Purple pest present on Banks Peninsula

Environment Canterbury is calling for reports of sightings of pest plant purple loosestrife on Banks Peninsula, following the discovery of a large new infestation in Prices Valley.

“The Prices Valley find is the first known large infestation on the Peninsula,” said Environment Canterbury regional leader biosecurity Graham Sullivan.

“We know purple loosestrife (Lythrum salicaria) rapidly invades damp ground and shallow water. When left uncontrolled, its dense bushy growth forms massive, tall, impenetrable stands that will outcompete our native species. Its ability to form monocultures changes a wetland and marginal habitats and food sources for many fish and bird species,” said Sullivan.

“We don’t want this for our region’s wetlands and watercourses.”

Left uncontrolled, purple loosestrife can form monocultures causing blockages and flooding.  Purple loosestrife produces millions of long-lived, highly viable seeds from an early age.  It can tolerate hot or cold conditions, and low to high nutrient levels in the water. Its seed is spread by the movement of water, contaminated machinery and soil.

Now is the optimum time to identify if you have purple loosestrife on your property.

Purple loosestrife What to look out for

  • A tall green perennial herb, that grows anywhere between 1-3m tall in summer.
  • It will have a taproot with many branched stems that feel square shaped when you rub them between your thumb and finger (4-8 sided stems).
  • Look for narrow leaves that are in pairs and alternate up the stem.
  • During the summer months (November to February), it will have showy, densely hairy flowerhead spikes.
  • The flower spike will be about 20-25 cm long, with purple-magenta flowers that have 5-6 petals.
  • Later in the season you may see blackish seed capsules (3-5mm long).
  • There are no similar species that grow this tall.

What to do if you find purple loosestrife

  • Take a photo of the suspected plant(s) and email it, along with the location of the sighting, to Gemma Livingstone at gemma.livingstone@ecan.govt.nz.
  • Alternatively, you can call 0800 EC INFO and leave your name, contact number, and the location of the suspected sighting.

Other information:

Environment Canterbury’s contractor completed one run of control along the Prices Valley drain prior to Christmas and will conduct another in late January/early February 2018.

Funding for the Prices Valley Control was gained through the Te Waihora flagship biodiversity project