Following our article from 19 June 2023 discussing the steps to take if you wish to sell a property that suffers from Japanese knotweed, B P Collins property team has prepared advice for buyers thinking about purchasing a property with this problem.
The owner or occupier of a property is not obliged to control, remove, eradicate, or treat plant invasive non-native species including knotweed, provided there is no reasonably foreseeable risk of spread or damage to other’s property. This means a buyer will need to carefully consider the likelihood of damage occurring or the knotweed spreading. Factors which will need to be considered are the proximity of neighbours, any development plans and closeness to water, as knotweed can spread more aggressively when transported by water.
Consequences of failing to treat Japanese knotweed.
Failure to take reasonable measures to control knotweed which then results in the plant spreading to the wild, or being negligent or reckless about that occurring, could amount to the offence of causing it to grow in the wild under the Wildlife and Countryside Act 1981. There has been no definition of “cause to grow” in the statute, however Defra has interpreted the wording to mean ‘a landowner who knowingly allows a Schedule 9 species (which encompasses knotweed) that it did not introduce, to accumulate on its land and create a problem as it spreads to other areas of the wild, and who makes a conscious decision to do nothing about it.. This interpretation has not yet been assessed in court, however it is a consequence a prospective buyer should be aware of.
Under the Town and Country Planning Act 1990, a property owner could be served a notice requiring them to remedy the condition of the land within a specific period where, in the local authority’s opinion, the amenity of an area (or adjoining area) is adversely affected. This power could be exercised for infestation of land by knotweed, particularly where it is at risk of spreading into adjoining land.
The case of Smith and another v Line (CTR00216) WL 09565854,  established that a party can been found guilty of a common law nuisance offence by allowing Japanese knotweed to spread from their land into their neighbours. The case found that the property owner was guilty of a common law nuisance offence by, “Causing an encroachment on a neighbour’s land which closely resembles trespass. Unduly interfering with a neighbour’s comfortable and convenient enjoyment of their land.”
What can we learn?
The legislation and case law demonstrates that if you are looking to buy a property which is affected by knotweed, simply doing nothing to increase the risk of spread is not sufficient, you will need to consider the likelihood of the risk of the knotweed spreading, and from there you will need to consider taking out remedial measures to eradicate or minimise the impact of the knotweed, and the associated costs.