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Japanese knotweed: A growing concern

In CategoryTim Whitcombe
ByGardenAdvice Tim Whitcombe

By Stuart Snape, Managing Partner, Graham Coffey & Co. Solicitors 

Japanese knotweed – hollow wooded stems (like bamboo) with broad oval leaves. These plants are relentless and invasive. 

There is nothing new about Japanese knotweed.  If you have sold or bought a house in the last decade you will have seen the declaration as to whether the property is affected by the damaging plant.

It is such an important issue because it can significantly reduce the value of your property by as much as 10%.

So what has changed? Well the plant itself is still as invasive as ever, but it is not just the plant that is growing. The law surrounding your rights and obligations as a landowner have developed significantly over recent years.

Whether these changes are welcome depends largely on which side of the fence you’re on – literally!

Growing on your property

If you find Japanese knotweed growing on your property then the advice is simple – do not ignore it.  

You have a legal obligation to ensure that the plant does not spread to neighbouring property. If it does then your neighbours can pursue you for loss of value.  If we assume average house prices are around £250,000 then that’s a whopping £25,000 claim that could land on your doorstep.

It is important to understand how easily and quickly this plant can spread. Most often it is the root system that grows beneath ground but also disturbing and inadvertently transporting soil contaminated with Japanese Knotweed can lead to new infestations.  A fragment as small as 0.7g stuck to the sole of your shoe can take hold and produce a new plant.

So how do you treat it?

Contact an expert. Do not try and dig it up, burn it, cover it up with a blanket or encourage your dog to eat it.  

Destroying Japanese knotweed can be expensive. Whilst there is no law requiring you to hire a specialist contractor, there are strict rules and conditions associated with its removal and disposal. If you are caught dumping Japanese knotweed or contaminated soil you could face a large fine or even prison. This could include putting it in your green waste bin!

If in doubt you should contact the Environment Agency or the relevant local council for further advice.

In most cases an expert can provide a suitable treatment plan which in many cases will be enough to satisfy any prospective buyer or mortgage company. Always insist on an insurance-backed guarantee!

Be sure to ask the expert whether they are able to identify where the Japanese knotweed came from. It may be possible to see evidence on nearby or adjoining land. If the expert thinks it has spread to your property from neighbouring land then you should seek specialist legal advice straight away.

Likewise, see if the expert is able to identify how long the knotweed has been present. If it likely that it was present when you bought the property and you were not advised either by the seller or your Surveyor then seek specialist legal advice immediately.


Growing alongside your property

If Japanese knotweed is growing on neighbouring land and is within seven meters, there is a real risk that the roots have already encroached beneath your property. From that moment your home and its value can be affected. You should contact a specialist solicitor straight away.

Where Japanese knotweed can be shown to have encroached onto your property, even if that encroachment is only minimal, then you may be entitled to seek compensation for the loss of value to your property, in addition, to an order compelling the owner of the adjoining land to remove the invasive plant.

In many cases, the reduction in value can be as much as 10% and the cost of removing the Japanese knotweed can run into thousands of pounds. It is vital you obtain legal advice to ensure this cost can be passed onto the responsible party. Even if you have no intention of selling the property you may be entitled to claim for the reduction in value.

Legal advice is often essential where Japanese knotweed has been identified and you should not hesitate to contact a specialist legal advisor.

Japanese knotweed has been allowed to grow on railway embankments for years.  In the old days, embankments were often kept clear of vegetation to avoid lineside fires being caused by stray sparks from a passing steam train, but as the railway industry ran out of steam so did their enthusiasm for clearing embankments. Knotweed has spread rapidly and homes built alongside those embankments are at risk of encroachment by the invasive weed.

Always check adjoining land for signs of Japanese knotweed and speak with neighbours. As Japanese knotweed continues to grow and spread the only real defence is awareness.


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