Weeds in Australia


Clidemia hirta


Koster's Curse (Clidemia hirta) is a densely branching, long-lived shrub which is commonly 0.5-3 m tall but may reach as much as 5 m in shaded areas. Its branches and leaves are covered in large, stiff, brown or reddish hairs. The leaves are opposite, oval or egg-shaped in outline, 5-18 cm long, 3-8 cm wide, with finely toothed margins and a general wrinkled appearance. They have 5 prominent, almost parallel veins that run the length of the leaf blade. The upper surface of the leaf is less hairy than the lower surface.

The bristly flowers are small and white or occasionally pinkish and are arranged in small clusters in the leaf forks or at the tips of the branches. Each flower has 5 petals which are about 6-11 mm long and its stamens have a claw-like appearance. The fruit are globular, hairy berries 4-9 mm in diameter and dark blue, purplish or blackish when ripe. Each berry contains more than 100 brown seeds about 0.5-0.75 mm long (Navie 2004).

For further information and assistance with identification of Koster's Curse contact the herbarium in your state or territory.


In Australia, Koster's Curse is only known to have become naturalised near the town of Julatten in northern Queensland. At the time of its discovery steps were taken to eradicate the plants (Waterhouse 2003; Navie 2004).

Its potential distribution in Australia includes humid coastal sites in the Northern Territory and much of northeast Queensland (Waterhouse 2003).

Key points:
  • Koster's Curse (Clidemia hirta) is only known to have naturalised at one locality in Australia (Julatten, north Queensland). At the time of its discovery, steps were taken to eradicate the plants.
  • It is naturalised in many tropical countries, being a highly invasive species of both disturbed and undisturbed habitats.
  • It can form dense thickets that smother plantations, pastures and native vegetation, much like lantana.
  • In Hawaii, Koster's Curse infests more than 40 000 hectares and negatively effects native ecosystems.
  • The potential distribution of Koster's Curse in Australia includes humid coastal sites in the Northern Territory and much of northeast Queensland.
How it spreads:

Berries of Koster's Curse can be dispersed in water, but the most common method of dispersal is by birds. A mature shrub can produce thousands of berries, most of which end up being dispersed by birds. It has also been noted that in Hawaii Koster's Curse berries may be spread by vehicles, people and pigs (Waterhouse 2003; Land Protection 2005; Gerlach 2006).

Where it grows:

Koster's Curse prefers humid tropical climates and invades both disturbed and undisturbed habitats. In such areas in Australia it is a potential weed of pastures, roadsides, woodlands and rainforests (Navie 2004).

Flower colour:White, Pink
Distribution map:

Navie 2004


From knowledge of where this plant has naturalised overseas there seems no doubt that establishment of Koster's Curse in Australia would be highly undesirable. Koster's Curse can form dense thickets that smother plantations, pastures and native vegetation, much like lantana. It has the potential to cause significant damage to primary production as well as sensitive habitats and native plant communities, especially in the wet tropics (Land Protection 2005).

In Hawaii it infests more than 40 000 hectares and may be replacing endemic species that formerly predominated, threatening their extinction. The impact of this weed on native species and ecosystems is devastating and the rate at which it spreads throughout the islands is alarming (Gerlach 2006). It is a highly invasive shrub in the montane rain forests and cloud forests of Samoa, Fiji, Wallis and Futuna. In the Pasoh Forest Reserve on the Malaysian Peninsula competition with native species in forest gaps has the potential to alter forest regeneration. Koster's Curse is one of the most problematic invasive species in the Comoros Archipelago, Réunion, Mauritius and the Seychelles (Gerlach 2006).


Koster's Curse is a native of tropical America, extending from southern Mexico to northern Argentina and islands of the Caribbean. It is naturalised throughout much of the world's tropical and subtropical regions, including islands of both the Indian Ocean (e.g. Comoros Islands, Seychelles) and Pacific Oceans (e.g. Fiji, Hawaii and Papua New Guinea), the Indian subcontinent and eastern Africa (Gerlach 2006; PIER 2007).


Koster's Curse is believed to have spread from its natural range to other countries as the result of deliberate ornamental introductions. It was discovered for the first time in Australia in August 2001. A tiny infestation of at least several hundred plants was found at Julatten, north Queensland. Bird and flood-borne dispersal of seeds was evident, with mature plants and seedlings scattered throughout a former palm nursery and along the banks and bed of an ephemeral stream running through the property. The source and duration of the infestation have not been determined. Every observed plant of Koster's Curse was destroyed during a search of the area, but the characteristics of shade tolerance and bird-dispersed seed have increased the difficulty of detection of all plants (Waterhouse 2003; Gerlach 2006).


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