The Basics of Japanese Knotweed

Our Senior Associate Solicitor, Natalie Forshaw has a wealth of experience in handling cases involving residential and commercial properties disputes, including Japanese knotweed. In this article, Natalie explains further what Japanese Knotweed is, how to identify it and why it’s so bad.

Firstly, what is Japanese Knotweed?

Japanese Knotweed is a non-native plant to the UK that was first introduced in early 19th Century as an ornamental plant.

It is also known by the Latin name of “Fallobia Japonica” and is in fact a “weed” which supresses other plant growth and can be extremely difficult to eradicate. 

How can you identify Japanese Knotweed?

Above ground, Japanese Knotweed changes with the seasons, giving it three very distinctive appearances. The first is that of springtime when its reddish/purple shoots, which look similar to that of asparagus, begin to appear through pinkish buds at ground level.


As the season changes to summer, the shoots grow rapidly and begin to develop into purple speckled like stems which look very similar to that of bamboo and can grow to 2.1 metres in height. The top of the plant has a heart shaped leaves that deepen into green in colour.



Towards the latter part of the summer towards the beginning of autumn, the flower will being to bloom producing cream flowers that can reach up to 15 cm.


The leaves begin to turn yellow and the stem will begin to change from a deep red colour to a very dark shade of brown.




As we approach winter, the Japanese Knotweed plant becomes dormant, the leaves drop and its dark brown bamboo-like canes (which by now are hollow) begin to collapse causing them to become intertwined and somewhat “messy” in appearance.

Below ground, the Rhizome part of the Japanese Knotweed plant is the part that grows underground and can be identified as being very dark brown in colour and able to be snapped like a carrot. The inside of the Rhizome is a mix of between yellow and orange in colour.

Many individuals confuse Japanese Knotweed with other plants, such as the Russian Vine and the Himalayan Honeysuckle plants.  Therefore, it’s advisable to seek the assistance of a professional to help in identification of the weed.

Scary fact 1

It is this Japanese Knotweed Rhizome system that is the most dangerous and it can grow to depths of 2 metres and can extend up to 7 metres horizontally from the plant.  In the UK, we only have female plants which mean that they cannot be spread by way of seed and it is thus the Rhizome system that gives rise to a new plant.  In fact, as little as 0.7 grams of a viable Rhizome can give rise to an entirely new plant.

Why is Japanese Knotweed so bad?

Japanese Knotweed has an extremely negative impact on almost everything that it encounters.  It can cause significant issues in respect of the development of land as well as structural damage to properties as it creeps into bricks, cavity walls and other structural components of a building. In fact, there have even been reports of it emerging through concrete! Plus, it’s incredibly difficult to remove.

Scary fact 2

In a 2010 survey by Williams Et Al it was estimated that almost 10% of rivers in the country were infested with Japanese Knotweed. 

Treatment and Removal

You can try your best to remove Japanese Knotweed but unless you have sought the assistance of a specialist, you will likely be unsuccessful.  Many people have tried killing the plant by dousing it and the area in which it sits in bleach. This is in no way shape or form a way of destroying it and instead will simply result in unnecessary damage to the environment.  Instead, I would urge you to contact either a professional treatment company, who will treat the plant with a chemical called Glyphosate, or a professional removal company who will to dig out the entire growth of the plant.

It generally takes between three to four seasons to completely eradicate the plant by using Glyphosate products and if you decide to dig out the Knotweed, then it’s likely that regrowth will occur. 

Scary fact 3

Employment of a specialist company is often required for your insurance to be valid as there are very tight regulations around the disposal of Japanese Knotweed that need to be complied with. This is because it is classed as “controlled waste” under the Environmental Protection Act 1990 and must be disposed of at licensed landfill sites. 

Criminal Liability

Scary fact 4

It’s probably fair to highlight that all of the information found below represents a “scary fact” because you certainly don’t want to fall foul of the legislation because the consequences are severe! There are up to ten pieces of legislation regarding prevention, treatment, removal and disposal so the following is simply a “snippet” of information:-

It is an offence under Section 14(2) of the Wildlife and Countryside Act 1981 for any person to “cause to grow in the wild” a plant in Part 2 of Schedule 9, this includes Japanese Knotweed and other invasive non-native species such as hybrids of knotweed and giant hogweed.

Further, a Local Authority can serve a notice on an occupier under Section 215 of the Town and Country Planning Act 1990 to remove Japanese Knotweed if the amenity of an area or of an adjoining area, is “adversely affected”.  The occupier can then be fined in a Magistrates Court and the Authority can step in to undertake the works and recover its reasonable costs if necessary. 

Further, the Antisocial Behaviour, Crime and Policing Act 2014 means that individuals, as well as organisations could be served with Community Protection Notices for failing to control Japanese Knotweed when they could be reasonably expected to do so.  A conviction under this Act is a criminal offence and those individuals, as well as companies, could face fines.

In fact, in December 2018 a property owner, who had failed to respond to a Community Protection Notice issued in 2017 appeared in front of the Bristol Magistrates Court and was ordered to pay £18,000.00 for failing to prevent the spread of Japanese Knotweed originated on the landowner’s property.  This was thought to be the first prosecution under this Act to tackle the issue of the spread of Japanese Knotweed.

If you fail to dispose of the Japanese Knotweed correctly, then you can also be convicted and imprisoned for a term not exceeding 6 months in the Magistrates Court instead of a fine or both. If convicted in the Crown Court it could run to a 2 year jail term or an unlimited fine.

Further, the Waste (England and Wales) Regulations 2011 which provide the Environmental Agency with a range of enforcement tools relating to compliance, stock and restoration notices.  They also create more offences of non-compliance with these notices.

Then… to top it all off, there’s also a civil responsibility to prohibit the encroachment of Japanese Knotweed onto neighbouring land, failing which you could be faced with a claim in nuisance for loss of enjoyment… even before the Knotweed has caused physical damage.

If you have been affected this by this article or have found yourself with nowhere to turn, then please speak with our specialist Senior Litigator, Natalie Forshaw on 01249 444499 who would be happy to advise you on the appropriate steps to be taken.

If you have found this article helpful, then please read my next two upcoming articles, the first aptly titled “Buyer Beware”; concerning the steps that a buyer can take to avoid purchasing land and/ property suffering an invasion of Japanese Knotweed and the second titled “Claiming for Japanese Knotweed” and concerning what’s involved in making a civil claim for nuisance.