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: | Purple loosestrife |
Scientific name: | Lythrum salicaria |
Management programme: | Unwanted organism |
If you have seen or suspect the presence of this pest you must report the sighting to us.
Contact Otago Regional Council on 0800 474 082 or biosecurity@orc.govt.nz
Purple Loosestrife is a highly invasive perennial herb that forms dense stands in wetlands, along riverbanks, and in other aquatic habitats. It outcompetes native vegetation, disrupts water flow, alters nutrient cycling, and can degrade habitats for wildlife, particularly wetland birds. The plant can block access to waterways, impact irrigation systems, and reduce the quality of hay and pasture due to its unpalatable nature. Purple Loosestrife is a prolific seed producer, with each plant capable of producing up to 2.5 million seeds annually, which can be dispersed by wind, water, and contaminated machinery, making it difficult to control once established.
Purple Loosestrife is locally established in Oamaru, with scattered populations in Tapanui and Dunedin. The plant is found in low incidence across the region, primarily in wetland and riparian habitats.
It is an offence to breed, knowingly communicate, exhibit, multiply, propagate, release, or sell, an unwanted organism (Biosecurity Act 1993).
Follow up treated areas three times per year. Encourage natural regeneration of native plants or replant treated areas where possible after two to three treatments to establish dense ground cover and minimise reinvasion.
Dig out.
Plant parts requiring disposal: All parts.
Contact your local council for appropriate disposal locations.
No qualifications: Foliar spray with 100ml glyphosate per 10L of water.
Certified handler/experienced agrichemical user: Foliar spray with 100ml glyphosate per 10L of water and 20ml penetrant.
Caution: When using any herbicide or pesticide please read the label thoroughly to ensure that all instructions and safety requirements are followed.
Biological control is currently not available for this species.
You must notify the Otago Regional Council if you suspect the presence of this organism.
If you think you've seen Purple loosestrife: