Melaleuca can reach 25 meters in height and grow to 90 centimeters in diameter. It is easily recognised by its spongy flaking bark (white, cream, orange-cream, fawn-grey or dark grey in colour (Craven, in press), lanceolate five-veined leaves, and clusters of woody seed capsules (Laroche 1999). Its white papery bark resembles birch and its white flower clusters resemble bottlebrush (Gioeli & Neal 2004). Its white tufted inflorescences are indeterminate, two to five centimeters long and arranged in bottlebrush-like spikes (Holliday 1989, in Center et al. 2006). Flowers of M. quinquenervia, like most Myrtaceae, have numerous stamens on a cup-shaped hypanthium surrounding the ovary. Myrtaceae leaves are simple and entire and the plants are usually aromatic (Laroche 1999); some have an intense citrus-like or eucalyptus oil odour when crushed (FLEPPC Undated).Within the spike-like inflorescence, flowers are clustered in threes; and secrete nectar, which collects within the base of the hypanthium; the stamens are arranged in five bundles each bundle consisting of five to ten fused stamens; the petals and filaments are usually white or creamish (Laroche 1999, L. Craven, pers. comm.). The capsular fruits, 2.7-4mm long, may persist for several years (Meskimen 1962, in Center et al. 2006). Please see the Melaleuca Management Plan 1999) for botanical illustrations of M. quinquenervia (page 10).
M. quinquenervia is part of the broad-leaved Melaleuca leucadendra-complex, which contains 15 species that are endemic to the Australian-Tasmanian region (Craven 1999, in Wineriter et al. 2003). The name Melaleuca comes from the Greek, meaning black and white, presumably referring to the white bark, often charred black by fire (Debenham, 1962, in Turner et al. 1998).
In general, xeric communities such as scrub tend to be resistant, but not immune, to melaleuca invasion (Laroche 1999). Favourable moisture conditions are found in pine flatwood depressions and the broad ecotones where pine and dwarf pond cypress mix (Duever et al. 1986, in Munger 2005). Melaleuca is tolerant of fire, seasonal drought and seasonal flooding (see Gomes & Kozlowski 1980; Geary & Woodall 1990). Melaleuca can grow in sites that are nutrient-poor such as pine savannas or wet prairies (Woodall 1981) due to its ability to send vertical roots straight down to the water table (Munger 2005).
As observed in Florida, Pratt (2005b) suggests wetlands that experience moderate to short hydroperiods are the most vulnerable to invasion by melaleuca. Melaleuca invades disturbed land such as abandoned farmlands, depressions in stump-harvested pinelands, road/canal wetland construction sites, improved pasture, natural rangeland and urban areas (Duever et al. 1986, Myers 1983 1984, in Munger 2005). Undisturbed ecosystems can be resistant, but not immune to, melaleuca invasion (Ewel et al. 1976, in Laroche 1999); however, in south Florida melaleuca has invaded essentially every existing community (Laroche 1999).
In Australia melaleuca occurs on sand, sandy loam, sandstone, laterite over sand, silty soil and serpentine substrates (Craven, In press), in New Guinea on highly organic, alluvial clays and in New Caledonia on well-drained slopes, ridges in the uplands (Geary Undated) and on flat, poorly drained soils (L. Craven, pers. comm.). Melaleuca establishes best on sandy soils but it can survive on nearly any soil type in south Florida (Ewel 1986, Hofstetter 1991, in Munger 2005). It is commonly found in Everglades ecosystems characterised by high organic soils (Pratt et al. 2004) or limestone-derived soils (Geary & Woodall 1990). Although melaleuca is found in soils of high pH plants may perform better in slightly acidic soils (Kaufman 1999, in Munger 2005). Melaleuca in Hawaii grow well on calcareous beach sand and on soils derived from basalt ash and lava rock of pH 4.5–5.5 (Geary 1998, in Geary Undated). According to Woodall (1981) a map of soil pH cannot be used to predict melaleuca invasion.
In its native habitat melaleuca is found mainly from sea level to 100m, but occasionally at elevations of 1000m (Geary Undated). Most of southern Florida, where melaleuca readily invades, is less than 8m above sea level (Geary & Woodall 1990). In its native habitat mean annual rainfall ranges from 900–1250 mm; mean monthly temperatures range from 5°C –32°C and in the southernmost part of its range, a few light frosts occur per year (Geary Undated). Where frequent freezing temperatures become common, melaleuca becomes less invasive (Munger 2005).The tree grows successfully in its introduced range where rainfall is 5000mm and a winter maximum occurs (Geary 1998, in Geary Undated).
Principal source: Pacific Island Ecosystems at Risk (PIER).
Compiler: IUCN/SSC Invasive Species Specialist Group (ISSG)
Review: Dr. Lyn Craven, Principal Research Scientist Australian National Herbarium Australia
Publication date: 2010-10-04
Recommended citation: Global Invasive Species Database (2024) Species profile: Melaleuca quinquenervia. Downloaded from http://iucngisd.org/gisd/species.php?sc=45 on 02-11-2024.
Melaleuca is the most problematic invasive plant species in Florida because of its wide distribution range, prolific seed production and potential impact on human health (Fuller 2005). Melaleuca threatens the preservation of critical wildlife habitat in southern Florida including in the Florida Everglades National Park. Despite control efforts melaleuca still occurred in around 170 000 hectares of southern Florida in 1997, representing 6% of the total region (Bodle & Van 1999, in Rayamajhi et al. 2007; Laroche 1999).
Ecosystem Change: Melaleuca threatens the integrity of subtropical freshwater ecosystem processes in Florida (Dray & Center 1994, in Lopez-Zamora Comerford & Muchovej 2004) by altering soil chemistry, reducing de-composition rates and modifying hydrology and fire regime. Melaleuca also reduces species biodiversity and alters species composition.
Reduction in Native Biodiversity: Melaleuca forests provide limited food and habitat value for native wildlife and can reduce indices of native species in Florida wetlands by as much as 80% (Dray et al 2006; Bodle et al., 1994, O’Hare & Dalrymple, 1997, in Dray et al. 2009; Porazinska Pratt & Giblin-Davis 2007). Decreases in diversity of native plant biodiversity have also been linked with melaleuca in the Bahamas.
Habitat Alteration: Melaleuca is contributing to significant habitat loss in the Everglades National Park by converting fire-maintained sawgrass communities into Melaleuca forest (Turner et al. 1998, in Munger 2005).
Displacement: Melaleuca displaces pond cypress (Taxodium ascendens) (Myers 1975 1983, Ewel 1986, in Rayamajhi et al. 2008b), slash pine (Pinus elliottii) and sawgrass (Cladium jamaicensis) (Bodle et al., 1994, in Tipping et al. 2008).
Competition: Melaleuca is competitively superior to most native vegetation occurring in the Florida Everglades (Turner et al. 1998, in Pratt et al. 2005b). It is fire-adapted, herbivore-adapted and produces seeds and roots prolifically.
Inhibits the Growth of Other Species: Allelochemicals present in roots can have a detrimental effect on the soil biota (Porazinska Pratt & Giblin-Davis 2007).
Economic:Balciunas and Center (1991, in Serbesoff-King 2003) reported that by the year 2010, close to $2 billion would be lost due to the melaleuca invasion in southern Florida. Financial losses included $1 billion in tourism to the Everglades NP, $250 million in tourism to the rest of south Florida, $250 million in recreation, $250 million due to fires, $1 million in control efforts, $10 million due to loss of endangered species and $1 million to nursery growers.
Agricultural: In one study 18 economic arthropod pests were collected from M. quinquenervia (Costello et al. 2008).
Human Health: As melaleuca populations expand in southern Florida and the human population increases the risk of fire and loss of human life and property increases (Laroche 1999).
Modification of Hydrology: A stand of melaleuca may transpire more water than the sawgrass communities it replaces (Hofstetter 1991a, in Laroche 1999).
Modification of Fire Regime: Ground fires, high temperatures, rapid spread rates and abundant smoke, all present in burning melaleuca stands, present new risks for wildlife in the Everglades wetlands (Flowers 1991, in Laroche 1999).
Modification of Nutrient Regime: The rate of decomposition of melaleuca litter is slower than that of native plants (Van & Rayamajhi, Unpub. Data, in Rayamajhi et al. 2006b).
Current management methods for melaleuca include herbicides, manual removal of plants, prescribed fires and bio-control.
Preventative Measures: Preventative measures are the best form of weed control. Education on the potential threats posed by melaleuca on invaded ecosystems should be targeted at the nursery industry and the general public.
Monitoring and Mapping: Model projections suggest there is considerable scope for further invasion of melaleuca under current climate conditions, with the highest risk areas occurring in Southeast Asia, the Caribbean, South and Central America and the Gulf coast in southern USA.
Physical:\nMechanical removal using heavy equipment is not appropriate in most natural areas because of disturbances to soils and non-target native vegetation; however, this method of control can be applied along canal and utility rights-of-way (Laroche 1999).
Physical: Physical methods also include the use of prescribed fire and of flooding More information is needed on the timing of prescribed burning, and constraints to this method include impacts on non-target species, the triggering of mass seed release by trees and liability concerns (Turner et al. 1998).
Chemical/Herbicidal Control: Exotic woody vegetation is most frequently managed by herbicides (Laroche 1999). Hexazinone and tebuthiuron are most effective in the control of melaleuca (Laroche 1999), however, they are no longer allowed to be applied directly to water in Florida (Laroche 1998a, in Serbesoff-King 2003). Current chemical control recommendations for melaleuca include low volume applications of glyphosate for control of saplings, and aerial or individual stem (girdle) applications of imazapyr alone, or in combination with glyphosate for mature trees (Langeland and Stocker 1997, in Stocker 1999).
Biological control: The lack of a long-lived soil seed bank (Van et al. 2005, in Center et al. 2007) makes M. quinquenervia vulnerable to herbivore-mediated reductions in fitness and delays in reproductive maturation. As canopy-held seed banks continue to diminish over time (Pratt et al. 2005), seedling suppression is predicted to have long-term effects on plant density. Two bio-control agents, the Australian melaleuca snout weevil (Oxyops vitiosa) and the Australian melaleuca psyllid (Boreioglycaspis melaleucae), have been approved by the USDA for use against melaleuca (Cuba et al. 2003, Wineriter et al. 2003, in Gioeli & Neal 2004) and have been released in the field. Research is being conducted on at least six other potential bio-control agents, including leaf, stem tip, and flower bud feeders (Burrows & Balciunas 1997 1998, Turner et al. 1998, in Stocker 1999). \n
Legislative: Melaleuca is on both the United States’ Federal Noxious Weed List and the Florida Prohibited Aquatic Plant List (Class I Prohibited aquatic plant) (Florida Department of Environmental Quality). \n
Integrated management: As a result of the implementation of the integrated Melaleuca Management Plan 1999 almost 100 000 acres of natural area have been cleared of melaleuca (Laroche 1994).
The Areawide Management Evaluation of Melaleuca quinquenervia (TAME) aims to demonstrate the effectiveness of integrated control of melaleuca in invaded habitats in the United States and elsewhere.