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I think I've just found Japanese Knotweed - help!

(22 Posts)
FlopemOut Mon 06-Jun-11 21:56:17

I just went for a walk in our totally overgrown field (going to clear it this Autumn) and think I've found Japanese Knotweed. I understand it's incredibly invasive so am keen to hear suggestions on how best to get rid of it to ensure it's gone? I feel really depressed about the thought of a long battle with it, when I've got oh so much to do out in the garden already.

1973magpie Mon 06-Jun-11 22:25:07

We have it in our garden - I was not pleased when I discovered it as it's such an invasive weed angry.

We had an expert removal firm in to have a look to see what was best to do, and they recommended a three year treatment plan.

This involved cutting the stems down to just above ground level (laying them out on the concrete driveway until dry then burning them), and injecting the stems with weedkiller (picloram?). this would need doing in the next few weeks, and again (if necessary) in September-time. The September treatment makes sense as the plant is going into it's dormant winter stage around then, so the weedkiller should be taken down to the rhizome more.

This process would be repeated each year for two-three years until it was eradicated.

Unfortunately we can't afford to pay them to do it at the moment sad, so are going to have a go ourselves (I used to deal with knotweed at work a few years ago, so sort of know what I'm doing...)

FlopemOut Mon 06-Jun-11 22:28:09

thanks magpie - when you say 'inject' the stems- how exactly would you do that?

1973magpie Mon 06-Jun-11 23:16:04

We're still in the 'planning' stages so bear with me!

I thought we could get a large syringe (dh has some plastic ones with a pointed end, so no needle) fill it with the weedkiller and then you have to stick it in the top of the cut stem (when you cut it it is a bit like bamboo with the nodes, so you would need to push through the dividing bit between the nodes iyswim?) HTH

I think you can get injection guns from the US but they seem very expensive and hard to get hold of. Will have to google some more...

Sorry am crap at explaning, it's a good job I'm not a teacher...

chixinthestix Mon 06-Jun-11 23:33:34

You can pour the weedkiller into the cut stems with a jug or one of those cheap little houseplant watering cans with a nice thin spout. Make sure you cut the stems off just below a node so there is a big enough space to hold a decent amount. If you add dye to the weedkiller you will know which you have done. DH uses blue food colouring to be sure he hasn't missed any stems.

Late summer treatment is much more effective than spring - wait until it flowers in Aug/Sept as magpie says, and then spot treat the regrowth that comes up the following spring. After 3+ years of treatment on some of the areas I look after for work it has all but gone, but the odd stem still comes back.

If its a really big clump then I'd really recommend getting a contractor in or contacting your council. Ours did offer treatment of knotweed on private land for a charge - not sure if they still do now. They will be able to use commercial weedkillers at stonger concentrations than the stuff you can get at the garden centre, so likely to be more effective.

FlopemOut Tue 07-Jun-11 10:59:29

You know the more I look at these few stems of weed, the more I think perhaps they are something else. I can't find anything decent on the internet to help me ID them. I think I might phone an expert to see if we can get them surveyed so that we know exactly what we are dealing with. The plan was to clear, rotavate and seed the field in the autumn but we obviously don't want to do that if it is Knotweed as we'll spread it everywhere!

chixinthestix Tue 07-Jun-11 22:12:17

Can you post a pic Flopem?

Roflharris79 Wed 08-Jun-11 13:25:17

It might sound silly, but if it is indeed Japanese knotweed, have you thought about trying to co-exsit with it, rather than battling it.

I have never had the pleasure, but I've heard that young knotweed stalks have some culinary use, very similar in taste and prep methods to rhubarb.

Obviously confirm the plant's id and d.y.o.r first.

FlopemOut Thu 09-Jun-11 13:26:32

My husband says they are definitely not Knotweed and having looked at so many photos, I now agree. Phew I can sleep tonight. Must admit however they are a very strange weed I've not seen before.

whatatip Fri 10-Jun-11 18:32:38

Can you post a pic nonetheless? I am intrigued now.

FlopemOut Fri 17-Jun-11 07:32:04

I would do except for the fact that my husband chopped them down on the basis that whatever seeds were developing on this weed, he didn't want it spreading. If they reappear I will report back.

frostyfingers Tue 21-Jun-11 09:13:07

I know you think it isn't knotweed, but I vaguely remember somewhere that you had to report its presence as it is such an invasive plant - Defra or Natural England I think.

1973magpie Wed 22-Jun-11 21:07:02

It's not a reportable weed (like Ragwort etc) any more, it's known as an 'Injurious weed' (current info. from DEFRA/English Nature), they don't seem that bothered about it on private residential property to be honest, it seems to be taken much more seriously on commercial development sites!


1973magpie Wed 22-Jun-11 21:09:52

Also, for anyone looking to treat knotweed at home - Roundup Stump killer is available at Garden Centres and is much stronger than the normal Roundup as you mix it up yourself - it even has instructions on the packet to tell you how to use it to treat knotweed HTH

BikeRunSki Wed 22-Jun-11 21:17:39

Japanese Knotweed

Japanese knotweed advice etc is from the Environment Agency (I work for them), who are part of the Defra "family". It is not an offence to have it on your land, but it is an offence to spread it. It is very easy to spread it, ie: on the soles of your boots etc - the spores live for ages.

queenmaeve Thu 23-Jun-11 22:17:29

my sister had a mortage refused as it was discovered on a property she was buying.

echt Mon 04-Jul-11 19:11:49

Assuming that what you've got IS Japanese knotweed, you can eat it. Just google for recipes. Disclaimer; I have never tried these recipes.grin

CJCregg Thu 07-Jul-11 18:27:03

Absolutely DESPERATE for knotweed advice ...

I am about to exchange on a house and the surveyor has found knotweed coming through from neighbouring land. Do anybody know what I should do next? Apparently I'm lucky to have had my mortgage offer (it wasn't picked up on their valuation survey) and its continued presence could affect any future sale of the house.

I'm not even sure if it's the vendor's responsibility, as it's coming through/under the fence from neighbouring land. This is an area where the road next door park their cars, so I'm not sure who owns it.

I am really panicking here. Can anybody help?


windrushbreeze Thu 13-Oct-11 15:31:17

Message deleted by Mumsnet.

Toni1982 Thu 31-May-18 20:13:01


Sorry to hear about Japanese Knotweed, it's really tricky to get rid of.

I recently wrote an article about what it looks like during different times of the year, the history of it and how to eradicate it etc. Have a read, it might give you a bit more of an understanding of it

Hoopaloop Thu 31-May-18 22:24:55

You don't have to report ragwort either.

If you have knotweed (post pics to confirm), Roundup Biactive was labelled to deal with it. JKN should not be tall at the moment. You should be able to spray the foliage and get reasonable results. You will not kill it in one go. You will have to keep hitting it each time it sends up green leaves. This will happen for more than a year.

Hoopaloop Thu 31-May-18 22:28:29

Matey who has JKN on their land is responsible for any damages arising from it spreading to neighbouring land. You will need a joined up approach to get all affected to treat it as of one person avoids this it will carry on. JKN wouldn't necessarily put me off. But then again, I've dealt with it before and have think it's management is often blown out of proportion.

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