Does this sound familar? Fallopia japonica, commonly known as Japanese knotweed, is in flower now, and it’s commonly seen in almost every town and city in the country. Biologically it’s a large, herbaceous perennial plant of the family Polygonaceae, native to Eastern Asia in Japan, China and Korea; practically and legally it’s a menace.

It is listed by the World Conservation Union as one of the world’s worst invasive species. Philipp von Siebold transported it from a Japanese volcano to Holland, and in 1850 a specimen was added to the Royal Botanic Gardens, Kew. It was well-liked by gardeners because it looked like bamboo and grew everywhere. It soon became clear that this was a big mistake. The “perfect DNA clones of von Siebold’s disastrous legacy” have spread nationwide. Some land owners are unable to sell their property if there is any evidence of knotweed infestation.

The invasive root system and strong growth can damage concrete foundations, buildings, flood defences, roads, paving,  and retaining walls. It frequently colonises roadsides, forming thick, dense colonies that completely crowd out any other species. It can tolerate a very wide range of soil types, pH and salinity; it can survive temperatures of −35 °C and can extend 7 metres horizontally and 3 metres vertically, making removal by excavation extremely difficult. The plant is also resilient to cutting, vigorously resprouting from the roots. It will regenerate completely from an extremely small fragment but fortunately all the plants in the UK are female. They produce no seeds and can only spread by the rooting of existing plant elements.

In the UK, Japanese knotweed is established in the wild in many parts of the country. It is not an offence to have it growing on your property, but it is an offence under section 14(2) of the Wildlife and Countryside Act 1981 to “plant or otherwise cause to grow in the wild” any plant listed in Schedule nine, Part II to the Act, which includes Japanese knotweed.

The most effective method of control is by herbicide application close to the flowering stage in late summer or autumn, but the species is expensive to remove. It cost millions of pounds to eradicate knotweed on a patch of land on the site of the London 2012 Olympic Games velodrome and aquatic centre. A national eradication programme using traditional methods is prohibitively expensive, but in 2010 a trial was launched using a species of aphid that feeds only of Japanese knotweed, in the hope that it will prove an effective biological agent.

If Japanese knotweed is growing on your property, you can (and certainly should) do something about it urgently. It can prevent a sale of the property (mortgage lenders will usually refuse to lend in these circumstances unless measures have been taken to ameliorate it). You can “do it yourself” by using a herbicide or by excavating and carting away the affected soil, but be aware that disposal of the plant waste requires a special licence; it cannot be done at the local tip. It is classed as “controlled waste” under part 2 of the Environmental Protection Act 1990. This means that disposal of soil containing any traces of knotweed requires disposal at licensed landfill sites-you may be prosecuted if you do not. In addition, you could also now be prosecuted under the Anti-social Behaviour, Crime and Policing Act 2014 if you have Japanese knotweed or other invasive plant growing on your property, and you do nothing to control it.

The powers conferred by the Act (although it does not explicitly refer to Japanese knotweed or other, similar invasive plants) makes it an offence if “individuals are acting unreasonably and persistently or continually act in a way that has a detrimental effect on the quality of life of those in the locality”. Local councils and the police (in most cases it will be the local council) will have the power to issue Notices on offending landowners.

A Notice under the Act can be used to stop or prevent any behaviour that meets this legal test. The test is that the conduct of the individual or body is having a detrimental effect of a persistent or continuing nature on the quality of life of those in the locality, and that the conduct is unreasonable. A Notice under the Act can be used to require someone to control or prevent the growth of Japanese knotweed or other plants that are capable of causing serious problems to communities.

What if Japanese knotweed is growing close to your property and the land owner is doing nothing about it? The 2014 Act has, for the first time, given you the means of protecting your property. Under section 57 of the Act, “conduct” includes “a failure to act”. The Notice can place restrictions on a person’s behaviour (in the case of an individual, as long as they are aged 16 or over) and, if necessary, force them to take steps to rectify the behaviour that is having a detrimental effect on the quality of life of the community. This means if an individual, or organisation, is not controlling Japanese knotweed or other invasive plant and could be reasonably expected to do so, the Notice could be used after a mandatory written warning has been served beforehand to get them to stop the anti-social behaviour.

The Notice will state what behaviour or action is having a detrimental effect on the quality of life of those in the local community. The requirement(s) set out in the Notice could include a requirement to stop a specified action or behaviour, a requirement to make reasonable efforts to make good any outstanding issues within a specified period of time and/or a requirement to take reasonable steps to prevent future occurrence of the problem. Breach of any requirement of a community protection Notice without reasonable excuse is a criminal offence, subject to a fixed penalty Notice (which attracts a penalty of £100) or prosecution. On summary conviction, an individual would be liable to a level 4 fine. An organisation, such as a company, is liable to a fine not exceeding £20,000.

Although an individual or an organisation cannot exercise these powers themselves, they do have the right to exercise a “community trigger” to get agencies to deal with a persistent or previously ignored anti-social behaviour problem. This could also apply to Japanese knotweed or other invasive plants. Agencies (including local authorities and the police) now have a duty to undertake a case review and consider what action they can take to resolve the problem when someone activates the trigger and their case meets a locally defined threshold. Where the threshold has not been met, local agencies can still carry out a case review based on factors such as the persistence of the problem, the harm or the potential harm caused or the adequacy of response from agencies.

Japanese knotweed-a new Act you can use to protect your property