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Published: 2003-01-13 00:00:00

Coromandel residents and visitors should keep a lookout for the invasive pest wild ginger which is rife in the area.

Wild ginger forms dense colonies in native forests, smothering young native plants as well as preventing native seedling establishment and if left uncontrolled could result in the destruction of the entire forest. It is a serious threat to native forest, bushlands and coastal areas.

Wild ginger, both yellow and kahili, is native to India, introduced into New Zealand as ornamental garden plants. Wild ginger was widely cultivated by gardeners, but has since ‘escaped’ and invaded large areas of indigenous forest, coastal areas, and stream and river edges.

It is a perennial plant and thrives in well lit, moist warm areas and is also very shade tolerant. An adult plant can grow up to two metres in height and produces large wax covered leaves on thick stems. Kahili ginger flowers from February to April, while yellow ginger flowers in late autumn to early winter.

Kahili ginger can produce over 100 seeds per flower head and is spread by seed dispersal and people illegally dumping ginger roots on roadsides or in bush.

Wild ginger grows from large, branching tuberous roots which spread outwards and entwine to form a mat up to one metre deep. The largest infestations of wild ginger in the Waikato occur on the Coromandel Peninsula, and on the West Coast between Raglan and Mokau.

All land owners/occupiers are responsible for the control of wild ginger on their property. However where effective control is difficult - large infestations or where access is impeded - Environment Waikato may help land owners/occupiers develop and carry out control programmes.

Both species are total control plant pests over the entire Region, requiring the removal or control of all plants. Sale, propagation or distribution of either species is prohibited. Flower heads should be disposed of in the rubbish but their removal will not kill the plant, just stop it seeding.

Digging plants out can be effective for small stands, provided all the root system is removed and disposed of safely at an authorised refuse station (where it will not be used for compost). Few chemicals control wild ginger, however repetitive application in successive years with suitable herbicide can be very effective, Environment Waikato says.