Kangaroo Island
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Mirror bush (Coprosma repens)

Mirror bush (Coprosma repens)

Medium Risk Weed for Kangaroo Island

Mirror bush is an Alert weed for Kangaroo Island. Notify the Kangaroo Island Landscape Board. Early detection and control are the best way to prevent the next widespread weed. 

It is a declared plant for South Australia. 

THE SITUATION AND WHAT TO DO

Mirror bush (also known as Karamu) is an evergreen shrub or small tree native to New Zealand that has become an environmental weed in parts of southern Australia. It was introduced to Australia in the 19th century as a hardy ornamental hedge and coastal windbreak plant due to its tolerance of salt spray and wind.

In South Australia it has naturalised mainly in coastal districts, where it invades native vegetation such as dunes, coastal shrublands and woodlands. The species spreads primarily through seed dispersed by birds that eat the fleshy berries. Seeds may also spread through dumped garden waste or movement of soil containing seed.

Mirror bush is a declared weed in South Australia under the Landscape South Australia Act 2019 

On Kangaroo Island occasional and widespread infestations related to garden plantings have been found across the island with new infestations being found regularly. A significant effort is going in to find and control this emerging pest plant and protecting environmental sites and assets. You can help by:

  • Remove isolated plants before they produce fruit.
  • Prevent dumping of garden waste in bushland or coastal areas.
  • Control infestations early to protect native vegetation.
  • Monitor sites for seedlings after removal, as birds can reintroduce seed.
Mirror bush (Coprosma repens)

DESCRIPTION

  • Growth form: dense evergreen shrub or small tree typically 1–4 m tall, occasionally reaching up to 8 m in favourable conditions.
  • Leaves: leaves occur in opposite pairs, are thick and leathery, oval to oblong in shape, and very glossy dark green on the upper surface.
  • Flowers: small, inconspicuous greenish or cream flowers produced in clusters in the leaf axils. Male and female flowers usually occur on separate plants.
  • Fruit: fleshy orange to red berry-like drupes that develop on female plants and ripen mainly in summer.
  • Seed: seeds are contained within the fleshy berries and are readily dispersed by birds and other animals. Seed viability is moderate to high after passage through birds. Individual plants can produce many berries each season, often resulting in hundreds to thousands of seeds from mature shrubs.

IMPACTS

Mirror bush mainly impacts native vegetation rather than agriculture. It invades coastal habitats where it forms dense thickets that shade out and replace native shrubs and ground flora. These infestations can alter vegetation structure and reduce regeneration of native plant species. Its bird-dispersed seeds allow it to spread from garden plantings into nearby bushland.

CONTROL OPTIONS

Effective management relies on early removal and preventing seed production. Small plants can be hand-pulled or dug out, ensuring roots are removed. Larger shrubs are usually controlled by cutting the stem and applying herbicide to the stump. Herbicides containing glyphosate or picloram + aminopyralid can be used for cut-stump treatment in bushland and non-crop areas.

Follow-up monitoring is important because new seedlings may establish from bird-dispersed seed. 

Maintaining healthy native vegetation and avoiding planting mirror bush cultivars near bushland reduces reinvasion risk.

Biological control agents are not currently available for this species.

Permitted and on label herbicides and rates can be found on the PIRSA Weed Control Website.

DECLARATIONS

Mirror bush is declared under the following sections of the Landscape South Australia Act 2019:

  • 188(1) Prohibiting sale of the plant

FURTHER INFORMATION

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