Myrtaceae, the Myrtle Family
This is an evergreen tree that can grow to 80 to 100 feet tall. The multi-layered, peeling bark may be white, orangish-tan or gray in color. The crown is typically slender with few branches. The alternately arranged leaves are narrowly lance-shaped (occasionally sickle-shaped), gray-green in color and leathery in texture. Each leaf has five (sometimes three or seven) relatively indistinct, parallel veins running lengthwise. The leaves have a strong eucalyptus-like aroma when crushed. New growth is often silvery pubescent. The white, cream or greenish-white flowers are arranged in groups of three to form bottlebrush-like spikes at the branch tips. The sepals and petals are obscured by the prominent stamens, which are arranged in five bundles, each consisting of five to 10 stamens fused at their bases. The fruit are cupuliform (cup-shaped), woody capsules approximately 3/8 inch wide, borne in dense clusters along the branches. The capsules, each of which contains hundreds of tiny seeds, may persist unopened for several years. Seeds may be released gradually as the capsules desiccate or suddenly in response to fire, frost or injury to the tree.
Melaleuca is native to New South Wales and Queensland, Australia, as well as New Caledonia and Papua New Guinea. It is widely cultivated in tropical regions and has naturalized in southern Africa, India, the Philippines, the West Indies, Central America, Guyana, Hawaii, Louisiana and Florida.
This species is found in central and southern Florida counties. Melaleuca's impact is most profound in the Everglades, where it forms dense stands that severely impact the ecosystem by altering water flow, displacing native plant species and reducing habitat and food sources for wildlife. Although it is most commonly thought of as an invader of wetlands, melaleuca has been found in a variety of habitats in Florida, including scrub, sandhills, mesic to wet flatwoods, coastal hammocks, marshes, lakes, mangroves, coastal strands and disturbed lands.
Melaleuca is most likely to be confused with bottlebrush (Callistemon spp.), which has several cultivated species and one naturalized species in Florida. Melaleuca can be distinguished by its stamens fused in five bundles, each bundle positioned opposite a petal; the stamens of Callistemon are mostly free or unfused. In Florida, the cultivated or naturalized species of Callistemon all have red flowers, while melaleuca flowers are white.
Melaleuca produces flowers and fruit year-round in Florida, and it is estimated that a single tree is capable of producing 20 million seeds per year. Seed is dispersed primarily by wind, but water, small animals and off-road vehicles may also play a role in dispersal.
Melaleuca was first introduced to Florida around 1886 as an ornamental, shade tree and windbreak. There were over a dozen independent introductions between the 1880s and the 1950s (Dray et al. 2006). In the 1930s, the U.S. Army Corps of Engineers planted it to stabilize levees on Lake Okeechobee, and seed was dispersed by airplane over the Everglades. By 1993, it was estimated to be infesting half a million acres in South Florida. Melaleuca was added to the federal noxious weed list in 1992.