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Japanese Knotweed (Fallopia Japonica)

Japanese knotweed is the most pernicious terrestrial weed in Britain, causing a huge amount of economic and environmental harm. The IUCN lists it amongst the top 100 worst invasive plants in the world. It is now widespread throughout Britain, and has nearly doubled its distribution in the last 20 years.

Knotweed is difficult and expensive to eradicate because it proliferates from fragments as small as a little finger nail, can persist underground in a dormant state for years, and is extremely resilient to a range of conditions and herbicides. The cost of a development can increase by 10% if knotweed is present, because expensive techniques must be employed including deep burial, use of root barrier membranes, creation of bunds, transport to licensed landfill sites and repeated herbicide applications.

What harm does it do?

Economic: knotweeds can grow through tarmac and concrete, causing structural damage to buildings and surfaces, including flood defences. Stands impede water flow and floating dead stems can cause blockages, increasing flood risk.

Biodiversity: stands of Knotweed suppress native species by casting heavy shade, and producing long-lasting leaf litter. The loss of native species can increase riverbank erosion.
 
Amenity: access to watercourses, and along paths, is impeded. Knotweed also causes sociological problems by trapping litter and encouraging vermin.
 
Special restrictions: It is prohibited to plant, or allow the spread in the wild of this species (Sch9, Wildlife & Countryside Act). SEPA has set out guidelines for developers and others to avoid spreading Japanese knotweed. Prosecution could result if these aren’t followed. Japanese knotweed is not, as often thought, a notifiable weed. SEPA/EA does not have an obligation to control it: management of is the responsibility of the land owner/occupier, and must comply with SEPA/EA guidelines.

Wording courtesy of : http://www.invasivespeciesscotland.org.uk/


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