Control of Japanese Knotweed

[MartinD]

Although I've owned the woodland for over 18 months, I was horrified recently to discover a patch of japanese knotweed - how had I missed it!

Because it is close to a stream, I've spoken to the environment agency, and I've applied for a certificate to use 'Roundup'. However, the knotweed is within a hedge, and close to trees and ground plants.

Has anyone else had experience of this plant? It covers a small area - about 20 clumps within an area about 8 metres wide, and 2 metres either side of the hedge. I was thinking that if I cut it back on a fortnightly basis it may eventually run out of steam and die back without the need to apply chemicals - or is that a forlorn hope? (I'm aware that I need to handle the 'cuttings' with care, and burn them on-site. Unfortunately the farmer 'flailed' this hedge last autumn, and I suspect that I might find new bits growing as the season progresses.)

If I use chemicals I will probably kill some of the hedge in the processs, and there may be other casualties on the ground.

[RichardKing]

I have read elsewhere that the answer is to inject concentrated Glyphosate directly into the hollow stem using a syringe with a large diameter needle.

You can buy undiluted Glyphosate on Ebay.

[woodbodger]

I don't know why everyone gets so excited about Glyphosate, it's a chemical like water. Spray it on to the green bits of the plant, it is absorbed into the plants and they die, if you are worried about other plants in the immediate vicinity paint it on with a brush, stroke it on with cotton gloves ( worn over rubber gloves) or as you suggest inject it into the cut stem. It is not taken in through the soil nor is it harmful to aquatic life. It is actually a naturally occurring substance and is not toxic in the recognised sense. Me I would spray it on to kill the knot weed and replant any collateral damage that occurs.

[RichardKing]

Injecting Glyphosate directly into the stems is more effective than painting it on & depending upon absorbtion.

Injecting is also more selective than spraying.

Also it will take more than a single spraying to kill Knotweed.

[The Barrowers]

I am led to believe 7 years is about the time scale of Knotweed weakening

[DaveTaz]

The RSPB use the injection method of control after many years battling against it. The stems have to be cut, removed and burned, then injected. Apparently it is the most efficient way of dealing with it

[RichardKing]

When you say "removed", remember that you will require a licence to "move" it anwhere.

[Stephen1]

Hi Martin

I think the size of patch you describe is still very managable! I honestly would forget trying to weaken it by repeated cutting and go straight to glyphosate.

Consider getting one of these;

http://www.molevalleyfarmers.com/mvf/store/products/phillips-ezigrip-125ml-drenchervaccinator

They're used for vacinating sheep. You put a hypodermic needle (21g x 5/8" is an ideal size)on the front and the tube from the back goes into the sealed bottle that you have your herbicide in.

Once you get going it's very quick and the syringe automatically fills up between shots. If you use glyphosate then because it's systemic (i.e. it moves through the plants tissues after applying spreading throughout the whole plant) you don't need to inject every stem (i usually do one in three) as they're joined underground by rhizomes - so glyphosate passes between them.

Don't be tempted to make the herbicide mix up extra strong - follow the suggestions on the packet - if you make it extra strong then it damages the cells that it comes into direct contact with very rapidly, and is not then translocated out of these cells and into the plant as a whole. So instead of destroying the plants cells from the roots to the tips it only kills the cells that came into direct contact with it.

Jap. Knotweed has a pretty waxy cuticle which makes absorption of glyphosate difficult (particularly inside the hollow stems) I would recommend using glyphosate biactive which has other chemicals added that make the glyphosate more readily absorbed through the waxy cuticle.

The reality is though that even if you do everything right it's not going to be cleared up completely with one application and in one season.

Good Luck

Stephen