Japanes Knotweed

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Only through 'cracks' in concrete. Not through uncracked concrete!
Google images says otherwise.

Few answers your friend might find helpful from when I was talking to a knotweed specialist, his replies in red.

1: How big a risk is this? Will the property ever be truly knotweed free or is there always a possibility that it'll come back?

Reply - Unless of course you have an excavation conducted then the rhizome will remain in the soil and will always be considered contaminated soil. Even though you may not be seeing re-growth in years to come, it may be that the rhizome is in a dormant state. We would advise not disturbing the soil in the risk zone marked in the report

2: Are there cases where the treatment can actually completely eradicate the entire network and that's it, gone?

Reply - No. As above, the soil will still be considered contaminated even if you do not see re-growth. However, herbicide is very effective in stopping the spread of the rhizome in the soil.

3: How does Japanese Knotweed actually spread? I'm aware it was brought over by the Victorians but how has it spread across the country? Is it airborne via seeds or is it just cross contamination over time?

Reply - It is mainly spread by human interference by the rhizome (underground stems). People moving contaminated soil from one place to another for example. We only have the female plant here in the UK so it does not produce any viable seeds.

I really wanted the house but the fact we wouldn't ever be rid of it unless we paid roughly £10k to get it dug up, was enough for me to pull out.
 
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Only through 'cracks' in concrete. Not through uncracked concrete!

As the saying goes, theres only two types of concrete... cracked and waiting to crack. It only needs a tiny void and it will grow though and as it does so it crates larger cracks and then you have a serious problem.
 
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In pic1 everything green apart from the background trees looks like Knotweed. In pic2 it looks to be growing along the fence line up his neighbours garden.

While a management plan will knock down what pops up in his garden it just looks like a problem that will only get worse unless the neighbouring landowners make a concerted effort. I hope the price your friend paid reflects the fact that his future sale could be impacted.
 
Soldato
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In pic1 everything green apart from the background trees looks like Knotweed. In pic2 it looks to be growing along the fence line up his neighbours garden.

While a management plan will knock down what pops up in his garden it just looks like a problem that will only get worse unless the neighbouring landowners make a concerted effort. I hope the price your friend paid reflects the fact that his future sale could be impacted.

No, the knotweed is only behind the rear fence
 
Soldato
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Massive amounts of scaremongering and misinformation related to Japanese knotweed. It's not nearly as much of an issue as many would have you believe

What compels you to wade into a thread and subject that you clearly know lonely enough about to be dangerous, and spout ******** that could lead to someone making a terrible mistake?
 
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I've done my city & guilds PA1 & PA6 this year which means I can buy commercial chemicals & use a knapsack sprayer to spray commercially.
Does that make me a "knotweed specialist"...lol.
There is definatly a massive overkill industry around knotweed. Glyphosate will kill it like any other weed. Although commercial strength & adjuvant is best & it does take around 3 years to kill all.
Larger plants like in the Op's need may need stem injection which is another course again.

It was a fairly intense 3 day course, but if your fairly handy I'd recommend it for some, to circumnavigate a stupid quote.
Once you've done it, your deemed a proffesional.
 
Soldato
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I spoke to a long term landscape gardener yesterday who told me that there are much worse plants out there. Japanese knotweed has had the run of the press. Other plants that are just as bad if not worse!
 
Soldato
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I spoke to a long term landscape gardener yesterday who told me that there are much worse plants out there. Japanese knotweed has had the run of the press. Other plants that are just as bad if not worse!

I reckon that buddleia is one of said plants. I've seen that plant grow pretty much everywhere & it grows quickly too. Especially by railway lines.
 
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