Clidemia hirta
|
Taxon |
Family |
|
Clidemia hirta L. D. Don. |
Melastomataceae |
 |
 |
| C. hirta flowers and fruit Credit: Forest & Kim Starr, USGS |
Invading non-native habitat in Hawaii |
Common names: Koster's curse, soap bush, clidemia.
Synonyms: Melastoma hirta L., Melastoma hirsutum L.
Life form: Shrub
Biology/Ecology:
Dispersal: Seeds are dispersed short distances when eaten by birds, mongooses and pigs or attached to the fur of animals. Ornamental introductions by humans are probably the cause of the plant's spread to non-native regions.
Reproduction: Produces several white/pink flowers on axillary or terminal cymes. The plant is capable of producing over 500 berries per year, which are red/purple to blackish or dark blue. Each berry usually contains between 100 and 300 seeds, which are between 0.5 and 0.75 mm long. Flowering and fruiting occurs all year in wet environments with no dry season.
Herbivores: Many herbivores in its native range, including Liothrips urichi, commonly introduced as a biocontrol agent.
Resistant stages: Plant can resist drought for up to six months, seeds are viable for four years.
Habitat:
Native habitat: Dry to wet tropics, grows in understorey of forest, steep embankments and disturbed open areas such as roadsides, pastures and plantations.
Habitat occupied in invaded range: Disturbed forests and forest gaps, grassland, especially mesic and wet environments.
Habitat requirements:
| Altitude | Below 1500 metres above sea level. |
| Light | Shade to full sun |
| Temperature | No information available. |
| Annual rainfall | Wide range of rainfall tolerated (from 1000 to 7600mm), although the plant is more successful in areas of high rainfall. |
| Soil | No information available. |
Distribution:
Native to Central America and tropical regions of South America, Islands of West Indies.
Introduced range: Invasive in almost all Pacific and Indian Ocean Islands, South-east Asia and East Africa.
Impacts:
Ecosystem: Grows and spreads very quickly by producing many seeds, displacing plants found in shaded habitats. Rapidly invades disturbed habitats, often caused by feral pigs, altering natural forest regeneration by forming impenetrable thickets and developing monotypic stands. Has the ability to invade undisturbed habitats, although population levels usually remain low in this case. Can tolerate a wide variety of environmental conditions.
Health, social and economic: Rapidly grows along roads and trails in Hawaii, increasing maintenance costs. Disrupts grazing land and developing plantations, especially in Fiji. Rapid growth of thickets creates physical barriers to humans.
Management:
Mechanical: Rarely effective when conducted after first fruit set, but eradicating seed sources reduces the spread of the plant. Seedlings can be dug out. Small populations of the plant can be manually removed. Controlling the feral pig population may be effective, as there is often a link between feral pigs and C. hirta. Feral pigs cause disturbance in natural plant communities and spread the seeds of C. hirta. Limiting the disturbance of natural communities as much as possible will hinder the spread and damage caused by C. hirta.
Chemical: The shrub has often been reported as being fairly herbicide resistant. Glyphosate may be an effective foliar spray herbicide. 2,4-D amine and triclopyr at 0.7kg/ha have been very effective at controlling the plant in Southeast Asia. Continual monitoring and further applications should be made to prevent the plants regenerating.
Biological: Often the best option considering the vast areas often covered by C. hirta. The thrips Liothrips urichi has been shown to be successful at affecting growth in open sunny areas, but is less successful in shaded habitats. The thrips has had difficulty becoming established on the Solomon Islands. The fungal pathogen Colletotrichum gloeosporoides was released as a biocontrol agent in Hawaii in 1986 and has been effective at both killing C. hirta plants and spreading between them. So far the pathogen has only been effective in dry conditions. The beetle Lius peisodon has recently been released on Hawaii, and early results suggest that although the beetle has had little overall effect, it does attack plants in the shade.
References:
Weber, E., 2003. Invasive Plant Species of the World: A Reference Guide to Environmental Weeds. CABI Publishing, Wallingford, UK.
Cronk, Q.C.B., Fuller, J.L., 1995. Plant Invaders. Chapman & Hall.
Gerlach, J. and ISSG, 2005. Clidemia hirta (shrub). Global Invasive Species Database. Available from http://www.issg.org/database/species/ecology.asp?si=53&fr=1&sts=sss (Accessed August 2006).
Binggeli, P., 1998. An Overview of Invasive Woody Plants In The Tropics. School of Agricultural and Forest Sciences, University of Wales, Bangor. Available from http://www.bangor.ac.uk/~afs101/iwpt/welcome.shtml (Accessed August 2006).
Tunison, T., PRO, 1991. Element Stewardship Abstract for Clidemia hirta. The Nature Conservancy, The Global Invasive Species Initiative. Avialable from http://tncweeds.ucdavis.edu/esadocs/documnts/clidhir.html (Accessed August 2006).
Last updated October 2006
