Community help needed to find and weed out pest plant

22 July 2011

The Ministry of Agriculture and Forestry (MAF) and the Waikato Regional Council are calling on Hamilton residents to help them locate any further infestations of an invasive weed pest recently located on two adjacent residential properties.

The vine Chinese knotweed (Persicania chinensis) is a vigorous climber with the ability to smother native plants, forest areas and horticulture operations. The plant puts out a deep and wide network of roots, enabling it to spread rapidly. It is also suited to a range of environmental conditions.

The weed was discovered in two home gardens in the Chartwell area of Hamilton by a scientist who reported it to council biosecurity officer Darion Embling.

“We have moved rapidly to contain and get rid of this pest. All plants found at the two addresses have been treated with a herbicide and further treatments will be applied to ensure this robust plant is fully destroyed,” Mr Embling says.

The council is working closely with MAF in the careful management of the infestation. MAF spokesperson David Yard says key to full eradication of this aggressive plant from New Zealand is ensuring that all outbreaks of it are found and treated.

“We’re talking to the property owners concerned to gain some picture of how the weed may have got into their gardens and also to attempt to trace any other locations that the plant may be present.

“When we know where a pest like this is, we can do something about it. This plant is a known pest elsewhere in the Pacific and we want to stop it spreading any further here,” Mr Yard says.

“We urge people to call us if they think they have Chinese knotweed on their property. We recommend that they do not try to control it themselves. This plant is likely to be spread through fragments breaking off and re-sprouting into new plants, or on contaminated garden tools, so people treating it themselves could accidentally spread it further.”

Chinese knotweed plants grow to 70 cm to 1 metre tall in open ground, but are aggressive climbers that smother trees and other structures. Stems are pinkish in colour and leaves are generally soft textured, serrated edged and 4-16cm long. Chinese knotweed flowers in autumn. Its flowers are cream/pink and grow in clusters at the end of leafed stems.

To report suspected sightings contact MAF on 0800 80 99 66.

Full information about Chinese knotweed is at:

Photos of the plant are available on request.

Biosecurity Month

The New Zealand Biosecurity Institute, of which MAF and the Waikato Regional Council are members, has designated July as Biosecurity month. The response to the Chinese knotweed incursion is a good example of central and local government working together on biosecurity protection for New Zealand’s primary industries and the environment.

Media contacts:
MAF - Lesley Patston 04 8940163 or 029 8940163
OR call the MAF media phoneline: 029 894 0328

Waikato Regional Council – Karen Bennett 07 859 0922 or 021 791 995


Last Updated: 22 July 2011

Contact MPI

for general enquiries phone

0800 00 83 33