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Sustainable Options Pest Plant Control Wild Ginger (Hedychium gardnerianum and Hedychium flavescens) Introduction There are two species of wild ginger, kahili ginger (Hedychium gardnerianum) and yellow ginger (Hedychium flavescens). Both species can form dense colonies in native forests, smothering young native plants as well as preventing native seedling establishment. This leads to the alteration of the structure of native forest and may result in the total death of the forest. Origin Kahili ginger is a native of India, growing on the lower slopes of the Himalayas, while yellow ginger originates in eastern India and Madagascar. Both gingers have been cultivated in New Zealand gardens since 1865, but it was not until the 1940s that kahili ginger was officially recorded as growing wild. Pest Plant Status In the Bay of Plenty region wild ginger is classified as a Progressive Control Pest Plant. (Refer Environment Bay of Plenty’s Regional Pest Management Strategy.) Land occupiers are required to control wild ginger on their properties. Assistance may be available from Environment Bay of Plenty by way of approved programmes. It is banned from sale, propagation and distribution within New Zealand. Description The wild gingers are herbaceous perennial plants. This means Kahili ginger has been a popular ornamental garden plant that their life-spans extend for more than two years and they do not accumulate woody tissue. Wild ginger grows from large, branching rhizomes. These large bulbous roots produce vertical stems annually. Beds of living rhizomes can form a dense layer up to a metre thick. Adult stems reach a maximum height of two metres and produce large wax covered, ovate alternate leaves (20 to 45 cm long and 10 to 15 cm wide). Yellow ginger leaves tend to be a little narrower than kahili ginger leaves. Individual kahili ginger flowers are lemon yellow with conspicuous red stamens and are displayed in large composite flower heads (12 to 45 cm in length), from February to April. Red seeds (1.5 to 1.8 cm long) are produced by kahili ginger during the autumn and winter months, with more than 100 seeds per flowerhead. Seed production tends to decrease as light levels decline under the forest canopy. Yellow ginger flowers are cream to light yellow in colour and come out in the late autumn/early winter period. The flowers are displayed in smaller composite flowerheads Kahili ginger flower head than those of kahili ginger. Yellow ginger flowers do not produce seed. Invasion Both wild gingers spread outwards along the ground by way of rhizomes, with new stems sprouting annually. New plants may develop also from rhizome portions which have become detached from the parent plant. The major source of this spread is by the illegal dumping of wild ginger rhizomes on roadsides or in bush. Kahili ginger is also spread by birds, eating and dispersing seeds away from the original infestations. Control Methods Manual Kahili ginger flowers can be cut and dropped on the ground prior to the seeds being formed. If seeds are present put the flower heads into a bag for disposal Working with our communities for a better environment 02 Wild Ginger (Hedychium gardnerianum Sustainable Options Pest Plant Control Yellow ginger flower head A Kahili Ginger seedling in native bush with the household rubbish. Flowerhead removal will not kill the plant but it will stop it seeding. Digging is an effective method of removing small stands of wild ginger, providing all the roots are removed intact and disposed of safely at an authorised refuse transfer station. CAUTION: Be careful not to spray desirable neighbouring plants. Herbicide • Metsulfuron-methyl (e.g. Escort®, Meturon®) Knapsack: 5 grams / 10 litres water plus 10 ml penetrant (e.g. Pulse®) Handgun: 25 grams / 100 litres water plus 100 mls penetrant (e.g. Pulse®) There are two application methods using the above herbicide: 1 Overall Spraying Ensure complete coverage of the plants. Wait until leaves and stalks have browned off (which may take several months) before removing them. This method is suitable for large infestations. 02 Metsulfuron-methyl is active in the soil and may be absorbed by the roots of neighbouring plants, possibly killing them. 2 Cutting and Spraying Cut off the leaves and stems and immediately spray the cut stems and rhizomes. This method means less herbicide is used and there is less chance of spray drift. It is preferable to use this method for smaller infestations where ginger plants are close to desirable plants or if the ginger is very tall. Information in this fact sheet regarding herbicides does not necessarily appear on the labels of the products concerned. Environment Bay of Plenty does not accept liability for any damage that may arise from use of chemicals at non-standard rates. Mention of product trade names implies neither endorsement of those products nor criticism of similar products not mentioned. Hedychium flavescens) Escort® herbicide applied to recently cut ginger rhizomes. Apply herbicide under low pressure and avoid runoff into the soil CAUTION: When using any herbicide READ THE LABEL thoroughly to ensure that all instructions and safety requirements are followed. For further information and advice, contact your local pest plant officer at Environment Bay of Plenty: Telephone: 0800 ENV BOP (368 267) Facsimile: 0800 ENV FAX (368 329) Pollution Hotline: 0800 73 83 93 Email: [email protected] Website: www.envbop.govt.nz Address: 5 Quay Street, P O Box 364, Whakatane, New Zealand This fact sheet was prepared by Environment Bay of Plenty’s Pest Plant Section. This factsheet was last updated March 2005 Working with our communities for a better environment