Japanese Knotweed

Japanese Knotweed (Fallopia japonica) is a fast growing perennial plant that has no native predators in the UK, and can regenerate from tiny fragments of material (0.7 grammes in the case of roots). Since its introduction as a “must have” plant on Victorian estates in the mid-nineteenth century (it thrived anywhere, including poor ground), it has become a serious nuisance in the wild, displacing native plants and their associated wildlife. Due to its deep-rooted nature (up to 7m horizontally from the crowns and 4m deep) its is very difficult to completely excavate or kill with herbicide, and unless comprehensively treated, will soon recover and resume being a problem.

Its frequent presence on development sites, resistance to quick eradication, wide root spread, and ability to regenerate from tiny fragments makes it a unique challenge that if not dealt with properly, opens both contractors and developers to the risk of prosecution. If you have time (at least a year) its always better to eradicate Knotweed on site before you start work.

The Legal Position

Japanese Knotweed is one of over 40 plants listed in Schedule 9 Part II of the Wildlife & Countryside Act 1989, which makes it a Section 14(2)(a) offence to “plant or otherwise cause (Japanese Knotweed) to grow in the wild”. The penalties for a Section 14 offence were modified by the Countryside & Rights of Way Act 2000, and a magistrates’ court can now impose a fine of up to £5000 on conviction, a six month prison sentence, or both.

The legislation applies to both deliberate and accidental spreading, and sites contaminated with Japanese Knotweed need to be carefully controlled to avoid breaches and potential Regulatory action. (This includes disposal of Knotweed waste at a site not licensed to receive it.) However, it should be noted that the legislation applies to “spreading” – it is not currently illegal to have Japanese Knotweed growing on your land providing you don’t spread it into the wild and it doesn’t cause a nuisance to neighbours (although the latter is a civil liability rather than criminal offence).

Dealing with Japanese Knotweed

The Environment Agency has produced a Knotweed Code of Practice which sets out the actions expected of Developers and Contractors when dealing with Japanese Knotweed on site.

Disposing of Japanese Knotweed, and soil contaminated with Japanese Knotweed roots

Due to its ability to regenerate from tiny fragments of viable material after a dormancy of up to 20 years, soil and waste containing Japanese Knotweed is considered to have the potential to cause “ecological harm”, and as such is considered to be a Controlled or Directive waste under the Waste Management Licensing Regulations 1984. As such, the producers of Knotweed waste have obligations for its proper treatment under the Waste Duty of Care, including ensuring that it is only disposed of at a site which has an appropriate permit to receive it. (Note – as the material has to be buried at a depth of 5m or more, not all “non-hazardous” sites are able to receive it – permits should be carefully checked.)

With regard to the description of the waste on the Waste Transfer Note (WTN), the Environment Agency have previously advised that the materials for disposal should be segregated on site and the following LOW Regs 2005 codes used with the bold additions to the descriptions clearly stated on the WTN:

  • Japanese Knotweed vegetation – 20 02 01 “Biodegradable waste containing Japanese Knotweed
  • Soils contaminated with Japanese Knotweed roots – 17 05 04 “Soils and stones other than those mentioned in 17 05 03* containing Japanese Knotweed

Do you suspect you have Japanese Knotweed on your site? – Give me a call! Looking for a training course on Invasive Plants? – Check out my Wildlife & Biodiversity Masterclass



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