Over the last decade, Japanese knotweed has developed a reputation for being one of the most aggressive, invasive plants to be currently blighting the country. However, despite the plant’s fearsome reputation, there can still be some confusion as to what it actually does. This article will explain what Japanese knotweed does from two perspectives: environmental and financial. The examples cited here should be considered within the larger context of Japanese knotweed cases, this plant can thrive in all sorts of environments, but no single infestation is the same.

What are the environmental impacts of Japanese knotweed?

Japanese knotweed has a number of physical characteristics which has made it particularly troublesome in the UK, chief of these is the incredible speed that it grows at. Whilst it does die back during winter, its peak growth during the summer can see it growing up to 20cm a day and 1.5 metres in the space of a week. Coupled with its incredible resilience, it’s unsurprising that the government has labelled Japanese knotweed as an invasive threat

Not only does Japanese knotweed grow fast, but it also spreads at an alarming rate. Although the plant does not propagate in the usual fashion in the UK (only the female of the species was imported to Britain in the 19th century), it spreads via an underground root system, comprised of rhizomes. Not only are these roots fast-growing, but they’re also capable of growing from the smallest of fragments, which was one of the driving factors behind the government making it a criminal offence to move soil that has been contaminated with the plant.

Unfortunately, despite the control measures that have been put in place, the spread of Japanese knotweed has continued to the point where the plant is estimated to an infestation for every 10 square kilometres in Britain, according to PlantTracker who produced data that helped build a map showing the spread of Japanese knotweed in the UK.

How deep are Japanese knotweed roots?

Japanese knotweed roots can develop a system that burrows up to 3 metres deep underground and a further 7 metres horizontally from where the plant breaks ground. The depth and complexity of this root system make it a difficult and costly task to remove completely. Whilst digging out the plant is considered to be one of the most effective methods of eradicating Japanese knotweed, the cost and disruption of doing so can be prohibitive to some.

Does Japanese knotweed smell?

Japanese knotweed does not have a particularly distinctive smell. Its scent is not considered to be one of its defining features and does not contribute to its undesirable reputation.

Is Japanese knotweed dangerous?

Japanese knotweed is not poisonous, nor does it pose any physical danger to animals or people. The plant does, however, pose a threat to native plants that are not as well equipped to compete with this foreign element. The environmental impact that this plant has on our own wildlife is often overlooked in favour of the financial costs of treating it. When the plant is allowed to thrive on public waterways or on disused industrial lots, it can quickly stifle the growth of any other plants growing nearby.

What are the financial impacts of Japanese knotweed

Setting aside the environmental impact of this invasive species,  an infestation can have serious financial implications for all involved. Homeowners discovering Japanese knotweed are faced with the knowledge that the value of their home will almost definitely depreciate. Developers who want to build on land with Japanese knotweed may have to completely redraw their plans, as they might have to pay for the complete removal of the infestation before they can go ahead with any construction. For example, plans for developments, in the lead up to the London 2012 Olympics, were delayed when a massive infestation was discovered on the proposed land. Teams spent four years getting the weed under control.

Perhaps most frustratingly, Japanese knotweed infestations can lead to wasted time and the collapse of property chains, which come with their own set of financial pitfalls. For example, often a prospective buyer may spend hundreds of pounds on surveying a property, under the impression that there is no Japanese knotweed present (according to the TA6 property form). On discovering a significant infestation and not wishing to take on the responsibility that comes with treating it, the buyer may drop out of the purchase, but there will be no legal recourse for them to recover the money that they spent on the survey as no form contract would have been signed.

All told, Japanese knotweed is estimated to cost the UK economy £166 million per year for treatment and in property devaluations.

What does Japanese knotweed do to a house?

Japanese knotweed does not necessarily ‘write off’ a house. How the plant affects the property will depend on the severity of the infestation and how close the plants are to the buildings. Although it’s possible to find evidence of Japanese knotweed literally breaking through into homes, this is rare and usually the result of a combination of poor building maintenance and a particularly aggressive infestation. Japanese knotweed’s predominant effect on a house is financial. In the average case of Japanese knotweed discoveries, the value of the property is diminished between 5-20%.

Can Japanese knotweed grow through concrete?

There is some photographic evidence to prove that Japanese knotweed can grow through concrete, however, this has only been noted to happen in scenarios where the infestation is particularly bad and the construction work is particularly shoddy. In extreme cases, Japanese knotweed is also know to disrupt independent structures such as garden sheds, greenhouses, fences. The plant can also slowly break through shoddy brickwork, paving and tarmac.

Can Japanese knotweed damage foundations?

It’s possible for Japanese knotweed to damage the foundations of a house, but this will only happen when infestations are long-established and there are already weaknesses in the building. In very rare cases, Japanese knotweed has been known to break its way through floorboards and skirting boards which can lead to a house being unsellable, as in the case of the Joneses in Broxbourne who were recommended to demolish their entire home. Their property’s value plummeted from £350,000 to £50,000 – a rare example but one which has had an impact on the industry at large.

Can you sell a house with Japanese knotweed?

It is legal to sell a house with Japanese knotweed, however, the invasive plant’s reputation often makes it difficult to sell up when the time comes to it. If you’re attempting to sell a property with Japanese knotweed then you should state that the property has been affected on the TA6 property form. Similarly, if you’re aware that the land has been treated at some point, even if the knotweed has died off, you should still mention it. Failing to mention or lying about your property being affected by Japanese knotweed could lead to a misrepresentation claim being brought against you.

Can you get a mortgage on a property with Japanese knotweed?

You can get a mortgage on a property with Japanese knotweed, but most mortgage lenders will first ask to see evidence of a knotweed management plan being in place. This plan will prove that you have hired a PCA-accredited removal firm to manage the removal of the plant, and will also be insurance backed, so that in the event that the firm goes out of business before the plan is complete, another company will carry on the work. Although some lenders have relaxed their stance on Japanese knotweed, there are some that still refuse to give mortgages for properties affected by it. Re-mortgaging properties that have recently become infested can also be difficult, depending on the lender that you’re dealing with.

Finally, a Japanese knotweed infestation can also be the root of tension and conflict between two parties, whether they’re neighbours, or strangers attempting to negotiate a sale. Due to the potential legal complications that can ensue from the discovery of Japanese knotweed, the plant can also be responsible for undue stress and pressure as individuals attempt to fight their corner without the legal help that they need to succeed. Without legal aid, parties can quickly become trapped in a frustrating back and forth with councils or organisations, this time wasted can only add to the pressure as both parties are aware that whilst the discussion is ongoing, the infestation is being allowed to continue growing.

If you’ve discovered Japanese knotweed on your land, or are currently locked in a dispute related to it, then we may be able to help. Give us a call or send us a message using the contact form, and we’ll get back to you with guidance on how best to proceed

Freephone 03335 777 888

The internet is filled with masses of information regarding Japanese Knotweed, and some of it can be particularly frightening. We receive dozens of phone calls every day, and many people as us to debunk myths that they have read online. Here are some of the most common, and why they are incorrect.

“You kill Japanese Knotweed by cutting it down and pouring bleach into it”

There are many different versions of this one using various different substances, but the answer to them all is no. The only substance we know to kill Japanese Knotweed is a glyphosate-based herbicide. Unfortunately, the herbicides which are available to the public are also not strong enough to do the job. The herbicide experts will use is 300x stronger than anything available for purchase by the public.

“You cannot get a mortgage on a property if it has Japanese Knotweed”

We receive many panicked telephone calls from people on both sides of the purchase who believe this to be true, but worry not, because we can help. We can support your enquiry with a Site Survey and Management Plan by an accredited firm, coupled with an insurance backed guarantee. If you have these documents in place from an accredited company, mortgage lenders will typically release the funds.

“Japanese Knotweed can break through concrete”

There are many horror stories littered across the internet regarding Japanese Knotweed, often about its strength and the damage it is capable of doing. Japanese Knotweed cannot break through a solid piece of concrete in a normal way. It will, however, seek out any cracks or weaknesses in any structure, and many properties will have small cracks or movements below ground caused by various things including subsidence and foundation settling. Like all plants, Japanese Knotweed seeks light when underground. Its rapid growth means that a small piece could find its way through a crack, and then push it open as it grows.

Japanese Knotweed is not a superhero, but should still be taken seriously.

Japanese Knotweed growing on a property based in Bristol has been the cause of a property firm being indicted with a hefty fine. The Japanese Knotweed affected 7 properties and Bristol City Council prosecuted MB Estate Limited which owned the offending property.

The presence of the Japanese Knotweed was not highlighted in house surveys undertaken by the owners of the affected properties, even though the plant was thought to be reaching 8 foot. Unfortunately for the buyers, they were unaware of the adverse effects Japanese Knotweed could cause on their properties and it was only when one homeowner Googled the plant that the severity of the situation became clear.

When the Anti-Social Behaviour, Crime and Policing Act 2014 came into effect, it was only then the local council were able to take action against the property management firm. The firm had various opportunities to take steps to remediate the invasive weed and unfortunately did not take adequate steps to prevent the legal action to be taken against them.

With cases such as Waistell v Network Rail making headlines recently, it has set a precedent for other homeowners who are affected by the troublesome weed that there are cautions in place to ensure encroachment does not occur, and where it does, redress through legal channels is now available.

Getting lost in the legal jargon which is thrown at you once you instruct a legal professional is a rabbit hole too many of us take a trip down, make sure you know what a Part 35 report is and when you might need one.

Generally, Japanese Knotweed disputes are easily resolved once an individual takes responsibility for the presence of the weed and ensures that it is eradicated in line with the specific rules and regulations put in place. However, in some circumstances where the origin of the Japanese Knotweed is harder to determine, or in situations where the landowner is denying liability, you may need to consult your solicitors on the best way to proceed down the legal route.

Japanese Knotweed is classed as a ‘Schedule 9’ plant and in relation to this, Section 14(2) of the Wildlife and Countryside Act 1981 states that “if any person plants or otherwise cause to grow in the wild any plant which is included in Part 2 of Schedule 9, he shall be guilty of an offence”. Due to this, we see time and time again, instances where individuals have taken legal action against landowners who have allowed this highly invasive weed to encroach onto their sites.

Typically, your solicitors will firstly arrange for an initial vetting report which will give them the basic details of the Japanese Knotweed they will need to know before being able to decide as to whether or not the case can be taken to court. Once they have the initial vetting report, this is usually when solicitors will arrange for the P35 Report.

Part 35 Compliant Reports are specific documents which answer the questions solicitors will need to know and use in their court case. Typically, these P35 reports are used to determine the cause of the origin of the Japanese Knotweed and therefore pin liability to the correct person. P35 Reports are usually taken around a week to compose due to the in-depth analysis required to fully investigate the situation at hand. If you are not proceeding down the legal route, you usually won’t require this service.

It is important to know that the Part 35 writer has a duty to the Court and not to the person paying for or requesting the report. A Part 35 report writer will know that their duty of being correct is to the court and anything other can be seen as contempt of court.