Have you heard the one about the landowner, the developer, the mortgage lender and the gardener?  It’s not a joke!  The one thing they all have in common is a fear of Japanese knotweed.

It may look harmless but Japanese knotweed is no laughing matter.  In 2014, a man murdered his wife before killing himself fearing that his home was being invaded by Japanese Knotweed from the neighbouring golf course.

What is Japanese Knotweed?

It is a plant with large heart-shaped green leaves and a hollow stem like bamboo (though it is not related) with clusters of cream flowers towards the end of July and dies back between September and November leaving brown stems.

Where does it come from?

Japan.  Yes, really!

It was introduced to Britain in Victorian times as a plant for ornamental gardens but roads, rivers and railway lines have assisted in spreading it, with brownfield sites being a common habitat particularly where fly tipping may have introduced stem fragments.

Why is it a problem?

It has a really wide-ranging root system, which can extend up to 3 metres in depth and 7 metres in all directions.  At its most prolific it can grow over 3 metres high in just 10 weeks and while it does not produce seeds, a finger nail size fragment is enough to grow into a whole new plant meaning it spreads easily.  Trying to dispose of Japanese knotweed yourself is virtually impossible.

Its invasive root system and strong growth that can crack tarmac, block drains, undermine foundations and damage buildings, roads, paving and retaining walls.  It can also reduce the capacity of flood defence channels to carry water.

The Environment Agency has described it as being “indisputably the UK’s most aggressive, destructive and invasive plant” and its presence can be enough to reduce a property’s value or even prevent a mortgage lender approving a loan making a property potentially unsaleable.[i]

What is the law on Knotweed?

  • It is not an offence to have Japanese knotweed on your land. However, it is a criminal offence to plant Japanese knotweed or otherwise cause it to grow in the wild. [ii]
  • Allowing it to encroach onto your neighbour’s property may constitute a private nuisance under common law and a land owner may be able to apply for a court order to stop the nuisance or claim compensation for damages.
  • Local councils or police forces can now issue a Community Protection Notice forcing neighbours to take action and fining up to £2,500 if they don’t. [iii]
  • Japanese knotweed is classified as “controlled waste” under the Environmental Protection Act 1990 so don’t take it to your local council dump as it needs specialist waste management and you can face an unlimited fine or even imprisonment for up to two years if it isn‘t disposed of properly.

Why has it been in the news recently?

In two County Court cases this year Network Rail has been held liable in nuisance for damage to amenity of property caused by the presence of knotweed.  Two homeowners in South Wales were awarded £15,000 each to compensate for knotweed which had spread to their gardens as Network Rail ought to have known that the presence of Japanese knotweed created a risk to the claimants and failed to take sufficient steps to eradicate it. [iv]

Can I get rid of it?

  • Use chemicals such as glyphosate and/or imazapyr but it can take up to five years’ treatment to get rid of the plant and professional treatment can be expensive costing over £30,000 for a major infestation.
  • Dig it up but if you leave any trace of its root system then it will grow again. Also, be careful about getting rid of it once it is dug to ensure that it is disposed of lawfully.
  • Take advice from The Invasive Non-Native Specialists Association (INNSA) or the Property Care Association (PCA) for a list of approved treatment firms at property-care.org.
  • For information on Japanese knotweed go to RICS.org.uk.

Is it close to my property?

The Environment Agency has commissioned an app called PlantTracker to track Japanese knotweed.  Those looking for a property can find out if knotweed has been found nearby.  However, just because Japanese knotweed isn’t on the app doesn’t mean that it isn’t present; it simply means it hasn’t been reported.

Can I get any relief from this problem?

Land remediation tax relief is available for the cost of removing Japanese knotweed unless the material was sent to the landfill for disposal as waste land allows companies to deduct an amount equal to 150% of the qualifying clean-up cost when calculating the taxable profits for corporation tax purposes.

What do I do if all else fails?

Eat it!

The young stems are edible as a spring vegetable with a flavour apparently similar to extremely sour rhubarb, although you would need to eat a lot to eradicate the problem.

So, here’s the plan.  Open a chain of sushi bars that cater exclusively to lawyers and serve it as a new dish called Sosumi.

Knotty problem solved!

This post was written by legal director Chris Cheatle. 

[i]  https://www.cml.org.uk/policy/policy-updates/all/japanese-knotweed/

[ii] Section 14(1) and (2) of the Wildlife and Countryside Act 1981

[iii] Anti-Social Behaviour, Crime and Policing Act 2014

[iv] Waistell –v- Network Rail Infrastructure Limited; and Williams –v- Network Rail Infrastructure Limited


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This blog is intended only as a synopsis of certain recent developments. If any matter referred to in this blog is sought to be relied upon, further advice should be obtained.