way.

We had it at a Garden Centre I worked at, and even with the whole resources of the place and chemically trained people on hand to spray regularly we failed to eradicate it. The biggest problem was root fragments being transported around the site on boots and vehicle wheels (and probably taken to lots of other peoples gardens too on wheels and tools...).

Glyphosate, dig out, and burn.

Glyphosate is broken down very nicely by soil bacteria, as long as you have adequate rainfall. Under those conditions, it is non-persistent and safe for whatever is planted the following year. If it is too dry, the bacteria become metabolically inactive.

If you run into a dry spell, you may find it necessary to water the stuff you're trying to kill just to make sure the glyphosate is broken down.

[Rem]

Do let us know how it works out. Having worked as a field Ecologist in the past for a while I have come across it before. Especially with a cursing colleague who went to his allotment after work with the same boots...he was lucky though and did not take any rhizomes home that day.

The information here is solid so I won't add additional links with the same information.
All because it looked so pretty to the plant hunters. -_-