Purple loosestrife

A tall, hairy herb often between one and two metres tall with dense spikes of purple flowers. It outcompetes native vegetation and blocks access to waterways.

Description

• Stems are woody with a pinkish base, and appear square on cross-section. It can produce up to 50 stems per root.
• Leaves are narrow, between 5-12cm long and sometimes covered in fine hairs.
• Large (20-25cm), hairy flower spikes are very distinctive between December – February when purple-magenta flowers appear.
• Seeds are minute, numerous and within blackish capsules. They are dispersed by wind, water, waterfowl and soil movement
• Vegetative spread from root fragments. Human-mediated dispersal can occur through the dumping of garden waste, deliberate plantings and movement of contaminated machinery, vehicles and clothing.
• Habitats include still or slow-moving water bodies, wetlands, riparian margins, lakes, ditches, and reservoirs.

What you need to know

Forms dense stands, outcompeting and displacing native vegetation. Impedes waterfowl and access to waterways.

Management approach

This is a declared pest managed under the Canterbury Regional Management Plan 2018 – 2038 (PDF file, 10.6MB) within the sustained control programme.

Sustained control

Pests in the sustained control programme vary greatly in their distribution across the region. Some are found in low numbers, while others are already well-established pests.

The intention of the sustained control programme is to reduce the impact on values and spread of a pest onto neighbouring properties.

The community should make us aware of any purple loosestrife plants in Waitaha/Canterbury. We will work with affected landowners to undertake control of purple loosestrife.

Purple loosestrife is also declared an unwanted organism by the Ministry for Primary Industries (MPI) because it is capable of causing harm to the natural environment, physical resources or human health in Aotearoa/New Zealand.

These species pose a high risk to our environment, economy, recreation, and cultural values.

Rules

Any species declared a pest cannot be sold or be in a place where plants are being sold. Pest plants cannot be propagated, bred, multiplied, communicated, released, caused to be released, or otherwise spread.

Control

Site management

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.

Physical control

Dig out.

Plant parts requiring: All parts.

Contact your local council for appropriate disposal locations.

Chemical control

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

Biological control is currently not available for this species.