How To: Deal with Japanese Knotweed

How To: Deal Japanese Knotweed

Why is it a problem?

Japanese knotweed (Fallopia japonica) is a non-native plant species to the UK. Without the natural brake on its spread found in its native environment it has taken on an invasive nature.

As well as upsetting the UK’s ecosystem, mature plants can undermine man-made structures. Damage has been recorded in buildings, hard standing, walls and drains.

Japanese knotweed is therefore governed by legislation and a recognised risk to property. In recent years this has seen mortgage lenders refusing to lend on property at risk from knotweed, and required developers to bring in specialists to eradicate the plants on infected sites.

The presence of knotweed on or near your property could therefore present you with a problem.

Who to turn to?

To help homeowners, purchasers and lenders in making informed decisions RICS released the Japanese knotweed and residential property information paper, 1st edition (IP 27/2012). This sets out a framework for objectively assessing and reporting the risk.

RICS also worked with the Property Care Association (PCA) to establish the PCA Invasive Weed Control Group (IWCG) trade body for Japanese knotweed specialists in 2012, which provides a register of reputable vetted consultants and contractors.

What are my options?

Where a known or suspected presence of knotweed is highlighted on a TA6 Property Information Form or by a buildings survey, a Specialist Knotweed Survey should be carried out to establish the risk and advice on a remediation solution.

The majority of UK mortgage lenders will want to see evidence of a commitment by the owner of the property to fund, in advance, a long-term chemical treatment programme effective against Japanese knotweed, or provide instant eradication by way of excavation and removal. This is often referred to as a knotweed management plan.

Chemical treatment can take around 2-3 years to provide effective control of the knotweed. However, it is important to note that this does not remove the rhizome (root) from the ground, which can remain dormant for many years. Where the restriction of ground under treatment is undesirable, or where there are known plans to disturb the ground, the excavation and removal of the knotweed is often preferred.

It is a case of caveat emptor (let the buyer beware). If you can negotiate an instant removal of the knotweed by excavation then do so!

How am I protected?

A guarantee is often required on any remedial works, with durations of 5-10 years being the norm. A guarantee should ensure that should there be any recurrence of knotweed growth (as a defect of the remedial works undertaken) it will be treated and controlled at no additional expense to the property owner.

Because treatment programmes can stretch over many years, mortgage lenders will often look for an insurance backed guarantee (IBG) product, such as that provided by PCA IWCG members. This ensures that in the event that the knotweed contractor providing the guarantee goes out of business before the end of the cover period the customer will be protected by either another PCA registered company stepping in to take on the liability, or a refund of the monetary sum left on the contract. This depends on the terms of your agreement and varies per provider.

Are there any legal requirements?

Under the terms of the revised Anti-social Behaviour, Crime and Policing Act 2014 community protection notices can be used to force landowners to control non-native invasive plants on their property.

After being put on notice, companies can be fined up to £20,000 and individuals up to £2,500, if a lack of action has a detrimental effect on the quality of life of those nearby and is considered to be unreasonable.

Japanese knotweed is not cited under any legislation that requires its presence to be notified to either the Department for Environment, Food and Rural Affairs or local planning authorities; nor is it listed under The Weeds Act 1959.

The spread of Japanese knotweed is, however, governed under the Wildlife and Countryside Act 1981, which makes it an offence  to cause it to grow in the wild, and can be construed as an offence to knowingly allow knotweed to spread from your property.

Under the Environmental Protection Act 1990, Duty of Care Regulations 1991, Japanese knotweed material and material contaminated with Japanese knotweed must be removed to a licensed landfill site for disposal, accompanied by appropriate waste transfer documentation.

Removal of knotweed for development

On development sites, Japanese knotweed needs to be managed and handled responsibly. Any works conducted to control or eradicate the plant should be completed in reference to the Environment Agency and PCA codes of practice for the management of Japanese knotweed.