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JAPANESE KNOTWEED
Practical Advice
DO NOT
- Disturb any ground within 7m of any visible knotweed
- Cut down, trash down or attempt to pull up knotweed
- Move knotweed infested soil into areas not already infested with knotweed
- Spread live knotweed vegetation to areas not already infested with knotweed
- Move plant or equipment from infested areas without thoroughly cleaning off all infested material first using a high pressure water cleaner, ensuring effluent runs to an already infested area
- Take any infested soil or knotweed vegetation off site unless by a registered waste carrier, and with appropriate “Duty of Care” Transfer Note identifying the waste as infested with knotweed
DO
- Familiarize yourselves with the extent of the knotweed infestation on site
- Prevent unauthorised access within 7m of any visible knotweed
- Seek professional help as early as possible - costs can escalate for Japanese Knotweed removal.
Japanese Knotweed - Info
Japanese Knotweed (Fallopia Japonica) is a highly invasive weed that can seriously delay, or at worst prevent development of knotweed infested sites. Japanese Knotweed has an extensive underground rhizome system potentially extending 3m deep and 7m laterally from the visible plant, which damages property, spreads rapidly and results in infested ground being classified as “controlled waste”.
You get spectacular spread of the plant by disturbing the soil, as fragments of rhizome weighing less than 1 gram will regenerate into new infestations, growing to a height of around 3m in only one growing season.
As a result knotweed infestations are increasingly found throughout the UK, Europe and America, and without any natural predators, the problem is escalating to the extent that DEFRA now estimate the cost of eradication within the UK to be between £1.5 - 2.6 billion.
“Japanese Knotweed is potentially a bigger and more costly barrier to site redevelopment than contaminated land”
The plant is listed under Schedule 9 of the Wildlife and Countryside Act 1981, making it an offence to cause or allow the plant to spread in the wild.
All parts of the plant, and any soil contaminated with the rhizome, are classified as “controlled waste” requiring all the “duty of care” requirements under the Environmental Protection Act 1990 to be met.
Knotweed does not respect property boundaries and causes many neighbour disputes. There is recourse under “nuisance” common law for those affected, but this is likely to be an expensive avenue to follow.
In the past “dig and dump” methods have been used, where the infested soil is excavated and disposed of in landfill sites. Due to the potential 7m lateral spread and 3m depth of the rhizome this results in considerable quantities of material being exported from site, which at a cost of about £100/m3 is prohibitive. This method does not always solve the problem, especially where knotweed grows near site boundaries, and should only be considered as a very last resort.
Japanese Knotweed Control (standard herbicide) techniques can take 3 years of repeat treatment, and even then viable rhizome may well exist. Re-growth could occur if the treatment does not destroy all rhizome.
For developers, the “dig and dump” or the control of Japanese Knotweed methods are certainly less than ideal.
Environet has been working since 1998 to devise solutions that is cost effective, environmentally sound, and provided with guarantees.