Kahili ginger (Hedychium gardnerianum) and Yellow ginger (H flavescens)
Progressive Control Pests
(Photos courtesy Weedbusters)
These two species of Wild Ginger share many of the same features. The leaves of both species are wide and smooth and both grow up to 2 metres high or more, producing massive, branching rhizomes that can form a dense layer up to 1 metre thick, preventing any regeneration. Both species are frostsensitive, but their shade-tolerance allows them to grow under an overhead canopy, which provides protection from light frosts. These plants have invaded indigenous forest and regenerating shrublands in the North Island and in coastal areas at the top of the South Island. However, Kahili Ginger produces lemon-yellow flowers with red centre stamens in late summer and early autumn that generate fertile seed. Yellow Ginger produces cream-coloured flowers in late autumn and early winter but does not produce seed.
Reasons for the Strategy
Wild Ginger species are popular garden plants that have escaped and invaded large areas of indigenous forest and coastal margin in many parts of New Zealand. The plants can suppress indigenous regeneration by up to 90%. They can block streams and drains, and restrict access to recreation and conservation areas. Once established, the plants are extremely difficult to control.
Wild Ginger is assessed at “3” on the infestation curve for the Golden Bay to Kaiteriteri areas and “6” for the rest of the Tasman-Nelson region. Wild Ginger is well distributed throughout most of the Tasman-Nelson region but has a much more limited distribution around Golden Bay to Kaiteriteri. The low incidence of Wild Ginger in the Golden Bay to Kaiteriteri areas, extensive areas of suitable habitat, high natural values of these areas, and the potential for it to cause significant adverse effects, mean the benefits of progressive control far outweigh the costs.
To reduce the distribution and density of Wild Ginger in the Golden Bay to Kaiteriteri areas during the term of the Strategy.
The alternative option of “do nothing” or relying on voluntary control will not achieve the objective of reducing the distribution and density of Wild Ginger in the Golden Bay to Kaiteriteri areas, and will result in significant additional costs to the community with respect to lost natural values, and the increased cost of control in the future. Requiring progressive control throughout the region would not be cost-effective given the widespread distribution of Wild Ginger outside the Golden Bay to Kaiteriteri areas.
Strategy Rule for Wild Ginger
An occupier in the Golden Bay to Kaiteriteri areas shall destroy all adult and juvenile forms of Wild Ginger on land that they occupy. A breach of Strategy Rule 5.14.5 is an offence under Section 154(r) of the Biosecurity Act 1993.
Biosecurity Act Requirement
No person shall knowingly sell, propagate, breed, release, or commercially display Wild Ginger, under Sections 52 and 53 of the Act.