The Consequences of Letting Japanese Knotweed Spread

Why are there consequences for letting Japanese Knotweed spread?

Japanese Knotweed grows quickly and its strong roots can create a destructive underground network undermining buildings and foundations, and potentially causing thousands of pounds of damage.

Beyond the physical damage, the spread of Japanese Knotweed can have serious financial and legal implications. It is often flagged during property surveys, leading to decreased property values and potential difficulties in securing mortgages unless professional treatment plans are in place

How quickly does knotweed spread?

Japanese Knotweed can grow up to ten cm per day, with roots growing out in a seven-metre radius, meaning it can quickly spread from one garden to another, infesting whole areas.

To see just how fast Japanese Knotweed spreads, here is a time-lapse video of Japanese Knotweed growth.

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Is Japanese Knotweed a notifiable plant?

Japanese Knotweed is a garden pest and it is the responsibility of the landowner to manage it. While it is an invasive plant and it is advisable to take action quickly to prevent it from spreading, there is no statutory requirement to control/eradicate or even report its presence.

It is, however, an offence, under the Wildlife and Countryside Act 1981, to plant or cause Japanese Knotweed to grow in the wild. This can be enforced by both the police and local authorities, and you may face a fine of £5,000 or even a prison sentence.

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The Most Common Consequences of Letting Japanese Knotweed Spread

There are a number of consequences that can arise from allowing Japanese knotweed to spread, and we have listed them out for you below:
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Structural Damage:

Japanese Knotweed’s underground rhizomes can grow up to 3 metres deep and spread laterally, exerting pressure on concrete, tarmac, and other materials. This can lead to cracks in foundations, driveways, walls, and drainage systems, compromising the integrity of buildings and infrastructure. Repairing such damage often involves excavation and rebuilding, which can be extremely costly.
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Decreased Property Value:

The presence of Japanese Knotweed is a red flag for potential buyers and surveyors, as it signals potential structural risks and management costs. Properties affected by Knotweed are often devalued or require significant price reductions to offset the perceived inconvenience and risk. In severe cases, properties may become unsellable until the issue is addressed.
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Mortgage and Lending Issues:

Many lenders are reluctant to approve mortgages on properties with Japanese Knotweed due to the potential risks and costs associated with its removal. To secure a mortgage, sellers often need to arrange a professional Knotweed management plan, which provides assurance that the plant is being controlled and will not cause further issues. This is something that should be offered by any good Japanese Knotweed removal service.
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Legal Consequences:

Allowing Japanese Knotweed to spread onto neighbouring land can result in legal disputes. Under the Wildlife and Countryside Act 1981, it is an offence to allow Knotweed to grow in the wild. Additionally, under the Anti-social Behaviour, Crime and Policing Act 2014, neighbours or local authorities can take action if the spread of Knotweed causes a nuisance, potentially leading to fines or mandatory remediation.
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Environmental Impact:

Japanese Knotweed is highly invasive, spreading rapidly and outcompeting native vegetation for resources such as light, water, and nutrients. This reduces biodiversity, disrupts local ecosystems, and threatens wildlife habitats. Its aggressive growth can also cause or speed up soil erosion in affected areas.
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Cost of Eradication:

Controlling Japanese Knotweed is expensive and labour-intensive. Professional treatment plans, which often include herbicide application or excavation, are usually required to ensure compliance with environmental regulations. Costs can run into thousands of pounds, especially if the plant has spread extensively or if legal issues are involved.
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Potential Fines or Compensation Claims:

Property owners can face legal penalties if they fail to manage Japanese Knotweed properly. Neighbours whose properties are affected by the spread of Knotweed can claim compensation for damages, and local authorities may impose fines or require immediate action to prevent further spread. This adds financial and reputational risks for individuals and businesses alike.

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The consequences of letting Japanese Knotweed spread - a case study

Homeowners whose properties become infected with Japanese Knotweed due to negligence by neighbours who let the weed spread will now be able to claim damages. This follows the case of Williams and Waistell v Network Rail. The two neighbours in Maesteg, South Wales, were awarded damages after the rail company failed to prevent the spread of the Japanese Knotweed onto their land.

Stephen Williams and Robin Waistell owned adjoining bungalows backing onto Network Rail property. Japanese Knotweed had been present on the rail company’s land for over fifty years, and the two had first complained about it in 2013.

In 2017, the pair won their case and were each awarded £4,320 to treat the Japanese Knotweed, plus a further sum of £10,000 to compensate them for the fall in property value. The payment was withheld pending an appeal by Network Rail, which was resolved and saw the two men both receiving their money.

The Appeal Court said that the men were entitled to the full payment, although the judgment said that the £10,000 payments were to compensate them for the inability to enjoy their property rather than the loss of potential value.

Identifying Japanese Knotweed

If you do suspect an infestation of Japanese Knotweed on your or your neighbour’s property, you can send us a photo for a free, no-obligation check. To talk to one of our advisors about Japanese Knotweed or any of our removal methods you can get in touch with Japanese Knotweed Specialists or give us a call on 0800 122 3326.

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How Do You Avoid The Consequences of Japanese Knotweed?

The best option to avoid the consequences of Japanese Knotweed is to remove the Japanese knotweed using one of a few methods known to be effective.

Excavation is one means of eradicating Japanese Knotweed from your land. It is the fastest means to rid yourself of the weed and a legal requirement if the land is intended for development in the future.

However, even the tiniest trace of rhizome left behind in the soil can regrow, for this reason, the best solution is to use a professional Japanese Knotweed company, which will provide you with a certificate guaranteeing the weed has been eradicated.

Spray herbicides are the best solution for large infestations in areas that are not ecologically sensitive. The herbicide is applied to the leaves and absorbed down into the rhizome. This treatment normally takes 24 months.

Stem injection is used when you don’t want to affect other nearby plants whilst eliminating Japanese Knotweed. By injecting the herbicide directly into the stem it is absorbed throughout the rhizome deep into the plant’s root system.

If you have Japanese Knotweed on your property and need it removed, we can help! Speak to one of our specialists today.

About the Author: Adam Brindle

Adam is the Founder and CEO of Grounds Care Group, the parent company of Japanese Knotweed Specialists. He's dedicated more than a decade of his career to revolutionising the grounds maintenance industry and is committed to investing in technology to continuously improve and refine service delivery. Japanese Knotweed Specialists treat and control invasive species like bamboo, giant hogweed, Himalayan balsam and most importantly, Japanese knotweed.

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