Japanese Knotweed is controlled in Japan naturally by a combination of fungus and insects. However, in the UK, there are no natural enemies for Japanese Knotweed and it outcompetes all our native species for light, water and nutrients.
The speed at which Japanese Knotweed has spread throughout Britain has been nothing less than spectacular. The damage it has already caused to commercial and domestic sites is practically unquantifiable and it now occupies a site in every 10km of England and Wales and is also present to a lesser extent in Scotland, Ireland and other parts of Europe.
The aggressive growth pattern means it is capable of exposing weaknesses in hard engineered structures such as concrete, tarmac, brick walls and foundations.
Specific problems caused by Japanese Knotweed are:
- Damage to paving and tarmac areas
- Damage to retaining wall structures
- Damage to building foundations
- Damage to flood defence structures
- Damage to archaeological sites
- Reduction in land values
- Aesthetic issues
- Reduction in biodiversity through out-shading native vegetation
- Many insects/wildlife that are dependent on our native plants are lost or in danger
- Restriction of access to riverbanks for anglers, bank inspection and amenity use
More recently, we have come across cases where the presence of Japanese Knotweed has caused problems such as the refusal of a mortgage or refusal from Local Authority to grant planning permission until it is eradicated.
Japanese Knotweed is now classed as "controlled waste" under the Environmental Protection Act 1990 and requires disposal at licensed landfill sites. It should never be included in normal household waste and 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.