Updated: Aug 30, 2022
December's pest plants of the month
The invasive pair of tree privet and Chinese privet are a big problem in Kaipātiki. These tree species are fast growing and spread easily. Around our backyards and reserves they out-compete and outgrow native trees, forcing them out. Eventually they replace the native trees which support our native wildlife. And to add insult to injury they are a common cause of allergies due to the copious amounts of pollen they produce. Read on to learn more.
Deliberately introduced as ornamental plants or for use as hedging, they soon escaped people’s gardens and started growing almost everywhere, changing the native ecosystem in places.
Another interesting thing to mention in the story of introduced privet - the Privet lace bug. This small, easily over-looked insect has been assessed and cleared as a biological control on Chinese privet. In fact, some of these special bugs were released here in Kaipātiki and the distinctive signs of them feeding on privet has been seen in Birkenhead War Memorial Park. Take a walk there and see if you can spot them.
Chinese privet and tree privet are noticeable this time of year because of the large number of small flowers they produce. Typically, Chinese privet flowers September to December, and tree privet November to March.
Unfortunately birds, both native and introduced, will spread the seeds. This means these pest plants can be spread over a wide area easily and quickly. And each plant when mature can produce thousands of seeds, which germinate easily. You will almost always find seedlings under almost every mature privet.
Why are they a threat?
Our native birds and other wildlife rely on native trees to thrive. Privet is a highly invasive pest plant species, and as such will rapidly colonize empty areas and stands of trees, displacing any natives in the area. In areas where natives are regenerating, privet will easily take over, out-competing the natives in the process, eventually changing the ecosystem permanently.
How to identify it
Features of Tree Privet - see photos below.
Small to Large evergreen tree or shrub (less than 15 meters).
Pointed, green leaves that are glossy on top.
Distinctive lumpy warts on stems/trunks.
Creamy flowers make up the flower heads.
Flowering season typically November to March
Bluish purple-black berries.
Features of Chinese Privet - see accompanying photos:
Small evergreen tree or shrub (less than 5 meters).
Hairy shoots and warty lumps on older stems.
Oval, dull green leaves.
Very fragrant white flowers, arranged in drooping clusters.
Flowering season typically September to December.
Round green berries that turn to dull purplish-black.
What can you do about it?
Spread the word
Talk to your friends, whanau and neighbours about the threat from pest plants, show them this article, or tell them that Pest Free Kaipātiki have advice and resources to help.
Tell them about the PFK Community Tool Shed where they can borrow equipment and tools to help tackle pest plants.
Tackling pest trees like Chinese privet and tree privet help to support our native birds and other wildlife.
Getting rid of privet
Controlling privet can be easy when they are small plants, but becomes increasingly difficult as they get larger.
For large trees, think of the control and restoration as a longer process where you replace the privet with native trees over time. You can even remove the privet in stages, cutting off branches, while the native plants establish and grow underneath.
Pull or dig up seedlings and small plants, especially when ground is soft.
For large plants, cut down and dig out all the roots.
You can also try covering cut trunks with thick plastic sheet and mulch to prevent any light coming through - but this is not always successful.
Important: Cutting down privet without dealing with the roots will allow the tree to regrow - either dig out roots completely, or refer to the herbicide control methods below.
Cut the stump and paste with a herbicide gel called Metgel (see below).
For larger trees, ring bark the trunk and apply Metgel.
Bamboo buster is another herbicide gel option, but may not be as effective.
There are other method of control but they require certain level of experience or training. Get in touch if you want to learn more.
*Always read the labels when using herbicides and wear appropriate protective equipment where necessary.
Metgel and metsulfuron - Be very careful applying metsulfuron or Metgel near water bodies and near valued plants - only apply a very thin smear of gel on cut stems/trunks and do not allow the herbicide to drip on to other surfaces or soil.
Large trees that are closer than 1.5 times the height of the tree from paths, walkways and property must not be ringbarked or drilled. Trees over 4m must be dealt with by a qualified arborist.
Important: Whichever control method you use, always try to return after 2 or 3 months and look for regrowth.
For roots or seedlings that have been dug up you can:
Allow them to dry out and die
When dried and dead, they can be disposed of without risk of regrowth
For seeds that have been collected:
Try to contain them and avoid spreading them
Dispose of in waste to landfill
Drown in container of water for a few months until they rot
See all our pest plant disposal information on our website.
What can you plant instead?
If you have Chinese privet or tree privet on your property, please consider getting rid of it over time and planting native trees and shrubs to replace them. Good alternatives to the invasive privet trees are the following, which all help native animals:
Hangehange (Genistoma rupestre) - also known as New Zealand privet although it's not a true privet - very good as a tree or hedgerow
Houhere (Hoheria populnea)
Māpou, red matipo (Myrsine australis) - makes great hedging
Or any native tree that you like - any native plant will be better than Chinese or tree privet.
Check out these pages for lots more photos:
King's Plantbarn plantdoctor - privet
See section 30 of the Plant me instead booklet
How can you help restore Kaipātiki?
Recognise - Learn what pest plants and native plants look like
Report - Report locations where pest plants are damaging native plants or entering native bush
Remove - Find out how to control pest plant and get supplies from our Community Tool Shed
Restore - Plant natives to stop pest plants coming back and to support our native wildlife.
If you have an area of pest plants threatening an area of bush or reserve near you, get in touch and we can help.
Find more information about pest plants on our other pages: