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Japanese knotweed

(22 Posts)
bananaskin123 Tue 21-Apr-15 12:13:42

Yes, we have discovered this. We have a large garden with grass but in what we call "the wilderness" is lots and lots of the dreaded JK. My DH noticed it a long time ago but didn't tell me as he didn't want to worry me! Meanwhile he has been strimming it down which, looking on line, is the worse thing to do as it spreads it. Our occasional gardener is offering to treat it by injection but has to wait until it flowers in May. Not sure he realises how much is there but he's coming to have a look this evening.
What I was asking is has anyone had theirs treated by a company and roughly what the cost is. I've looked on Youtube and spraying and injecting seems to be the treatment although there are also videos of diggers and lorries removing the soil but hope this might be more for building sites as I am sure that would be very expensive. Luckily its about 70 ft from the actual house.
Anyone have any advice they can offer.

shovetheholly Tue 21-Apr-15 13:27:38

Oh gosh, I'm so sorry. flowers <- non-Japanese knotweed flowers for you.

It sounds like you're doing the right thing - getting on top of it before it gets worse and creeps towards the house is vital. I have no personal experience but I hear that digging doesn't really work and that spraying/injection is the way to do. Make sure that you keep well out of the way when it's happening - the stuff they will put on is not good for your health!

The other thing I wanted to say is to brace yourself - it will be expensive - and to make sure that you really trust the people doing it. In my area, there are lots of cowboys who sound really cheap, but don't actually get rid of it. You need someone who is really going to go to town on it.

TheFnozwhowasmirage Wed 22-Apr-15 22:35:47

I've gotten rid of it in 3 different gardens successfully and the stuff I've used is no more toxic than over the counter weed killer. You need Roundup Bioactive,and you may need to go to a farm suppliers to get it. Apply in April/May by spraying on the new growth. Then,in September, do the same thing. It is important you don't forget because that is when the plant takes energy down to it's rhizomes for the winter,you want it to take the weed killer down too. Next spring,the knotweed may come up looking different,don't be fooled,same routine again for up to 3 years,until it doesn't come up again. If I remember rightly,the solution is 1 part round up to 3 parts water,but it will tell you on the container. If you need any more help,pm me.

Wiifitmama Wed 22-Apr-15 22:38:45

We discovered it in our garden when we moved in 6 years ago. Also about 70ft from house. I was in a panic after reading online. In the end, we just pulled up the little shoots every time we saw them. Actually, got the kids to do it! We were fairly vigilant for a couple of year. Rarely see a shoot now. We did not use chemicals.

Qwebec Fri 24-Apr-15 02:00:55

I'll repost here

Ok, the easy way not fight involved. Bring the bamboo down to ground level. Cover the "contaminated" area with a black plastic (or what ever cuts the light supply). Wait 2 years. Everything will be dead.

Qwebec Fri 24-Apr-15 02:02:49

That's what my city does to get rid of it. Plant tall and full plants in front of the tomb to hide it.

EcclefechanTart Fri 24-Apr-15 15:42:46

That method did not work at all for us, Qwebec. The previous owners of our house built a patio over the knotweed, with a layer of plastic under it. It still came up!

What seems to have worked for us is cutting off the stems and injecting the hollow middles of the stalks with glyphosate weed killer, via a smallish syringe. This took action much quicker than spraying the leaves and is easier to target just the knotweed without any spray drift.

It has taken us three years of doing this fortnightly during the growing seasons, but we seem at last to be free of it.

EcclefechanTart Fri 24-Apr-15 15:44:46

Meant to add, we've done this ourselves, not paid someone. A lot less came back the second year and the third year hardly any. We,re in the fourth year know and there seems to be none left.

Polyethyl Fri 24-Apr-15 16:09:42

We did the cut and cover with tarpaulin method. It took several years. We now have a beautiful lawn. But occasionally a sprout pops up which we pull out.

Qwebec Sun 26-Apr-15 03:10:21

I have no idea why it did not work with yours. But there has to be absolutely no light coming in.
this is in the UK, they only did it for 15 months and the plastic teared at places, but 90% of the pest was eradicated.
And as I said the city has been using this tactic successfully since years in natural places where they can't use chemicals.

the mysteries of nature confused

shovetheholly Mon 27-Apr-15 16:28:05

This is intriguing.

I know people who swear they have got rid of knotweed by covering it, and others who swear equally adamantly that theirs is punching through the covering. I believe both!

I wonder whether it grows more vigorously in some areas than others, or whether there are some genetic variants that are more difficult to kill?

jilted Mon 27-Apr-15 20:29:58

We've just discovered we have it in our rented property. Hoping gardener can deal with it as we can't get up there very soon. I've red awful stuff about people not getting mortgagees and it growing through floors ect. We are planning to sell soon.
Any more advice appreciated. Sorry for jumping on your thread op, I was just about to write my own!

jilted Mon 27-Apr-15 20:31:45

Does this mean we won't be able to sell anytime soon?

Fairylea Mon 27-Apr-15 20:33:46

We had some in our front garden. Dh was able to dig very deep and pulled it up by the root and then we poured industrial strength weedkiller down the hole. That was several years ago now and it hasn't come back. I guess a lot depends on how extensive it is.

shovetheholly Tue 28-Apr-15 07:56:08

Jilted - I think it depends on the mortgage provider's T&Cs. They used to say no a lot, but there were some stories in the press saying they've loosened up a bit owing to the fact that they are realising that this is a nuisance but not an actual murderous triffid about to wipe out entire human villages. Maybe post in the property forum about this, if you haven't already?

I would take a nuclear approach, i.e. make sure your gardener is dealing with it properly, and not just strimming it or something like that (as the OP's DH did!).

MACCA3 Fri 01-May-15 14:06:18

We found JK last year when about to sell. Very close to house so worst place it could be but v small amount. You have to declare it to any buyer. On the SPIF. Banks will only lend with a treatment plan in place i.e. herbicide or excavation. We excavated - has to be done by a professional Jk co. Much stress, much money but it has now gone. There is a lot of scaremongering and worry. If anyone needs info let me know. I found myself, sadly, a bit of an expert due to what happened to us. Would be happy to help anyone as it is a worrying time.

CruCru Sun 03-May-15 09:46:48

Does it look like this? I was in the park the other day and noticed this plant had come through the Tarmac - wondered if that was japanese knotweed.

MACCA3 Sun 03-May-15 21:29:51

It's hard to say from the pic. JK has heart shaped leaves and a thick bamboo like stem at the bottom. If it grows massively in the next few days it might be. It can grow 10cm a day in the growing season I.e. now!

taxi4ballet Mon 04-May-15 18:11:23

Friends of ours had a rented house and there was this stuff in the garden. As it wasn't their house they couldn't have cared less and did nothing to get rid of it.

Then, it came up through the floor in their lounge!!

TheFlyingFauxPas Sun 10-May-15 00:04:07

bloody hell taxi4ballet that is a bit triffidy!

IvoryMadonna Sun 10-May-15 13:15:26

I had it in a small front garden before most people had even heard of it. I certainly didn't know what it was, or what it could do - all I knew was that it was incredibly persistent and grew rapidly to vast proportions! Digging it out only seemed to encourage it.

I did manage to get rid of it with a glyphosate (think I used Tumbleweed). Every time any of it came back I hit it again, and after much vigilance it eventually failed to reappear. Good luck!

EcclefechanTart Sun 10-May-15 20:52:59

Triffids! This couple had to knock down their house because of the dreaded JK:

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