Guidance note on Japanese Knotweed

1. What is Japanese Knotweed?

1.1 Japanese Knotweed (Polygonum cuspidatum/Fallopia japonica) was introduced into the UK in the mid nineteenth century as an ornamental plant but has since spread into wild habitats and has caused severe problems. The plant shades out native species, provides a poor habitat for insects, birds and mammals and can cause structural damage. Japanese Knotweed will penetrate tarmac and concrete, and is very difficult and costly to remove once it has become established.

1.2 The plant regenerates through an underground system of roots (rhizome) or from the base of the stem, and if these are not removed, rapid regrowth occurs. A mere centimetre of rhizome left in the soil is sufficient for the plant to completely regenerate, and any soil within 7m of a single plant can contain enough rhizome for regrowth. Cutting Japanese Knotweed with a mower or strimmer will scatter stems and merely causes the plant to spread. Once the plant is established, effective removal can involve large-scale excavation and treatment with herbicides over a period of several years.

2. Why is this of concern?

2.1 Not only are the costs of dealing with this plant significant, but permitting Japanese Knotweed to grow in the wild, and failing to dispose of it in a reasonable manner can result in prosecution and give rise to potential civil liability.

2.2 The direct costs of removal can be significant. It is not inconceivable that the presence of Japanese Knotweed could delay or otherwise impact upon development at the site and therefore give rise to indirect costs.

2.3 For these reasons Japanese Knotweed should be a due diligence issue (see section 6 below).

3. Statutory Liability

Wildlife and Countryside Act 1981 (WCA)

3.1 Section 14(2) of the WCA states that it is an offence for any person to plant or otherwise cause Japanese Knotweed to grow in the wild. The maximum punishment for such an offence is (1) on summary conviction a fine of £20,000 and/or six months in prison or (2) in the Crown Court an unlimited fine or 2 years in prison. The “regulator for this offence is the relevant local authority.

3.2 A statutory defence is available where the accused took all reasonable steps and exercised all due diligence to avoid committing the offence. To avoid liability under this provision, the Japanese Knotweed should be dealt with promptly in accordance with the Environment Agency Code of Practice for the Management, Destruction and Disposal of Japanese Knotweed (the “Code) a copy of which is available at: http://www.environment-agency.gov.uk/commondata/105385/knotweed.pdf

3.3 It should be noted that due to the persistent nature of this species, it might not be sufficient to merely manage and destroy the current infestation of the Japanese Knotweed to avoid committing the offence. In addition to eradicating the current infestation, the area should be monitored on a regular basis and, in accordance with the Code, any necessary further action taken.

3.4 In addition, there may be a defence if the commission of the offence was due to the act or default of another person. In order to rely on this defence, a notice must be served on the prosecutor at least seven clear days before the date set for a hearing, giving such information held by the defendant in relation to the identity of that third party. Thus for instance, if the Japanese Knotweed is present on site A as result of it spreading from an adjacent site B, the owner or occupier (or other person connected with) site A might claim that the culpable party is the owner or occupier of site B (or other person connected with site B).

Environmental Protection Act 1990 (EPA) / Waste Management Licensing Regulations 1994 (WMLR)

3.5 Under the EPA and WMLR, cut Japanese Knotweed will constitute controlled waste. Liability can therefore also be incurred under sections 33 and 34 of the EPA in relation to any unlawful disposal or handling of waste Japanese Knotweed or waste materials contaminated with Japanese Knotweed.

Enforcement

3.6 Under the WCA the local authority is responsible for inspection and initiating prosecutions for offences. However, there would appear to be a wide variation across the country in relation to the awareness, monitoring and enforcement by local authorities. Not surprisingly, in areas where Japanese Knotweed is a significant problem (eg. Cornwall and South Wales), local authorities tend to have a more active approach.

3.7 The Environment Agency will be the regulator in relation to waste aspects of Japanese Knotweed.

4. Common Law Liability

Private Nuisance

4.1 Failure to manage Japanese Knotweed effectively could conceivably give rise to liability in nuisance if the plant encroaches onto another person’s land.

4.2 Previous occupiers of a site who caused a nuisance can remain liable once they leave occupation and new occupiers of a site allowing a nuisance to continue can “adopt an existing nuisance and hence assume liability.

Negligence

4.3 Failure to take steps to treat and dispose of Japanese Knotweed effectively could conceivably give rise to a claim from neighbouring landowners in negligence should they suffer a loss.

4.4 As with nuisance, previous occupiers, once they have left occupation, could remain liable to third parties and the current occupiers can assume liability for a continuing breach.

Trespass

4.5 It is theoretically possible that if the Japanese Knotweed was allowed to encroach onto a neighbouring site, this encroachment could constitute trespass. Trespass is not often relied upon in cases of this nature.

Contract – leases

4.6 The terms of a lease may give recourse by one party against another. Standard clauses that may provide a cause of action include:

4.6.1 To keep premises in good and substantial condition;
4.6.2 Defects;
4.6.3 Prohibition against nuisance;
4.6.4 Compliance with law

5. Who will be liable?

5.1 Depending upon the circumstances, the range of potentially liable parties under the WCA could include the current landlord, freeholder and tenant, the former landlord, freeholder and tenant or third parties. A third party may be responsible, for example where the Japanese Knotweed has encroached on land from a neighbouring site. To achieve any certainty, the location and time at which the infestation originated needs to be determined. This may require a survey by expert consultants.

6. Due Diligence

6.1 Due to the rule of caveat emptor it is prudent when acquiring a new site, that an enquiry be made in relation to the presence of Japanese Knotweed. It is to be noted that riverbanks, derelict land, roadsides and land close to railway embankments are particularly susceptible to infestation and you should bear this in mind in due diligence.

6.2 The wording of a standard enquiry could be along the lines of:

“Is the Seller aware of there being any Japanese Knotweed currently or previously on the site? If so, please supply details including , where appropriate, details, of the removal of the plant from the site and the procedures used to remove the plant.

6.3 If Japanese Knotweed is discovered, the purchaser may wish to consider whether it needs to reflect the cost of removal in the purchase price and/or otherwise seek contractual terms to reflect the cost of treatment (or any delay caused to planned development at the site).

7. How is Japanese Knotweed Lawfully Disposed of?

On site disposal

7.1 Under the Waste Management Regulations 1994 and the Code, once Japanese Knotweed has been cut, it can be stored on an area of the site that will not be disturbed. When the materials have dried out they can then be burned or buried on site without the need for a waste management licence. Burning is only permitted, however:

7.1.1 on the land where the Japanese Knotweed was present; and
7.1.2 must be conducted in accordance with local byelaws; and
7.1.3 the local Environment Agency office should be informed one week prior to any burning or burying activities.

7.2 Where contaminated waste material is to be buried on-site, provided this activity is conducted in accordance with the Code, then a waste management licence is unlikely to be required and enforcement action is unlikely to result. The provisions of the Code should, therefore, be considered carefully prior to any treatment of the Japanese Knotweed. This will ensure that the correct procedures are followed and that site has sufficient capacity to bury the contaminated material effectively to avoid further infestation without the risk of re-excavation.

7.3 Any on-site treatment and disposal of the Japanese Knotweed should be conducted by a specialist contractor who is authorised to conduct the necessary works.

Disposal to landfill

7.4 Under Section 34 of the EPA, there is a legal duty of care to ensure that waste is properly dealt with. Where the contaminated material is to be deposited off-site at a landfill facility, it is important to ensure that a specialist contractor is used to transport any contaminated waste materials and that the contractor and the landfill operators are informed of the presence of the Japanese Knotweed. The contractor should take care to ensure that contaminated materials are not carried off the site on the wheels of vehicles. This, of course, also applies to all vehicles that are permitted on to the infected part of the premises. They should ensure that:

7.4.1 The landfill operator is licensed to receive this waste;
7.4.2 The landfill has sufficient capacity to receive it bearing in mind that soil containing Japanese Knotweed should be buried to a depth of 5 meters and at least 7 meters from the margins of the landfill or any drains etc; and
7.4.3 The landfill operator has been informed of the presence of viable Japanese Knotweed.

For further information please contact Paul Sheridan on +44 (0)20 7367 2186 or at [email protected]