Wild ginger has thick fleshy stems and large waxy leaves. It reaches two to three metres in height and forms dense clumps. Wild ginger inhibits the growth of other plants by smothering them and stopping seedlings from establishing. It is a serious threat to native forests in the Waikato region. Find out about the two types of wild ginger that are pests in the Waikato region and check out our tips for control.
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Why wild ginger is a pest
Wild ginger is a serious threat to native forests in the Waikato region. It forms dense clumps in native forests, smothering young plants and preventing native seedlings from establishing. If left unchecked, wild ginger could permanently replace some of our native plants.
Wild ginger grows from large, fleshy underground stems called ‘rhizomes’. Clumps of rhizomes can form huge impenetrable mats under the soil surface, up to one metre deep. These thick mats of rhizomes make it very difficult for other plants to grow.
Above ground, wild ginger has thick fleshy stems and large waxy leaves. It grows to a height of two to three metres, forming a dense canopy that shades out smaller plants and seedlings.
Many new infestations of wild ginger come from dumped garden waste. The largest infestations within the Waikato region occur on the Coromandel Peninsula and on the West Coast between Raglan and Mokau.
How to recognise wild ginger
There are two types of wild ginger in New Zealand:
- kahili ginger (Hedychium gardnerianum)
- yellow ginger (Hedychium flavescens).
Both species are native to India and were introduced to New Zealand as flowering garden plants. Although both species have flowers, only kahili ginger is able to set seed in New Zealand. The seeds are spread by birds, making kahili ginger the worst weed of the two.
Identifying Features
Kahili ginger
- Stems up to two metres tall.
- Lemon-yellow flowers with red stamens – on a flower head 25 to 45 centimetres long.
- Flowers are strongly perfumed.
- Flowers from January to March.
- Up to 100 red seeds produced per flower head.
- Large waxy leaves, arranged alternately along a stem.
Yellow ginger
- Taller than kahili ginger - stems up to three metres high.
- Smaller creamy yellow-white flowers on a cone-like flower head.
- Flowers from May to June.
- Does not produce seed.
- Leaves are narrower and more upright.
Responsibility for control
Wild ginger is scattered throughout the Waikato region and is classed as a ‘containment pest’, requiring the removal of all plants (total control). All landowners/occupiers are responsible for the control of wild ginger on their property and are required to work with Environment Waikato in areas where control programmes are in place. Wild ginger is also banned from sale, propagation, distribution or commercial display.
How to control wild ginger
Both ginger species spread quite slowly, so systematic eradication is possible over large areas. When removing kahili ginger, remove the flower heads before spraying or removing the whole plant. This won’t kill the plant but will stop if from seeding that year. Burn the seed heads.
There are two main ways to control wild ginger:
- physical control
- herbicide control.
Only small infestations of wild ginger can be eradicated using physical control. Larger areas will need to be sprayed with herbicide.
Physical Control
- Pull out small seedlings by hand and dispose of them carefully.
- Dig out small clumps and remove all of the root system. Dispose of rhizomes by placing them in a black plastic bag and leaving them to rot. Or place the rhizomes in a weak herbicide mix, then crush, dry and burn them.
Herbicide Control
There are two main methods for herbicide control:
- cut stump treatment
- spray application.
Cut stump treatment
Slash the stems of larger plants horizontally near the roots. Immediately apply herbicide to the stems and roots with a paintbrush, eyedropper or small squeeze bottle. Leave the plants in the ground until the roots have dried off.
If you are using the herbicide Vigilant® and the plant has more than four rhizomes per shoot:
- Drill a hole (10 millimetres across) into every fourth rhizome. Make sure you drill down about three quarters of the way through the rhizome.
- Fill the hole with Vigilant®.
Spray application
Best results are achieved from spring to late autumn.
- Totally cover the foliage and roots until they are wet but not dripping. Be careful not to spray desirable plants. Do not remove the leaves or stems until they have gone brown and dried out (three or four months).
Alternatively,
- Cut and remove all stems and leaves and rake away ground litter to expose the rhizomes. Spray the rhizomes with herbicide and cover with leaves. The plant will take 12 to 15 months to fully die and rot. This method is particularly suitable for densely covered steep banks.
When using herbicides:
- Always read the instructions on the manufacturer’s label closely.
- Always wear protective clothing.
- Always minimise the risk to desirable plants.
- Contact the supplier for further advice.
Disclaimer: Although this content has been prepared in good faith from a number of sources believed to be reliable, Environment Waikato does not give any warranty that all information contained is accurate or complete, or that advice given will be appropriate in all circumstances. Mention of product trade names implies neither endorsement of those products nor criticisms of similar products not mentioned.
Follow-up management
After initial control, it’s important to:
- revisit the site at least annually to control re-growth
- stop weeds from invading by replanting with desirable plants (preferably natives) once re-growth is no longer a problem.
Summary of herbicides and application methods for control
When using herbicides:
- read the instructions on the manufacturer's label closely
- always wear protective clothing
- always minimise the risk to desirable plants
- contact the supplier for further advice.
| Herbicide |
Application |
| Escort® |
Cut stump treatment |
| |
Knapsack application |
| |
Handgun application |
| Vigilant® |
Cut stump treatment |
Further information
For further information and advice contact your local Biosecurity Plant Pest Contractor.
Related publications
Visit our Waikato Regional Pest Management Strategy.
'What makes a pest a pest? - A guide to Waikatos pest management future' download (730 kb, 104 seconds to download, 56k modem) Pick up, or order for free from our offices.
Pick up or order 'Plant me instead - Plants to use in place of common pest plants' for free from our offices.
Download the National Pest Plant Accord.
Pick up or order 'Poisonous plants and fungi in New Zealand - A guide for parents, schools and child minders' for $15 from our offices.