Japanese and giant knotweed are already here but we're working to get rid of them.
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Japanese and giant knotweed are woody herbs which grow to around 2-4m high from rhizomes (fleshy underground roots). Their root system can be up to 3m deep and extend to 7m across.
Japanese knotweed and giant knotweed grow rapidly from an extensive fleshy underground root system, forming dense, long-lived thickets. They exclude other desirable species and prevent native seedlings from establishing.
Japanese knotweed and giant knotweed are spread through the movement of their roots or when shoots and roots are transported by people. They are very hardy plants and are difficult to eradicate. Originally from Japan, knotweed is a very serious invasive pest plant in parts of Europe. It grows primarily in disturbed areas, roadsides and river banks. Japanese knotweed and giant knotweed occur at sites in Taupiri, Karangahake (south Coromandel), and in Hamilton and Tamahere.
Waikato Regional Council is responsible for controlling Japanese and giant knotweed – do not attempt to remove them yourself. However, landowners/occupiers are encouraged to report Japanese and giant knotweed on their properties and liaise with Waikato Regional Council in areas where control programmes are in place. Japanese and giant knotweed are also banned from being sold, propagated, distributed or included in commercial displays.
If you see these weeds on your property, do not cut or treat them. Call 0800 BIOSEC (0800 246 732) to report them to your local biosecurity pest plant officer.
See our tips overleaf for ideas on how you can help us prevent Japanese and giant knotweed from spreading.
WARNING! Fragments as small as 0.7 grams can form new plants, so be extremely careful with any equipment used on site.
Japanese and giant knotweed can spread by soil movement, garden waste and equipment such as diggers and farm machinery. When disturbed, Japanese and giant knotweed breaks up easily into small fragments which can easily regrow. Take special care not to disturb it or transport it to new sites.
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