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Management programme
Eradication.
Objectives
Reduce the level of infestation of purple loosestrife within the Waikato region to zero density to prevent adverse effects and impact.
Impacts
Economic, biodiversity, water quantity/quality

Native to Europe, Asia, North Africa and Australia it was first recorded in the wild in New Zealand in 1958. Large infestations in North America are causing huge damage to wetlands, completely altering food chains, causing flooding and blockages by trapping sediments. Purple loosestrife has also started to encroach on drier sites such as pasture and cropping land.

Close up of purple loosestrife

What does it look like?

Size

Attractive, erect, perennial herb up to 1m tall (but can grow taller).

Stems

Wooden square stems, smooth or hairy.

Flowers

Numerous magenta flower spikes seen December to February.

Roots

Grows from extensive root system that is very dense and wooden.

Seeds

Seeds in autumn.

Where is it found?

Invades wetlands, lakesides, streams, swamps, bogs that are damp in winter and drier in summer, and creeps onto dry margins.

Why is it a pest?

  • Purple loosestrife is a highly aggressive invader of wetlands.
  • Forms massive, tall, impenetrable stands, excluding all other species.
  • Able to dominate wetland and food sources for many fish and bird species.
  • Prevents access for wetland birds and recreational users, and out-competes native vegetation, reducing biodiversity.
  • A single mature plant can produce over two million seeds per year.
  • Seeds are fertile in the soil for up to three years.

How does it spread?

Seed is spread by the movement of water and contaminated machinery, soil, livestock and hay.

Responsibility for control

Waikato Regional Council is responsible for the control of purple loosestrife within the Waikato region. If you think you’ve seen it, call us – don’t try to control it yourself.

All persons shall inform Waikato Regional Council of the presence of purple loosestrife in the Waikato region, within five working days of the presence first being suspected (rule PLS-1 of the Waikato Regional Pest Management Plan 2022-2032) and to liaise with Waikato Regional Council in areas where control programmes are in place.

If purple loosestrife is present on a property that is to be subdivided or developed, there are additional rules and requirements that apply under section 6.6 of the RPMP 2022-2032.

Purple loosestrife is banned from being sold, propagated, distributed, or included in commercial displays.

Neutral

How do you get rid of it?

Purple loosestrife is exceedingly difficult to control. Please do not attempt to control it. Let us know if you think you have seen this plant or have it on your property by calling 0800 800 401 to report it to your local biosecurity pest plant officer.

More information

Publications 

The following publications are available for download or from Waikato Regional Council. Contact us to request a copy (freephone 0800 800 401).