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What is Japanese knotweed?

What is Japanese knotweed?



Japanese knotweed (Fallopia japonica) is a weed that can grow up to 10cm a day and spreads rapidly. It’s been described as the most destructive and the most widespread plant in the UK.


This has become a major problem across the UK. It could even affect the property by cutting down the prices in as much as 10% and making it hard to be bought or sold. Mortgage lenders may also decline applications to people buying a property in or around the hotspots where the weed is renowned.


The new heat map data shows and identified the hardest-hit areas of knotweed are in the North West England and Wales. The worst affected area with 652 infestations within a 4km radius is in - Bolton, Lancashire. London also suffers from high concentrations of knotweed in many parts.


Listed below are the top Japanese Knotweed hotspots in each region of the UK:


· Bolton, Lancashire

· Bristol

· Capel Garmon, Conwy

· Rotherham

· Nottingham

· Clapham Common

· Glasgow

· Madeley, Shropshire

· Shanklin, Isle of Wight

· Norwich

· Newcastle



Where does knotweed grow?


Knotweed can grow in most soil conditions found in the UK. It’s also commonly found along rivers and streams. This knotweed’s root system causes physical damage for its habit of growing between stonework, patios, drains, damaging the driveways and other man-made structures.



Japanese knotweed and the Law


It’s not illegal to have Japanese knotweed in your garden. However, it could cause disputes with neighbors if you let it get out of hand as they could take a private nuisance action against you. You could be liable for the damage caused or even for the removal costs. Under the Anti-social Behaviour Crime and Policing Act 2014, local authorities can now issue landowners with a Community Protection Notice to formally require them to control the spread of Japanese Knotweed on their land.


On the other hand, under the provisions made within Schedule 9 of the Wildlife and Countryside Act 1981, it is an offence to cause Japanese knotweed to grow and the law seeks to prevent spreading further.



Legal Situation


Here’s a summary from RHS when buying or selling a property where knotweed is present:


· In buying a property:


The presence of Japanese knotweed will be stated in the responses to the TA6 form - is used so that the seller can give important information about the property to the prospective buyer.


This often results in your mortgage lender requiring assurances that it will be eradicated before agreeing the funds. A management plan by a professional eradication company, backed by a transferable guarantee, is usually sufficient. It is most common for this plan to be provided by the seller before the purchase is completed


· If you are selling a property:


You are required to state whether Japanese knotweed is present on the property through a TA6 form.


It is your responsibility to check the area for Japanese knotweed. The TA6 form asks you to confirm whether your property is affected by Japanese knotweed and, where it is, to provide a management plan for its eradication from a professional company.


· Whether a buyer or seller, it is also worth being pro-active and checking the property for Japanese knotweed. Disputes over the identity of a plant, the failure to disclose its presence, or the lack of a management plan can result in delays, increased costs later in the buying process, or even a possible misrepresentation claim after the sale, so this approach will help avoid problems



How to stop it from spreading


The plant is resistant to cutting, as it regrows vigorously – and any cut pieces must be disposed of very carefully. It can be destroyed by chemical herbicides. These actions can help to stop the spread of Japanese knotweed:


· Spray with chemicals


Spraying or injecting the stems with approved chemicals can be an effective treatment to stop knotweeds spreading. It usually takes at least 3 years to treat Japanese knotweed. Knotweed rhizome can remain dormant in the soil for many years and will regrow if disturbed or if the soil is relocated.


· Bury it

Before burying the knotweed, you must notify the Environment Agency at least a month.

You can dispose of the dead brown canes of Japanese knotweed by composting on site, as long as they’re cut (not pulled) a minimum of 10cm above the crown.

You must bury knotweed material:

· on the site it came from, including ash and soils containing potential knotweed propagules

· at a depth of at least 5 meters, if you have not sealed with a material called a geotextile membrane

· at a depth of at least 2 meters, if you have sealed with a geotextile membrane


· Burn it


If you want to burn the knotweed, you must -

· tell the Environment Agency at least a week before you burn it

· tell the environmental health officer at your local council

· get a burning waste in the open exemption (a D7 exemption)

· follow local byelaws and not cause a nuisance


Knotweed crowns and rhizomes may survive burning, so you must follow the guidance for how to bury it or how to dispose of it off site.


· Companies that specialize in treating knotweed

You can manage the disposal of knotweed yourself, or you can hire a specialist to do it for you.

Look for a contractor with the following accreditations and registrations:

· Amenity Forum Membership

· BASIS Professional Register

· BASIS Amenity Training Register

· BASIS Nominated Storekeeper (NSK) Professional Register

Many of these companies belong to one of these trade bodies:

· Invasive Non-Native Specialists Association (INNSA)

· Property Care Association (PCA)


Data source: GOV.UK



Removal cost


Costs for Japanese knotweed removal vary depending on the area that has been affected and the form of treatment that you opt for.

To manually remove the rhizomes from beneath 4 square yards of the ground, the costs could be up to £1,000 per visible square yard. You would also have to:

· dig up 20 square yards

· take into account the removal of any paving or pipes

Another option is to attack the plant with a weed killer. It’s a long-term solution but is undeniably cheaper- the costs of around £2,000 to £5,000 are spread out over a number of years.

These may seem to be a big investments but it’s better than simply ignoring your problem. Japanese knotweed can spread like a virus across land and into buildings, leeching anywhere from 5-20% off the value of your home.

Data source: Knotweed help

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