Quick Facts

Quick facts

  • 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.

What Does It Look Like?

What is it?

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.

Flower colour

White, Pink

Growth form (weed type/habit)


Where it currently grows? Preferred habitat

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).

Are there similar species?

There are no native or other naturalised species in Australia that are similar to Koster's Curse (Navie 2004).

Why Is It A Weed?

What are its impacts?

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).

Native ecosystems: 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).

How does it spread?

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).

What is its history in Australia?

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).

How To Manage It?

Best practice management

Koster's Curse is one of the species targeted for national eradication under the National Resource Management Ministerial Council's National Cost-Sharing Eradication Programmes. These programmes map and monitor the full distribution of the species, and coordinate or undertake activities to eradicate that species from Australia.

Non-chemical control: Manual control: Manual weeding of Koster's Curse may be effective in small populations but it is important to eradicate plants before fruit set. In areas where there is an established seed bank follow-up work, for up to ten years, is necessary (Gerlach 2006).

Chemical control: Koster's Curse is susceptible to a number of herbicides but will regenerate unless further applications are made (Gerlach 2006).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au .

Difficulty of access to populations may prevent control by both manual weeding and spraying.

Does it have a biological control agent?


When does it grow? (lifecycle/growth calendar)

This information has not been recorded for Koster's Curse in Australia, but in tropical climates elsewhere it appears that flowering and fruiting may occur throughout the year, with continuous flowering being observed in areas where the rainfall exceeds 2 500 mm per year and there is no dry season. In areas with rainfall as low as 1 000 mm per year and where there is a dry season plants do not flower or fruit much once the dry season has commenced. Leaves fall off and shoot tips may die off before the onset of the next wet. Studies have also revealed that seeds can remain dormant for up to four years (Gerlach 2006).

Where Is It Found?

Which states and territories is it found?


What areas within states and territories is it found?

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).

Where does it originate?

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).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?


Where is it a declared weed?


Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?


Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?


Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Clidemia hirta

Other scientific names (synonyms)?

Melastoma hirtum L.

Does it have other known common name(s)?

Soap Bush, Soapbush, Hairy Clidemia

Blackberry – a community-driven approach in Victoria

Blackberry the weed (Rubus fruticosus aggregate) was first introduced to Australia by European settlers in the mid-1800s as a fruit. It was recognised as a weed by mid-1880s. Blackberry is a serious issue across Australia. It is estimated that blackberry infests approximately 8.8 million hectares of land at an estimated cost of $103 million in annual control and production losses.

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