Invasive non-native species (INNS) are plants and animals that are introduced accidently or deliberately into a natural environment where they are not normally found, with serious negative consequences for their new environment.
This note summarises, very briefly, the practical and legal issues with a focus on a key problem species, Japanese knotweed (knotweed).
This is a particularly hot topic at present, with many lenders citing this as a concern. A significant rise has also been seen in claims for negligence against surveyors where its existence has not been spotted. These factors have led to the recent increase in negative attention given to knotweed in the media which has, in turn, resulted in this being potentially off-putting, perhaps unfairly so, for some buyers.
Japanese knotweed – History
Knotweed was introduced into Great Britain in the 19th century as an ornamental plant. It is now the most invasive plant in the UK. It is a perennial plant that spreads rapidly by its roots (rhizomes) and stems and is extremely difficult to eradicate from land. It can grow up to 10cm a day between the months of April and October. The roots can extend to a depth of three metres and up to seven metres laterally. If even a small piece of root or stem is left in the ground, it can reinfest the land. Its vigorous roots and top growth penetrate foundations, concrete hardstanding and walls, causing considerable damage. The costs of knotweed removal and treatment are substantial.
The House of Commons Science and Technology Select Committee’s 2019 report, Japanese knotweed and the built environment, points out that the latest research suggests that the physical damage to property from Japanese knotweed is no greater than that of other disruptive plants and trees that are not subject to the same control. However, Japanese knotweed is particularly hard to eradicate compared with other plants, requiring multi-year treatment with herbicide or excavation and there is also an ongoing risk that the plant will regrow, either because it is only made dormant by herbicides or because fragments of the plant remain in the soil.
Owner’s and occupier’s liability for INNS
No general duty to control, remove or report
The owner or occupier of land is not obliged to control, remove, eradicate or treat plant INNS, including knotweed. However, failure to take reasonable measures to control knotweed that 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 section 14 of the WCA 1981 (see above). Therefore, it is prudent land management to take action promptly to control the spread of plant INNS.
Property transactions and Japanese knotweed
Contrary to popular belief, there is no blanket policy from lenders which prevents them from lending on properties that have knotweed, although the difficulty in treating it has led to some historical reluctance to lend.
Buildings insurance policies generally do not cover damage and problems caused by knotweed. Where work is done to eradicate knotweed, it is worth considering whether to use a specialist company that provides a guarantee of ongoing treatment cover if the knotweed regrows or the original work was faulty. This guarantee may be backed by insurance, and so can offer protection if the original company has ceased to trade. Many insurance-backed guarantees will be acceptable to most lenders. Ideally, the guarantee provider should at least be a member of the PCA (Property Care Association – https://www.property-care.org/skill/invasive-weed-control/ ).
Pre-contract enquiries – what can be established prior to purchase?
The common law principle of caveat emptor (buyer beware) means that (subject to some exceptions), where property is sold or let, the seller or landlord is not under a duty to disclose any information about the physical condition of the property. That said, the Law Society standard pre contract enquiries forms certainly for residential property, and arguably for commercial property, contain questions that ought to reveal if a Seller has actual knowledge of knotweed on the land. It is likely therefore that this is something that will need to be revealed to future buyers, especially as there is already an ongoing move towards an increase in the obligations of Sellers to reveal known problems or defects. As a Seller you should be very wary about giving an absolute “no” in response to this question if you are not absolutely sure and the form contains a “not known” option which is usually advisable to use.
UK Finance (incorporating the Council of Mortgage Lenders (CML)) has stated that mortgage lenders will expect the presence of knotweed to be noted on a residential valuation report. Lenders determine their individual policies on this issue. If knotweed is present, it is usually one of a number of factors the lender will consider. The level of severity may be a factor. If a mortgage lender agrees to lend on an affected property, it will normally require evidence of treatment that will eradicate the plant as a condition of lending. Red Book guidance from the Royal Institution of Chartered Surveyors (RICS) requires the valuer to indicate the presence of “invasive vegetation”.
In 2012, RICS published an information paper, Japanese Knotweed and residential property. The information paper sets out a standardised methodology for assessing the risks and quantifying the costs associated with knotweed on residential property when carrying out valuations and surveys. This will assist surveyors who are engaged to inspect the property and report on its condition. Not all surveyors are engaged on this basis (for example, some lenders merely instruct a surveyor to provide a valuation, without inspection).
According to RICS, most knotweed infestations are not as severe or as costly as many people (including lenders) think. Having a standardised approach to assessing the risks and costs enables knotweed to be dealt with as just one of many factors that need to be taken into account when valuing a residential property, as opposed to it being a deal breaker.
The Royal Institute of Chartered Surveyors (RICS) have provided their own detailed guide for homeowners and surveyors which expands on the issues touched upon within this note with further, more detailed guidance and can be downloaded from here:
There have been calls however to update the guide as it was published in 2012 and prior to more recent research which may counter the “fear” surrounding this plant. This “fear factor” and other elements and possible updates to the formal RICS advice were discussed by the House of Commons Science Committee in 2019 and you can read that report here:
To date however, no second edition of the RICS report has been published and it remains the guide from which survey reports will be prepared.
Horwood & James LLP