The ORC’s Environmental Data Portal is experiencing high traffic volumes affecting its effectiveness at present. The site is being worked on at present and people are asked to be patient. Please be considerate in using this tool, some people require access to the EDP for important decision-making today.
Environmental Data PortalThe ORC’s Environmental Data Portal is experiencing high traffic volumes affecting its effectiveness at present. The site is being worked on at present and people are asked to be patient. Please be considerate in using this tool, some people require access to the EDP for important decision-making today.
Common name: | Great willowherb |
Scientific name: | Epilobium hirsutum |
Management programme: | Unwanted organism |
If you have seen or suspect the presence of this pest you must report the sighting.
Report the sighting to Biosecurity New Zealand at 0800 80 99 66.
Great willowherb is a highly invasive flowering weed that rapidly establishes in wet or damp environments, including wetlands, lakesides, riverbeds, and roadside ditches. It forms dense stands that crowd out native vegetation, disrupt natural ecosystems, and alter water flow. The plant spreads mainly by seed, which can be dispersed by wind, water, contaminated machinery, and footwear. Its thick rhizomes can also regenerate when disturbed, making it difficult to control. If left unmanaged, Great willowherb can cause significant damage to wetland habitats and biodiversity.
Currently, Great willowherb has not been detected in Otago, but it is established in Canterbury, where it has been found in wetlands and lakesides. Surveillance in Otago is crucial to prevent its spread, particularly in high-risk areas like wetlands and other damp environments where it could establish and outcompete native species.
Great Willowherb is most visible when flowering from December through April.
It is an offence to breed, knowingly communicate, exhibit, multiply, propagate, release, or sell, an unwanted organism (Biosecurity Act 1993).
Do not attempt to undertake control of great willowherb yourself. Notify Biosecurity NZ at 0800 80 99 66.
You must notify Biosecurity NZ if you suspect the presence of this organism.
If you think you've seen Great willowherb: