Native Restoration is on a mission to create a Wattle Awareness Month, and there is no better time than the present as many pest-wattles bloom into flower during the month of July. Sadly, many home and landowners are unaware of these pest plants and how to correctly eradicate them from our precious environment. Native Restorations has created the perfect guide on how to identify and remove pest wattles, while also offering some wonderful native choices for replacement.
Wattles wattles everywhere! If you have taken a drive around New Zealand lately you may have noticed the bright yellow flowers beginning to bloom to life around roadsides. These not only cause issues for the allergy dwellers of this lovely land of ours, they can also spell disaster for our native bushlands. That’s right – the humble yellow flowering wattle is a well-known and distinct pest plant species.
What is a Native Plant in New Zealand?
Native plants in New Zealand are part of the unique flora that evolved in isolation over millions of years. This isolation has led to a high level of endemism, with about 80% of the country's plants found nowhere else in the world. Common native species include the manuka (Leptospermum scoparium), known for its white or pink flowers and the famous manuka honey, and the kowhai (Sophora species), renowned for its brilliant yellow flowers that attract native birds like tui and kereru.
Why are Pest Wattles So Bad?
Pest wattles, primarily invasive Australian species like Acacia dealbata (silver wattle) and Acacia mearnsii (black wattle), pose significant threats to New Zealand's ecosystems. Although these species are considered native ‘across the ditch’ here in NZ they cause endless problems. These species grow rapidly, outcompeting native plants for light, nutrients, and space. Their aggressive growth can lead to the displacement of native vegetation, altering habitats and reducing biodiversity. Pest wattles can also exacerbate fire risks and soil erosion, disrupting the ecological balance.
How to Identify a Pest Wattle in New Zealand
Silver Wattle (Acacia dealbata)
This species is recognisable by its feathery, silvery-grey foliage and bright yellow, globular flower heads. It typically flowers from late winter to early spring. Silver wattle can form dense thickets that outcompete native plants.
Black Wattle (Acacia mearnsii)
Black wattle has dark green, feathery leaves and clusters of small, yellow flowers. It can grow up to 20 meters tall and is known for its rapid growth and ability to spread quickly, forming dense stands that suppress native vegetation
Step-by-Step Guide to Killing Pest Wattle Trees in New Zealand
Effective eradication of pest wattle trees requires a combination of physical and chemical control methods. Follow these steps to ensure successful removal and prevention of regrowth;
Physical Control - Hand Pulling Young Wattle Trees
Target - Small, young wattle plants.
Method - Hand-pull or dig out the plants with minimal soil disturbance to remove the entire root system, preventing regrowth.
Cutting and Treating Older Trees
Target - Larger, established wattle trees.
·Method: Cut the tree trunk to ground level. Clear away any green growth around the stump. Immediately apply a suitable herbicide (e.g., metsulfuron-methyl 600g/kg at 5g/L or triclopyr 600 EC at 50ml/L) to the freshly cut stump to prevent regrowth.
Herbicide Control
Chemical Application Methods Include;
Ring Barking
Method - Remove a sleeve of bark approximately 15 cm wide around the entire circumference of the tree, down to the cambium layer (the white creamy layer directly under the bark).
Apply Herbicide - Apply herbicide to the exposed cambium layer.
Drill and Fill
Method - Drill downward-angled holes into the trunk, spaced evenly around the tree.
Fill with Herbicide - Fill each hole with herbicide. Note that this method can be hard on drills and batteries due to the hardwood nature of wattle trees.
Flitching with an Axe
Method - Use an axe to create notches or small reservoirs around the tree's circumference, deep enough to reach the cambium layer.
Apply Herbicide - Fill these notches with herbicide to ensure it penetrates the tree effectively.
Herbicide Recommendations
Metsulfuron-methyl - 600g/kg (5g/L)
Triclopyr 600 EC - 50ml/L for stump treatment, or 30ml/10L for spraying in spring-summer.
Glyphosate - 10ml/L for spraying in spring-summer.
Important Considerations
Safety - Always wear protective clothing, gloves, and eye protection when handling herbicides.
Environmental Impact - Follow local environmental guidelines to minimise the impact on surrounding vegetation and wildlife. Ensure you do not use herbicides during windy or raining conditions to prevent run off and exposure to the surrounding environment.
Persistence - Some wattle species are resilient, so repeated applications may be necessary to ensure complete eradication.
By following these steps, you can effectively remove and kill pest wattle trees, helping to protect New Zealand's native ecosystems.
Other Native Plants to Plant in Place of Pest Wattles
To restore and protect local ecosystems, consider planting native species that support biodiversity and ecological balance:
Pohutukawa (Metrosideros excelsa): Known as the New Zealand Christmas tree, it has bright red flowers and is excellent for coastal areas.
Kowhai (Sophora species): With its beautiful yellow flowers, it attracts native birds and supports local wildlife.
Harakeke (Phormium tenax): Commonly known as New Zealand flax, it is versatile and provides habitat for native insects and birds.
Hebe (Hebe species): These shrubs offer a variety of forms and flower colors, providing aesthetic appeal and habitat.
Nikau Palm (Rhopalostylis sapida): The only native palm in New Zealand, adding a tropical touch to gardens while supporting native fauna.
With information comes power particularly when it concerns increasing the native plant population and removing pest plant species. Sadly, many Kiwis are unaware that some plants – that may look attractive - are detrimental to our native plant species. This can have a terrible knock-on effect for our precious and exclusive wildlife in New Zealand.
At Native Restorations we’d love to see some examples of Kiwis embracing our incredible range of native plants! Head over to our Facebook page to share your images of how you are helping increase the native plant population in your garden or local areas.
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