Japanese knotweed can be found almost all over the country. Most of its biomass is below ground. It only needs a small area of bare earth to push shoots through.   It grows strongly and quickly, with its roots penetrating as far as 3 metres deep and 7 metres across.  Left unchecked, it can cause massive damage to house foundations, drainage systems and walls.  Mortgage lenders have been known to refuse mortgages on buildings that are affected by Japanese knotweed. If it’s spotted on a property survey, then a lender is likely to insist on hiring a professional to handle the problem before granting a loan.  Homeowners affected by Japanese knotweed are also likely see a considerable drop in value of the house. Most buildings insurance policies don’t cover damage caused by Japanese knotweed.  If your neighbour has knotweed and your property is affected by it, most insurers are likely to pursue others for the cost of the damage caused to your building.

There are ways to get rid of the dreaded plant but it’s costly:

·       Digging out knotweed is possible, but due to its rapid growth and strength, it’s likely to come back.  There’s also a problem with disposal, as Japanese knotweed is classified as ‘controlled waste’ under the Environmental Protection Act 1990.  So even if you get shot of it, you can only dispose of at licensed landfill sites.  Off-site disposal cost: £10,000.

·       Chemical treatment is usually the cheapest and most effective option. A glyphosate-based weed killer is a popular choice for most gardeners. This method could take more than three years to be effective, though. Professional contractors will have access to stronger weed killers, which may be quicker. Cost: £3,000 - £5,000

·       A plant-sucking bug is being trialled in the UK as a biological control for knotweed.  With a bit of luck, it’ll become available to gardeners if it works.

There is no explicit obligation to manage plants, however, a landowner that 'knowingly allows it to spread into other areas of the wild and makes a conscious decision to do nothing about it' may be committing an offence of 'causing to grow in the wild'.  Reasonable measures  should be taken to confine to the cultivated area so as to prevent their spreading'.

A local authority can serve a notice on an occupier under section 215 of the Town and Country Planning Act 1990 to remove Japanese knotweed if the amenity of an area (or adjoining area) is adversely affected.   The occupier can be fined £1000 in the magistrates' court and the authority can step in to undertake works and recover its reasonable costs.

New rules introduced in the Anti-social Behaviour, Crime and Policing Act 2014 means that people and organisations who fail to control Japanese knotweed could be issued with anti-social behaviour orders if their conduct is having a detrimental effect of a persistent or continuing nature on the quality of life of those in the locality.  Conviction under ABCPA 2014 is a criminal offence and individuals could be fined up to £2,500, with companies facing fines of up to £20,000.

When Japanese knotweed is disposed of, it becomes a controlled waste.

It is an offence to deposit or knowing cause or knowing permit controlled waste to be deposited on land without a permit or in a manner likely to cause pollution of the environment

If convicted in the magistrates' court, magistrates’ can impose unlimited fines upon conviction.

The magistrates' court can also impose a prison term not exceeding six months instead of a fine, or both. In the Crown Court, it could run to a two-year jail term or an unlimited fine.

Do your research before you buy…