The invasive tree privet is this month's poster plant for Weed Action Whangarei Heads.

In case anyone in the area isn't familiar with the "putrid tree", also known as Japanese privet or broadleaf privet, Weed Action has hung pink tape on roadside specimens along Whangarei Heads Rd.

The shrub which is unwanted for its potential to muscle out native trees as much as for the asthma and allergies it triggers, is on Weed Action's "dirtiest dozen" list.

"If we do nothing, over time it will spread more and more rapidly around the Heads, and replace our native forest with a monoculture of privet trees, as it has already started to do in spots further up the peninsula," the group's project co-ordinator Joanna Barr said.

"The leaves and fruit are poisonous, and the pollen and perfume contribute to allergies and asthma. It is extremely uncool."


Tree privet is fast-growing and long-lived, with prolific seeds that can be spread by birds or soil transfer, and it is tolerant of sun or shade. Axes and poison are among the arsenal recommended to kill it.

The action group is funded through the targeted weed rate of $50 a year imposed by Northland Regional Council on 2060 rateable properties at Whangarei Heads.

Part of that pays for Weed Action to help communities and private landowners exterminate targeted weeds, while the majority of the rate goes toward kiwi protection.

Ms Barr said the money enables the group to educate people as well as provide equipment to property owners.

''A lot of the roadside stuff - the coloured tape and signs - is a way of getting people who are not familiar with what are actually weeds to switch on to them,'' Ms Barr said.

''But it's all very well to get people to recognise the weed plants and the threat they pose, it's another to give them the tools they need to do their part. We're all about removing barriers to action.''

That includes the group running a community store where people are - literally - given tools, including herbicides.

Ms Barr said there were weeds on the ''dirtiest dozen'' list that were not part of the group's focus because they could only be picked at without much impact.

''People are pottering away in their own backyards but we need community buy-in to actually stop the spread of stuff like tree privet, which is fairly limited to one major infestation at the moment around Solomons Point, but they are spreading further out into the Heads.''

Other plants the group has given the ribbon and poster treatment, as well as a hands-on eradication drive - are moth plant (also known as kapok vine, moth vine, milk vine, milk weed and wild choko vine) and woolly nightshade (tobacco weed).