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How serious is Japanese Knotweed for landlords?

The fast-growing, invasive, plant Japanese Knotweed

Japanese Knotweed – two words that can strike fear into the hearts of landlords – and property owners generally.  But what is Japanese Knotweed and how serious a problem is it if you find it in the garden of your property?

Japanese Knotweed (Fallopia Japonica) was brought to the UK in 1850 by a Bavarian doctor as an ornamental plant that was also able to stabilise land including sand dunes and railway embankments. But it’s an extremely invasive weed – it spreads very quickly, with roots that can grow down to a depth of two metres, making it difficult to eradicate, while its dense foliage also makes it difficult for nearby plants to survive.

What problems can be caused by Japanese Knotweed?

Over the last few years Japanese Knotweed has created a real panic amongst homeowners but what damage can it cause?

Typical problems include damage to garden walls that have only shallow foundations, as well as patios and paths where shoots can grow through gaps.  Drains and underground services can also be affected by the roots, as can the foundations of conservatories and outbuildings.  And of course, Knotweed can take over a garden very quickly – and that doesn’t look good for anyone selling or renting a home.

But the good news is that a 2018 study by Leeds University found that structural damage to buildings (from a survey of 122 properties affected by Knotweed) is rare and only happened when there were already structural problems.  In fact, some trees and climbers were found to cause more damage to buildings than Knotweed.

What does Japanese Knotweed look like?

Japanese knotweed. – green leaves and white flowers

Look for a long, hollow stem (similar to bamboo) which starts to grow from the end of April (it can grow up to 10cm a day), clusters of small creamy white flowers (which grow from August to September) and shovel-shaped leaves.  It dies back in the winter but grows again in the spring.

For more help identifying Japanese Knotweed,take a look at The Royal Horticultural Society’s website

What are your responsibilities as a landlord?

Property owners must not let Knotweed spread from their property.  Failure to do this could mean a fine or even imprisonment.

It is listed in the Wildlife and Countryside Act 1981 (Section 14, Schedule 9, Part 11) as a non-native, invasive weed.  It states that ‘ if any person plants or otherwise causes to grow in the wild any plant which is included in Part 11 of Schedule 9, he shall be guilty of an offence’.  Offenders may face a £5,000 fine and/or six months imprisonment, or two years and/or an unlimited fine or indictment.

What should you do if you are a landlord?

If you or your tenant discovers Japanese Knotweed in the garden of your property, you’ll need to look at your Tenancy Agreement to ascertain who is responsible for its removal.  And you’ll need to prove whether or not the Knotweed was already there when the tenant moved in.

Even if the Knotweed is the tenant’s responsibility, it may be wise for the landlord to at least help with the costs of its removal to prevent it damaging the foundations of the property or other structures in the garden.

Options for the removal of Japanese Knotweed

There are two options for removing Knotweed.

First, you can use weed killer.  This is the cheapest option but it can take some time and you won’t know if it has worked until the following spring when it may grow back.  It can take up to five years to completely get rid of the weed.

Secondly, you can dig it up or arrange for a contractor to do this.  It gets rid of the Knotweed more quickly but can work out more expensive.    It also has to be taken to a specialist landfill site (not a general tip) as it’s classified as controlled waste and this can prove expensive too.

We’ve simplified these methods here but the processes for both can be complex.  The Environmental Protection Act 1990 lists appropriate methods of removing, transporting and disposing of controlled waste (including Japanese Knotweed).

Finding a specialist contractor

With such strict regulations as to the disposal of Knotweed, it is usually better to use a specialist contractor to carry out this for you so that you do not inadvertently break the law.

What should you do if you are selling a property?

If you’re selling a property, you are legally required to check whether there is any Japanese Knotweed on your property.  If you find any you must state this on the property information form.  You could be sued if you try to hide this fact.  As the seller, you must provide a management plan for getting rid of the Knotweed using an approved contractor.

The good news is that mortgage lenders are becoming more understanding than they were several years ago, thanks to more efficient methods of dealing with the problem.  So if a surveyor finds Knotweed on a property, it shouldn’t be a dealbreaker.

Contact our property management team for more information

We’re pleased to say that we have not had an incident of Japanese Knotweed on any of our rental properties in London. and as part of our Property Management service, we would be able to instruct an appropriate specialist contractor to treat the problem and dispose the waste according to Gov guidelines.

For more information about our Property Management service, get in touch.


About the Author

Established in 1958, Benham and Reeves is one of London’s oldest, independently owned property lettings and sales agents.  With specialism in residential sales, corporate lettings and property management in prime areas of London, the company operates from 21 prominently located branches and 14 international offices.