Japanese knotweed and Roundup stump killer.

Japanese knotweed and Roundup stump killer.

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Wacky Racer

Original Poster:

38,099 posts

246 months

Friday 27th May 2016
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Ok,

Have a problem with some of this stuff in the far corner of my (large) back garden, it is not a big area and comprises of 25 stems at most. I have done some research on the net and Youtube, and Roundup maximum strength stump killer seems the way to go.

I have treated the leaves with TWICE the recommended strength, and intend to keep doing it every couple of days for a week or so, to make sure it has the desired affect.

Apparently you see results in about three weeks, so I bought three packets to be on the safe side.

Two questions:-

The stems are now about a metre high, am I better just cutting the stem about a foot up and just pouring the stuff down the hollow stems, rather than on the leaves?

Also, any recommendations for buying a small bulk supply of the main ingredient glyphosate?

moles

1,794 posts

243 months

Friday 27th May 2016
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Gallup 360 is what I use about £25 for 5 litres mix up 26ml per litre of water. Don't up the concentration as it makes it less effective. It works by the plant ingesting it and destroying it from inside I think so you want it to get into the roots. If you up the dose it can simply burn the leaves off without attacking the inner part of the plant. Simpo will probably be along to explain it better

moles

1,794 posts

243 months

Friday 27th May 2016
quotequote all
That's the dose I use in a sprayer and it works a treat I would imagine it to work better with the leaves still attached and the plant growing as it should contaminate the whole plant.

Mandat

3,878 posts

237 months

Friday 27th May 2016
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I don't know about the actual treatment side, but what are you going to do with the rest of the cut stems?

tokyo_mb

432 posts

216 months

Friday 27th May 2016
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Spray the leaves now with the recommended dose. You want the glyphosate transferred down into the rhizome which is where the knotweed stores its energy. That should kill off the current stems, and lead to some weedier regrowth.

In the autumn when the knotweed is flowering inject 2-3ml of neat glyphosate into the stems one-two knots up from the ground.

Repeat for 2-3 years.

I had a similar size stand two years ago, am now down to two weedy stems this year, and hope to kill it off after another year of the same.

Edited by tokyo_mb on Friday 27th May 13:28

Equus

16,767 posts

100 months

Friday 27th May 2016
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Mandat said:
I don't know about the actual treatment side, but what are you going to do with the rest of the cut stems?
This.

And if you're cutting them, be careful that you don't inadvertently spread or carry fragments elsewhere in the garden: the conventional wisdom is that you only need a fragment a couple of millimetres long for a plant to regenerate from.

tokyo_mb

432 posts

216 months

Friday 27th May 2016
quotequote all
Wacky Racer said:
I have treated the leaves with TWICE the recommended strength, and intend to keep doing it every couple of days for a week or so, to make sure it has the desired affect.

Apparently you see results in about three weeks, so I bought three packets to be on the safe side.
You don't want to keep applying the glyphosate (or applying it at too high a rate), as doing so will just burn the leaves and they will drop off. Glyphosate works by being transferred down to the roots and killing the plant from there. That's why it takes a couple of weeks to see any effect. If you have destroyed the leaves the plant will no longer be transferring the food/energy it has created by photosynthesis down to the roots (technically a rhizome in the case of knotweed) and therefore you will not actually be doing any harm to the part of the plant you want to kill.

Wacky Racer

Original Poster:

38,099 posts

246 months

Friday 27th May 2016
quotequote all
Equus said:
Mandat said:
I don't know about the actual treatment side, but what are you going to do with the rest of the cut stems?
This.

And if you're cutting them, be careful that you don't inadvertently spread or carry fragments elsewhere in the garden: the conventional wisdom is that you only need a fragment a couple of millimetres long for a plant to regenerate from.
I haven't actually cut them yet, and don't think I will following the above advice, but will ring my local council for advice when/if I do.

Wacky Racer

Original Poster:

38,099 posts

246 months

Friday 27th May 2016
quotequote all
tokyo_mb said:
ou don't want to keep applying the glyphosate (or applying it at too high a rate), as doing so will just burn the leaves and they will drop off. Glyphosate works by being transferred down to the roots and killing the plant from there. That's why it takes a couple of weeks to see any effect. If you have destroyed the leaves the plant will no longer be transferring the food/energy it has created by photosynthesis down to the roots (technically a rhizome in the case of knotweed) and therefore you will not actually be doing any harm to the part of the plant you want to kill.
OK, thanks for that. Correct dosage in future.


Rangeroverover

1,522 posts

110 months

Friday 27th May 2016
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DO NOT let any authority of any sort know you have knotweed, your property and those within 50m will be unmortgageable

Wacky Racer

Original Poster:

38,099 posts

246 months

Friday 27th May 2016
quotequote all
Rangeroverover said:
DO NOT let any authority of any sort know you have knotweed, your property and those within 50m will be unmortgageable
OK, noted, but my property stands alone with no houses nearby and this stuff is in the corner of the garden 300 mtrs from the house.

I want to nip it in the bud so to speak. I understand it might be a three or four year job to eradicate it reading the net.

dave_s13

13,813 posts

268 months

Friday 27th May 2016
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Would it be worth getting a mini-digger in and excavating the stuff up and out in one fell swoop??

If it's only a small patch then a skips worth might get rid of it all.

battered

4,088 posts

146 months

Friday 27th May 2016
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You aren't allowed to put the stuff in skips. Any trimmings are to be burnt.

Wacky Racer

Original Poster:

38,099 posts

246 months

Friday 27th May 2016
quotequote all
dave_s13 said:
Would it be worth getting a mini-digger in and excavating the stuff up and out in one fell swoop??

If it's only a small patch then a skips worth might get rid of it all.
Not really, as I said it's only about twenty stems not very tall, but anyhow access would be a problem.

Thanks anyway Dave.

So, the main thing I have learnt is don't overdo the concentration, and make sure it doesn't spread.

Thanks for all the helpful replies.

Appreciated.

anonymous-user

53 months

Friday 27th May 2016
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if it is only a small amount like that, is there any sense in digging it up and burning it on the spot (i.e. without moving it)?

get a nice fire going in an empty drum or something and put the lot in there, stems, all the rhizomes you can dig up and maybe even the soil

Simpo Two

85,147 posts

264 months

Friday 27th May 2016
quotequote all
moles said:
Gallup 360 is what I use about £25 for 5 litres mix up 26ml per litre of water. Don't up the concentration as it makes it less effective. It works by the plant ingesting it and destroying it from inside I think so you want it to get into the roots. If you up the dose it can simply burn the leaves off without attacking the inner part of the plant. Simpo will probably be along to explain it better
Heh, honorary plant boff smile

I can't add anything to what's been said already. The main thing is that glyphosate isn't a direct killer, like fire or nitric acid, it works with the plant, so sympathy with/knowledge of how plants work is important. Spray the leaves to run-off, repeat at 7-10 day intervals especially on any new leaves, be patient.

herewego

8,814 posts

212 months

Friday 27th May 2016
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Maybe build a fire on top of it. Often.

LJTS

331 posts

182 months

Friday 27th May 2016
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I used to have loads of Japanese Knotweed in the garden and used Clinic Ace every time it appeared and now it's all gone!

Clinic Ace is nasty stuff but the best I've found for doing the job

Google it!

bobtail4x4

3,701 posts

108 months

Friday 27th May 2016
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Knotweed has waxy leaves, they just shed most sprays, as said you need to inject into the stems,
and repeat each year until they are gone,

dont dig it up and pass it to someone else, and FFS DONT tell the council.

Simpo Two

85,147 posts

264 months

Friday 27th May 2016
quotequote all
bobtail4x4 said:
Knotweed has waxy leaves, they just shed most sprays, as said you need to inject into the stems, and repeat each year until they are gone
Formulations should have wetting agents to help with this, but yes, waxy leaves and hairs all help to reduce efficacy.