( /ˌmɛləˈljuːkə/) is a genus of plants in the myrtle family Myrtaceae known for its natural soothing and cleansing properties. There are well over 200 recognised species, most of which are endemic to Australia. A few species occur in Malesia and 7 species are endemic to New Caledonia. The species are shrubs and trees growing (depending on species) to 2–30 m (6.6–98 ft) tall, often with flaky, exfoliating bark. The leaves are evergreen, alternately arranged, ovate to lanceolate, 1–25 cm (0.39–9.8 in) long and 0.5–7 cm (0.20–2.8 in) broad, with an entire margin, dark green to grey-green in colour. The flowers are produced in dense clusters along the stems, each flower with fine small petals and a tight bundle of stamens; flower colour varies from white to pink, red, pale yellow or greenish. The fruit is a small capsule containing numerous minute seeds.
Melaleuca is closely related to the genus Callistemon, the main difference between the two is that the stamens are generally free in Callistemon but grouped into bundles in Melaleuca. Callistemon was recently placed into Melaleuca.
In the wild, Melaleuca plants are generally found in open forest, woodland or shrubland, particularly along watercourses and the edges of swamps.
The best-accepted common name for Melaleuca is simply melaleuca; however most of the larger species are also known as tea tree, and the smaller types as honey myrtles, while those species in which the bark is shed in flat, flexible sheets are referred to as paperbarks. The Tea tree is presumably named for the brown colouration of many water courses caused by leaves shed from trees of this and similar species (for a famous example see Brown Lake (Stradbroke Island)). The name “tea tree” is also used for a related genus, Leptospermum, also in Myrtaceae.
One well-known melaleuca, Melaleuca alternifolia, is notable for its essential oil which is both anti-fungal, and antibiotic, while safely usable for topical applications. This is produced on a commercial scale, and marketed as Tea Tree Oil.
In Australia, Melaleuca species are sometimes used as food plants by the larvae of hepialid moths of the genus Aenetus including A. ligniveren. These burrow horizontally into the trunk then vertically down.
Melaleucas are popular garden plants, both in Australia and other tropical areas worldwide. In Hawaiʻi and the Florida Everglades, Melaleuca quinquenervia (Broad-leaved Paperbark) was introduced in order to help drain low-lying swampy areas. It has since gone on to become a serious invasive species with potentially very serious consequences being that the plants are highly flammable and spread aggressively. Melaleuca populations have nearly quadrupled in southern Florida over the past decade, as can be noted on IFAS‘s SRFer Mapserver