The Dangers of Japanese Knotweed

The Dangers of Japanese Knotweed

18:05 PM, 9th July 2018, About 6 years ago 5

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We have had a few Property118 readers questions on this subject in the past.

The Dangers of Japanese Knotweed

The dangers of Japanese knotweed have been thrown into light recently after a court ruling spurred discussion as to whether landowners can claim damages if the plant has spread to their property.

A Court of Appeal filed in favour of two homeowners from South Wales who sued Network Rail when knotweed from a railway embankment invaded their properties. But, is this opening the floodgates to more cases? Or is this just a small reminder of the dangers of this notorious plant and how much they can affect a property?

If you’re a homeowner looking for information, or a construction site manager looking to brush up your knowledge, Build-Zone have put together a small guide that tells you everything you need to know.

Why Does it Matter?

The plant, which originates in Japan, has become more out of control in the UK as we don’t have any natural predators to stop it spreading. This affects the construction industry massively because of its ability to damage concrete, buildings, tarmac and more. It has been known to block footpaths and constructions such as flood defences.

Because of its invasive nature, it is infamous for impeding the sale of buildings. The long-term effects can make many properties unsellable because the weed decreases its value. This can cause huge problems for builders, developers and homeowners alike.

What Are the Dangers?

There is a multitude of reasons why Japanese knotweed is dangerous, from the way it grows to how you get rid of it. Here are a few of the main ones:

It’s Rapid Growing

Japanese knotweed is the UK’s fastest-growing invasive weed. During its peak time in the summer months, it can spread by as much as 10cm a day. What may look like a small weed can suddenly become a huge problem if left to its own devices.

It has Large Root Systems

The reason why this plant can do so much damage is because it has such a wide-ranging root system. Growing metres in all directions, this plant can destroy the foundations of buildings and drains, if left to grow and spread.

It’s Difficult to Get Rid Of

Getting rid of this pesky plant is more difficult than you might think. It’s not simply a case of picking it out, because if care is not taken, trying to chop it down can cause it to re-grow fast. Proper treatment of the plant can take months and often needs to be surveyed and treated by professionals.

It’s Hard to Identify

Japanese knotweed has a few very distinctive features, but it can look similar to other plants. The plant has fairly large, heart-shaped green leaves that are around 10cm long. They also have bamboo-like stems and can grow flowers in late summer. However, like most other plants, they go brown and the leaves fall off.

It Affects Lenders

Most lenders will not offer financial loans for developments or properties that have Japanese knotweed or even a history of the plant. But, Build-Zone, as an extension of Sennocke, has negotiated a Lloyd’s Insurance Backed Guarantee facility, for Japanese knotweed. This brings a solution to developers and consumers for this major problem. Build-Zone is working with Japanese knotweed removal companies, who can guarantee removal for up to 10 years.

Editors Note:

The Ultimate Japanese Knotweed Guide –

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Ian Morgan

6:51 AM, 10th July 2018, About 6 years ago

Leeds University research has contradicted a lot about what we have been led to believe about this pesky plant! This link is well worth a look and may lead to changes. That's why I am sharing it here!

Chris @ Possession Friend

8:24 AM, 10th July 2018, About 6 years ago

Reply to the comment left by Ian Morgan at 10/07/2018 - 06:51
The Environment Agency state Japanese Knotweed is the most pervasive and dangerous species, There is a £5 k fine of 2 years in HMP's 'Travel Lodge' for spreading its waste.
( thinking about it, Most in HMP's accommodation don't even spend 2 years there, unfortunately 😉
If you pay anyone - Aecom enough, they'll say what you want to hear ! which I'm sure Network Rail did for their court of Appeal case.

Jan Martin

9:30 AM, 10th July 2018, About 6 years ago

Reply to the comment left by Ian Morgan at 10/07/2018 - 06:51
Read this last night Ian . Maybe this will stop a lot of people making a lot of money from this .

Michael Barnes

12:57 PM, 12th July 2018, About 6 years ago

Reply to the comment left by Ian Morgan at 10/07/2018 - 06:51Insufficient information in there to make a judgement; need to see the full paper. For instance, it does not give the maximum distance at which roots were found, just states "rarely greater than... And does not give quantitative statements of damage caused."
Whilst it says "less damage than other plants", it seems to me that the issue is "other plants are much easier to remove" and can often be removed by an amateur gardener.


19:16 PM, 16th July 2018, About 6 years ago

Reply to the comment left by Jan Martin at 10/07/2018 - 09:30
Nah - it's the vegetation equivalent of the Great Rising Damp Scandal. It's never going to go away.

We got caught out having to pay ££££ for a program of multiple visits to remove it in respect of a block in Scotland which we have a unit in a few years back.

It would have been a completely pointless waste of time trying to argue with the factor, so we just had to take it on the chin.

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