New invasive weed that could threaten native wetland plants found growing in New Zealand

May 9, 2018
Invasive weed great willowherb (Epilobium hirsutum).

The invasive weed, great willowherb (Epilobium hirsutum) has been found growing in New Zealand.

The weed has been positively identified at five sites in Canterbury, Biosecurity New Zealand (MPI) has confirmed.

MPI says initial discoveries occurred in and around the lake at Pegasus township in the Waimakariri District, and near the Kate Valley landfill, approximately 40km north of Lake Pegasus.

They say a field team is currently searching all likely places in the wider area to determine the extent of the incursion.

"We're in the early stages of determining the severity of this incursion," says John Brightwell, team manager, response at MPI.

"Once we've determined this, we'll work closely with Environment Canterbury and the Department of Conservation to develop an appropriate response." 

Great willowherb is characterised by its aggressive growth, and there is concern it may crowd out native wetland plants.

It can form dense stands, impeding water flow in waterways and wetlands. It may also spread to undisturbed damp areas and invade existing vegetation.

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