This blog examines some of the latest developments in relation to the ongoing concerns over Japanese Knotweed and its hybrid forms.

“Bohemian Knotweed”

The discovery of a new hybrid form of Japanese Knotweed (a cross between Japanese Knotweed and Giant Knotweed) which could be even more destructive than its parent plant, has started another round of concern over the effects of this invasive species. The Property Care Association (PCA) has announced that reports of this hybrid, known as “Bohemian Knotweed” are rising and the ideal recent growing conditions for the weed have increased concern that it might spread rapidly across the UK. Bohemian Knotweed, like its infamous parent, Japanese Knotweed, is a non-native invasive species known to cause damage to concrete, buildings and foundations if left untreated and capable of spreading over 7 metres laterally from the plant. Even when removed, if a small piece of root or stem is left in the ground it can re-infest the land. The costs of knotweed treatment and removal are significant, with the government estimating that the costs of eradicating it from the UK would be £2.6 billion.

The Legal Position

The law on Japanese Knotweed (“Knotweed”), which will equally apply to Bohemian Knotweed, is now well established. Schedule 9 to the Wildlife and Countryside Act 1981 (‘WCA’) lists certain plants and animal invasive non-native species that have become established in the UK but which the law seeks to prevent spreading further. Under s. 14 (2) WCA it is an offence to plant Knotweed or “cause it to grow” in the wild (and arguably this provision would catch allowing knotweed to spread over boundaries beyond an individual’s property).  S14(2) states that “if any person plants or otherwise causes to grow in the wild any plant which is included in Part II of Schedule 9, he shall be guilty of an offence.”  A defence under s.14(3) is that the accused took all reasonable steps and exercised due diligence to avoid committing an offence.  Taking appropriate steps to treat the Knotweed is likely to constitute a defence.

Case Law

Case law recognises the civil wrongs of nuisance, both private and public and these are particularly relevant in Knotweed cases.  A  leading cited Knotweed case is the 2018 case of Network Rail Infrastructure Ltd v Williams and another. The claimants in this case Mr Williams and Mr Waistell, were adjoining freehold owners of semi-detatched bungalows in South Wales. Both of their bungalows abutted a Network Rail railway embankment and access path which were infested with Japanese Knotweed and which had spread to the claimants land. The claimants claimed an injunction requiring the removal or treatment of the Knotweed by Network Rail, as well as damages. Their claims were based on private nuisance – that there was unreasonable interference with their land. The Court held that “damage” (an essential requirement for a common law nuisance case) was an elastic concept and included Knotweed rhizome contamination, and in addition, that nuisance could be caused by inaction or omission as well as by positive activity. The Court awarded each Claimant £10,000 for diminution in value and £4,320 for treating the Knotweed on their land. Each Claimant was also awarded £350 per year as general damages for loss of amenity.

Significant newspaper publicity has also been given to a 2019 court award of £50,000 relating to a case where a visually impaired property owner, Paul Ryb, instructed a chartered surveyor to undertake a comprehensive RICS level 3 survey of a flat in London he wished to purchase. The surveyor reported that the property was in excellent condition with very few defects, but missed the actively growing mature Knotweed in the garden, which was subsequently identified by Mr Ryb’s gardener. Mr Ryb claimed that his surveyors were negligent in failing to spot signs of the Knotweed despite carrying out a top-grade survey, and claimed damages from the firm. Ruling in Mr Ryb’s favour, Judge Luba said the commissioned report “did fall short of the standard to be required of a reasonably competent surveyor”. The £50,000 figure awarded reflected the reduced value of the property. This case highlights the duty of care on surveyors and other consultants carrying out surveys in relation to the presence of Knotweed on a site.

Interestingly, home owners wishing to sell their property must fill out a property information form, called a TA6, declaring whether the property or garden is, or has been, affected by Knotweed, but developers and builders are not obliged to complete the form, which was introduced in 2013. Knotweed specialists have warned the issue needs to be addressed urgently, calling for builders and developers to also declare the information.

What Next?

The case law and the publicity surrounding Knotweed continues, however the latest research suggests that the physical damage to property from Knotweed is no greater than that of other disruptive plants and trees (such as buddleia) that are not subject to the same controls. This conclusion is supported by the experience of some experts in this area and data from Knotweed contractors. However, Knotweed is particularly hard to eradicate compared with other plants, requiring multi-year treatment with herbicide or excavation, which is not the case with trees or plants such as buddleia.

The UK Government’s latest report on Knotweed published on 16 May 2019 states that “a significant industry is built around controlling Japanese Knotweed, but we were told that mortgage lenders in other countries do not treat the plant with the same degree of caution. This gives us reason to believe that the UK has taken an overly cautious approach to this plant, and that a more measured and evidence-based approach is needed to ensure that the impact is proportionate to the physical effects of the plant in the built environment”. The report goes on to recommend that a study of international approaches to Knotweed in the context of property sales is commissioned. In addition, the study has recommended that the Law Society review its Property Information Forms, in particular to decide whether the need to declare previous Knotweed problems should expire if the plant has been treated by appropriate excavation and there has been no re-growth within a certain period. Both these actions have been recommended for the end of this year. It will be interesting to see if these studies lead to any shift in approach away from the “menace to homeowners” that Knotweed is currently considered to be.