Is the Japanese Knotweed problem under control in the UK?

It’s widely accepted that Japanese knotweed (Fallopia japonica) is an invasive plant species that can lead to structural problems, prosecutions, and in some cases inability to secure a mortgage. But where have we got to with controlling knotweed since it first became a national problem?

Since Japanese knotweed was introduced to the UK in the 19th century it has spread rapidly throughout the country, causing millions of pounds in damage and claims each year. With its ability to grow up to 20cm in a single day and its extensive root system, reported issues such as structural damage to buildings, footpaths, and roads are increasingly in the news. But is the Japanese knotweed problem under control in the UK? Let’s look at some of the measures and legislation that have been put in place over the years, and what’s happening currently to improve the situation.

Awareness and Education


One of the key factors in controlling the Japanese knotweed problem in the UK is awareness and education. The public needs to be informed of the issues with Japanese knotweed and how to identify it. Many people don’t realise that the plant is growing on their property until it’s too late, and by that time, the plant may have already caused some damage. There are stories of surveyors mis-identifying it as another harmless species, and homeowners hiding it under black plastic bags (yes this is happening) are hoping that smothering it will kill it off. Wrong!

By providing accurate information to the general public, and training staff who work on land (such as commercial surveyors, construction firms and developers) we can begin to gain more traction in controlling knotweed. Equally important is getting a survey done as soon as possible, as once identified on a construction site for instance, the project must immediately be placed on hold until the infestation is treated or removed.

Control Measures

Professionally provided control measures do help stop the spread. Whilst an array of suggested ‘solutions’ have come and gone over the years, in general the weed control industry agrees that one of the most effective methods to use is planned herbicide treatments which are typically applied in the late summer or early autumn when the plant is in full growth. Alternatively to completely eradicate the problem we use excavation methods to physically remove the plant and its root system and prevent it from growing back. Just adding to the herbicide treatment – the use of Glyphosate has become a hot topic as to its efficacy and safety. If used correctly there is no better product on the market for a long-term solution, and isn’t that what the UK needs in order to gain control? Ok so various new methods are being brought to market, such as the more gentle vacuum excavation which is used in sites that have pipes, cables or trees to navigate around. Other systems using steam or electricity come with positives and negatives (pardon the pun) – and not all good when looking long-term.

Government Regulations

The UK government has implemented regulations to help control the spread of Japanese knotweed. Under the Wildlife and Countryside Act 1981, it is illegal to plant or grow Japanese knotweed in the wild. The government also requires homeowners to report any sightings of the plant to the appropriate authorities, and failure to do so can result in fines or other penalties. These regulations help to limit the spread of Japanese knotweed and protect the environment.

Property and mortgage implications

The Japanese knotweed problem has significant implications for property owners in the UK. Most mortgage companies will refuse to lend if any Japanese knotweed is disclosed as being on the property. This can make it difficult for property owners to sell their homes, as potential buyers may be hesitant to purchase a property that is contaminated with Japanese knotweed and can therefore cause a depreciation in the property value. But we have to see that these measures have been put in place for a reason – to stop the spread! Failure to be honest and tell the truth when selling a property is a serious issue, as recently highlighted by a legal case ending up with a £200,000 bill.

Ongoing Challenges

Despite the efforts of government agencies, the public, and mortgage lenders to ensure that guidelines are adhered to, the Japanese knotweed problem is far from being under control in the UK. The ongoing challenge is compounded by the fact that the plant produces seeds that can survive for up to 20 years in the soil, and the rhizomes can extend up to 7 meters underground, and only a trained eye can correctly identify the species. It goes back to education and training – much needed for individuals and commercial businesses alike.

In conclusion

Japanese Knotweed remains (for now) a serious problem in the UK, and there are an estimated 1.45 million properties in the UK affected by Japanese Knotweed. However, it is possible to control ‘the spread’ of the plant, but this must be carried out by professional companies licenced to deal with knotweed waste material.

Property owners and developers, commercial businesses, surveyors and government agencies all need to continue their efforts to control the spread of Japanese knotweed, and this means investing in long-term treatment plans, or excavation. It also means making sure staff are trained to identify Japanese knotweed.

Biosecurity measures should be enforced to reduce the risk of transporting fragments of knotweed onto another site or area of land.

And lastly, if Japanese Knotweed is suspected, it’s important to take immediate action such as getting it correctly identified and having a survey booked. For more information, these quicklinks will be useful:

What is Japanese knotweed?

Japanese knotweed and the law

Japanese knotweed damage

This article was written by Jennifer Holmes, Japanese Knotweed Ltd

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