November's plants of the month
This month we feature two plants: the native New Zealand jasmine, or kaihua; and the pest plant Japanese honeysuckle.
… New Zealand jasmine / Kaihua - Parsonsia heterophylla
Last month we featured the invasive jasmine (Jasminum polyanthum), but did you know that New Zealand has its very own native ‘jasmine’? While not a true jasmine, also known as kaihua, these beautiful endemic vines have dark green leaves and produce small sprays of tiny white bell-shaped flowers during spring and summer. The flowers are gently scented, which attract native moths and potentially birds for pollination.
Read on to find out more about this lovely vine and how it can be used as a replacement for invasive menaces like Japanese honeysuckle.
… Japanese honeysuckle - Lonicera japonica
As beneficial as New Zealand jasmine is for our gardens and natural areas, Japanese honeysuckle is the opposite. It is a voracious grower, creating dense thickets of overlapping vines, smothering native plants and stopping natural regeneration. It does best at forest margins and around wetlands and rivers, which means these areas may be affected for years without action. Unfortunately for our native plants they cannot compete with this fast grower and, without control, honeysuckle can dominate an area, reducing native biodiversity.
More on native New Zealand jasmine or Kaihua
Kaihua is not actually related to any of the introduced jasmines in New Zealand, but like their name-sake, New Zealand jasmine flowers are fragrant. The vines can be used in garden plantings over a trellis or screen, as well as up big trees to create texture and variety, as well as extra habitat for native wildlife. They can grow quite vigorously and can help to keep back pest plants, but copes with being clipped into shape and will grow back.
The scientific name of kaihua - heterophylla - means ‘varied leaves’. This name was given to the plant because their juveniles have a range of different leaf shapes that are quite different to the adult plants. This can make it challenging to identify at the seedling stage.
Kaihua is actually related to the introduced swan plant, which supports monarch butterflies. New Zealand jasmine is thought to be primarily moth pollinated, although the use of flowers as a lure for birds by early Māori indicates that birds may also act as pollinators. Like many of our native plants, our jasmine are attractive to browsing possums, so animal pest control will help keep your plants healthy and lush.
Features of kaihua (NZ jasmine)
Flowers are small, white, bell-shaped and grow in clusters, gently scented
Vigorous vine, best grown on a strong support
Leaves are irregularly shaped and coloured in juveniles and dark green and glossy in adult vines
Attracts moths and possibly birds - if you have kaihua near you, look out for animals visiting the flowers
Seed pods look like green beans and split to reveal wind-dispersed fluffy seeds
Mature vines can eventually develop a vine base that is as thick as a sapling and can be mistaken for a tree at ground level
The threat from Japanese honeysuckle
At forest edges and around wetlands, Japanese honeysuckle can establish quickly and become very difficult to remove. The dense network of vines it can form, compete with native plants and can stop them growing. Our native birds and other wildlife rely on those native plants to thrive.
Why is Japanese honeysuckle a problem?
Once established, can quickly spread over large areas (aim to control small areas as soon as possible)
Forms dense thickets of overlapping vines
Can grow stems up to 15m in length in a single season
Smothers native and garden plants
Can dominate wetland areas
Prevents natural regeneration and seedling growth
Spreads through animal distribution of seeds and dumped vegetation
Tolerates wide range of conditions
Features of Japanese honeysuckle
Long, tough, wiry stems
Vines twist in a clockwise direction
Stems hairy when young, woody as they get older
Leaves grow in opposite pairs along the stems
Flowers area two-lipped yellow-white and distinctive
Flowering season September-May - look out for the flowers now!
Controlling Japanese honeysuckle
Unfortunately only cutting back honeysuckle will often promote thicker growth, but will slow it down. If it is cut back then a second method of control should be used as a follow-up, such as digging up the roots or herbicide application.
Dig out all root material and remove all stems - repeat in a 2-3 months time to remove any regrowth.
Glyphosate-based herbicide gel* e.g. Bamboo Buster, can be used on small patches by smearing thinly on the underside of leaves close to the ground. This method has had mixed reports in terms of effectiveness however, so must include a follow up.
For large areas
Spraying with glyphosate-based herbicide* is reported to be very effective - this should only be done with training, the correct equipment, and if on public land only with the correct certification. On private land ensure all safety advice is followed and spray drift is kept to a minimum.
Spot spray method - Cut all stems near ground level (keep cut stems off teh ground) followed in 1 to 2 months by spot-spraying of the regrowth with a glyphosate-based herbicide*
*Herbicide use: read all labels and follow all instructions carefully to ensure effective and safe application.
For roots that have been dug up you can:
Place in your landfill waste collection
Leave in a container of water until the roots have rotted
Place in heavy duty weed composting bag until rotted
See all our pest plant disposal information on our website.
What can you do to help?
Promoting native plants and reducing pest plants helps support our native birdlife and other wildlife.
Plant or encourage New Zealand jasmine or other native climbers and vines on your property, and remove pest vines like Japanese honeysuckle and common ivy.
Talk to your neighbours about Japanese honeysuckle and kaihua, or share this article.
Join a local restoration group or attend a restoration event in your area.
Tell people about the PFK Community Toolshed where they can borrow equipment and tools to help tackle Japanese honeysuckle and other pest plants.
How can you help restore Kaipātiki?
Recognise - Learn to recognise different pest plants and native plants
Report - Report locations where pest plants are damaging native plants or entering native bush
Remove - Find out how to control pest plants and get supplies from our Community Toolshed
Restore - Plant natives to stop pest plants coming back and to support our native wildlife.
If you want help with native plant restoration or any other pest plants, get in touch and we can help.
Find more information about pest plants on our other pages: