Understanding the risks around invasive plant encroachment

Environet has written an article that assesses and discusses how to understand the risks around invasive plant encroachment.

It isn’t illegal to have invasive plants growing on a property, but when they spread across boundaries into adjoining properties they can cause damage, negatively impact values and prompt legal disputes between neighbours.

So, what are the risks to buyers of property under threat or already impacted by encroachment – and what are the implications for property professionals when such properties are bought and sold?

The law around encroachment

Where Japanese knotweed or bamboo is growing, it’s the landowner’s responsibility to ensure that the plant does not spread into adjacent properties, causing nuisance, impacting that homeowner’s enjoyment of their home/garden and potentially its value. 

There are now numerous legal cases relating to knotweed encroachment, where the victim has successfully sued the offending homeowner, and cases of legal disputes arising from bamboo encroachment are also on the rise. The mere presence of knotweed is enough to support a nuisance claim because it restricts the owner’s use and enjoyment by limiting their ability to develop the property, and by unfairly placing an immediate burden on them to take steps to eradicate it. 

Repair to damage caused, for example to homes, outbuildings, paths, driveways and patios, can also be claimed for.

The TA6 form is the first line of defence

Buyers of property under immediate threat or impacted by encroachment of Japanese knotweed are protected in the first instance by the TA6 form. For a seller to tick “No” to the Japanese knotweed question, they must be certain that no rhizome (root) is present in the ground of the property, or within 3 metres of the boundary, even if there are no visible signs above ground. This clearly takes into account encroachment risk and paves the way for a legal claim against the seller if they answer dishonestly.

The same cannot be said for bamboo, however. While knotweed is rightly the more notorious of the two plants, being by far the more difficult to remove, bamboo can potentially cause greater damage due to its long lateral roots that can extend 30ft or more from the parent plant. 

As yet, nuisance arising from bamboo encroachment has been much less rigorously tested in court than Japanese knotweed, despite the fact that evidence of damage to properties and gardens arising from bamboo is just as strong. This is most likely due to much lower awareness of the risks arising from bamboo. A recent survey we carried out with YouGov showed that while 82% of people would take some kind of action if knotweed began to encroach into their garden, only 24% would be concerned to find bamboo growing on the border of their property.

Any disputes between neighbours over bamboo, knotweed or any other invasive plant should also be declared on the TA6 form, or if the seller is aware of anything that might lead to a dispute. That may provide a further safety net for buyers where invasives are growing on or near a border and the issue has been raised by the previous owner.

Next up, surveyors

The second line of defence is the surveyor, who is obliged to highlight any identifiable risk or potential defect that could impact their client’s decision to purchase the property.  Japanese knotweed growing on and near the property certainly falls into this category, as would any significant stand of invasive bamboo.

It’s my view, however, that RICS have failed to give enough weight to encroachment risk to property buyers in their revised Japanese knotweed Guidance Note, issued to surveyors last year. The 7-metre rule was scrapped but under the new guidance, even if knotweed is within 3 metres of the property’s border (clearly an encroachment threat) surveyors are only required to flag it in the lowest-risk category ‘D’. This could provide a false sense of security to a potential buyer.

In this situation, firstly I would recommend that the surveyor is asked to provide further context. Secondly, it would be wise for the buyer to undertake a specialist survey to assess the risks, check whether the plant’s roots have already crossed the boundary beneath the ground, and make recommendations for protecting the property in the future – for example by installing a root barrier.

Thirdly, it would also be prudent for buyers wishing to proceed with the purchase of a property that is under threat of encroachment to write to the neighbour alerting them to the problem and giving them the opportunity to take action, thereby laying the groundwork for a future legal case should they fail to prevent it.

Armed with the facts

Buyers shouldn’t necessarily walk away from a property under threat from encroachment of Japanese knotweed or bamboo, but they should be fully aware of the potential problems that may arise.

That includes the level of risk as determined by a specialist surveyor, the likely cost of protection and removal, a review of the price they’re willing to pay for the property and its potential diminution if the situation worsens – and finally the stress if they are required to bring a legal case against their new neighbour in the future.

Guidance from surveyors and conveyancers is essential to help buyers assess encroachment risk and obtain information from the seller that may support a legal claim if encroachment later occurs.

Written by Nic Seal, founder of invasive plant specialists Environet.

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