''Melaleuca'' () is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of nearly 300

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...

s in the myrtle

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Myrtaceae Myrtaceae (), the myrtle family, is a family of dicotyledonous plants placed within the order Myrtales. Myrtle, pōhutukawa, bay rum tree, clove, guava, acca (feijoa), allspice, and eucalyptus are some notable members of this group. All ...

, commonly known as paperbarks, honey-myrtles, bottlebrushes or tea-trees (although the last name is also applied to species of '' Leptospermum''). They range in size from small shrubs that rarely grow to more than high, to trees up to . Their flowers generally occur in groups, forming a "head" or "spike" resembling a brush used for cleaning bottles, containing up to 80 individual flowers. Melaleucas are an important food source for nectarivorous insects, birds, and mammals. Many are popular garden plants, either for their attractive flowers or as dense screens and a few have economic value for producing fencing and oils such as "tea tree" oil. Most melaleucas are

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

, with a few also occurring in

Malesia Malesia is a biogeographical region straddling the Equator and the boundaries of the Indomalayan and Australasian realms. It is a phytogeographical floristic region in the Paleotropical kingdom. It was first recognized as a distinct region ...

. Seven are endemic to

New Caledonia New Caledonia ( ; ) is a group of islands in the southwest Pacific Ocean, southwest of Vanuatu and east of Australia. Located from Metropolitan France, it forms a Overseas France#Sui generis collectivity, ''sui generis'' collectivity of t ...

, and one is found only on Australia's

Lord Howe Island Lord Howe Island (; formerly Lord Howe's Island) is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, part of the Australian state of New South Wales. It lies directly east of mainland Port ...

. Melaleucas are found in a wide variety of habitats. Many are adapted for life in swamps and boggy places, while others thrive in the poorest of sandy soils or on the edge of saltpans. Some have a wide distribution and are common, whilst others are rare and endangered. Land clearing, exotic myrtle rust, and especially draining and clearing of swamps threaten many species.

Description

Melaleucas range in size from small shrubs such as '' M. aspalathoides'' and '' M. concinna'' which rarely grow to more than high, to trees like '' M. cajuputi'' and '' M. quinquenervia'', which can reach . (One specimen of ''M. cajuputi'' reached a height of .) Many, like '' M. lineariifolia'', are known as paperbarks and have bark that can be peeled in thin sheets, whilst about 20% of the genus, including '' M. bracteata'', have hard, rough bark and another 20% have fibrous bark. All are

evergreen In botany, an evergreen is a plant which has Leaf, foliage that remains green and functional throughout the year. This contrasts with deciduous plants, which lose their foliage completely during the winter or dry season. Consisting of many diffe ...

, and the leaves vary in size from minute and scale-like ('' M. micromera'') to long ('' M. leucadendra''). Most have distinct oil glands dotted in the leaves, making the leaves aromatic, especially when crushed. Melaleuca flowers are usually arranged in spikes or heads. Within the head or spike, the flowers are often in groups of two or three, each flower or group having a papery

bract In botany, a bract is a modified or specialized leaf, associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves in size, color, shape or texture. They also lo ...

at its base. Five

sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 Etymology The term ''sepalum'' ...

s occur, although these are sometimes fused into a ring of tissue and five

petal Petals are modified leaves that form an inner whorl surrounding the reproductive parts of flowers. They are often brightly coloured or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corol ...

s which are usually small, not showy, and fall off as the flower opens or soon after. The

stamen The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

s vary greatly in colour, from white to cream or yellow, red, or mauve with their yellow tips (the

anther The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

s) contrasting with their "stalks" ( filaments). The fruits are woody, cup-shaped, barrel-shaped, or almost spherical capsules, often arranged in clusters along the stems. The seeds are sometimes retained in the fruit for many years, only opening when the plant, or part of it, dies or is heated in a bushfire. In tropical areas, seeds are released annually in the

wet season The wet season (sometimes called the rainy season or monsoon season) is the time of year when most of a region's average annual rainfall occurs. Generally, the season lasts at least one month. The term ''green season'' is also sometimes used a ...

Etymology

The name ''Melaleuca'' is derived from the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

μέλας (''mélas'') meaning "dark" or "black" and λευκός (''leukós'') meaning "white", apparently because one of the first specimens described had fire-blackened white bark. The common name "tea tree" has been applied to species in the genera '' Leptospermum'', ''Melaleuca'', '' Kunzea'', and '' Baeckea'' because the sailors on the '' Endeavour'' used the leaves of a shrub from one of these groups as a replacement for tea ('' Camellia sinensis)'' during Captain

James Cook Captain (Royal Navy), Captain James Cook (7 November 1728 – 14 February 1779) was a British Royal Navy officer, explorer, and cartographer famous for his three voyages of exploration to the Pacific and Southern Oceans, conducted between 176 ...

's 1770 voyage to Australia.

Taxonomy

Starr 020803-0090 Melaleuca quinquenervia

The first known description of a ''Melaleuca'' species was written by Rumphius in 1741, in ''Herbarium amboinense'' before the present system of naming plants was written. The plant he called ''Arbor alba'' is now known as '' Melaleuca leucadendra''. The name ''Melaleuca'' was first used by

Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

in 1767. Many species previously known as ''

Metrosideros ''Metrosideros'' is a genus of approximately 60 trees, shrubs, and vines in the family Myrtaceae, mostly found in the Pacific region. Most of the tree forms are small, but some are exceptionally large, the New Zealand species in particular. The ...

'' were then placed in ''Melaleuca''. In Australia, ''Melaleuca'' is the third most diverse plant genus with up to 300 species. The genus '' Callistemon'' was raised by

Robert Brown Robert Brown may refer to: Robert Brown (born 1965), British Director, Animator and author Entertainers and artists * Washboard Sam or Robert Brown (1910–1966), American musician and singer * Robert W. Brown (1917–2009), American printmaker ...

, who noted its similarity to ''Melaleuca'', distinguishing it only on the basis of whether the stamens are free of each other, or joined in bundles. Botanists in the past, including

Ferdinand von Mueller Baron Sir Ferdinand Jacob Heinrich von Mueller, (; 30 June 1825 – 10 October 1896) was a German-Australian physician, geographer, and most notably, a botanist. He was appointed government botanist for the then colony of Victoria, Australia ...

and Lyndley Craven have proposed uniting the two genera but the matter is not decided. Evidence from DNA studies suggests that either ''Callistemon'' and some other genera be incorporated into ''Melaleuca'' or that at least 10 new genera be created from the present genus. In 2014, Lyndley Craven and others proposed, on the basis of DNA evidence and a lack of morphological support, that species in the genera '' Beaufortia'', '' Calothamnus'', '' Conothamnus'', '' Eremaea'', '' Lamarchea'', '' Petraeomyrtus'', '' Phymatocarpus'' and '' Regelia'' be transferred to ''Melaleuca''. The

World Checklist of Selected Plant Families The World Checklist of Selected Plant Families (usually abbreviated to WCSP) was an "international collaborative programme that provides the latest peer reviewed and published opinions on the accepted scientific names and synonyms of selected p ...

maintained by the

Royal Botanic Gardens, Kew Royal Botanic Gardens, Kew is a non-departmental public body in the United Kingdom sponsored by the Department for Environment, Food and Rural Affairs. An internationally important botanical research and education institution, it employs 1,10 ...

lists ''Calothamnus'' and the other genera as synonyms of the accepted genus ''Melaleuca''. The move has not been adopted by all Australian herbaria with some taxonomists, including Alex George opposing the move.

Distribution and habitat

Most melaleucas occur naturally only on the Australian mainland. Eight occur in

Tasmania Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...

, but only two are endemic to that island. One ('' M. howeana'') is endemic to

and seven are endemic to Grande Terre, the main island of New Caledonia. A few tropical species also occur in

Papua New Guinea Papua New Guinea, officially the Independent State of Papua New Guinea, is an island country in Oceania that comprises the eastern half of the island of New Guinea and offshore islands in Melanesia, a region of the southwestern Pacific Ocean n ...

, and the distribution of one subspecies, ''Melaleuca cajuputi'' subsp. ''cumingiana'' extends as far north as

Myanmar Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...

Thailand Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...

, and

Vietnam Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about and a population of over 100 million, making it the world's List of countries and depende ...

. The southwest of

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

has the greatest density of species, and in the tropical north of the continent, species such as '' M. argentea'' and ''M. leucadendra'' are the dominant species over large areas. Melaleucas grow in a range of soil types and many tolerate occasional or even permanent waterlogging. Some species, especially the South Australian swamp paperbark, '' M. halmaturorum'', thrive in saline soils where few other species survive. Many are fire tolerant, regenerating from epicormic buds or by

coppicing Coppicing is the traditional method in woodland management of cutting down a tree to a tree stump, stump, which in many species encourages new Shoot (botany), shoots to grow from the stump or roots, thus ultimately regrowing the tree. A forest ...

, but no melaleucas occur in rainforest and few species occur in the arid zone.

Ecology

Melaleucas are mostly pollinated by insects, including the introduced honey bee ('' Apis mellifera''), flies, beetles, wasps and

thrips Thrips (Order (biology) , order Thysanoptera) are minute (mostly long or less), slender insects with fringed wings and unique asymmetrical mouthparts. Entomologists have species description , described approximately 7,700 species. They fly on ...

. Birds such as lorikeets and

honeyeater The honeyeaters are a large and diverse family, Meliphagidae, of small to medium-sized birds. The family includes the Australian chats, myzomelas, friarbirds, wattlebirds, miners and melidectes. They are most common in Australia and New Gui ...

s as well as

bats Bats are flying mammals of the order Chiroptera (). With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most birds, flying with their very long spread-out ...

often visit the flowers and are probably also pollinators. Some species of ''Melaleuca'', especially '' M. alternifolia'', are cultivated for the production of tea tree oil, and in plantations are susceptible to a number of insect pests. The most significant of these is the chrysomelid '' Paropsisterna tigrina'', but other

beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...

s, cutworm caterpillars ('' Agrotis species''), psyllids, mole crickets ('' Gryllotalpa''), and others cause significant damage. More than 100 species of insects are known to feed on melaleucas. Native stands have fewer predators, but tea tree

sawfly Sawflies are wasp-like insects that are in the suborder Symphyta within the order Hymenoptera, alongside ants, bees, and wasps. The common name comes from the saw-like appearance of the ovipositor, which the females use to cut into the plant ...

('' Pterygophorus'' species) and longicorn beetles are often found. The scale insect '' Beesonia ferrugineus'' forms round, fluffy-looking galls on branches of several ''Melaleuca'' species. Melaleucas are also susceptible to myrtle rust ('' Puccinia psidii'') which can result in damage to soft plant material and the death of highly susceptible hosts. Myrtle rust is common in eastern Australia, including

and has been detected in the

Tiwi Islands The Tiwi Islands ( meaning "two islands") are part of the Northern Territory, Australia, to the north of Darwin, Northern Territory, Darwin adjoining the Timor Sea. They comprise Melville Island, Northern Territory, Melville Island, Bathurst I ...

Invasive species

Melaleuca quinquenervia ''Melaleuca quinquenervia'', commonly known as the broad-leaved paperbark, paper bark tea tree, punk tree or niaouli, is a small- to medium-sized tree of the myrtle Family (biology), family, Myrtaceae. It grows as a spreading tree up to tall, ...

'' (broad-leaved paperbark) is the most damaging of 60 exotic species introduced to the

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

Everglades to help drain low-lying swampy areas. Introduced in the early 20th century, it has become a serious

invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

, with damaging effects including the displacement of native species, reduction in wildlife habitat, alteration of hydrology, modification of soil, and changes in fire regimes. The tree's perseverance in the face of efforts to eradicate it has earned it the nickname "punktree".

Uses

Traditional Aboriginal uses

Aboriginal Australians Aboriginal Australians are the various indigenous peoples of the Mainland Australia, Australian mainland and many of its islands, excluding the ethnically distinct people of the Torres Strait Islands. Humans first migrated to Australia (co ...

used several species of ''Melaleuca'' to make rafts, as roofing for shelter, bandages, and food preparation. "Bee bread" and honey were collected from the hives of native stingless bees in melaleuca forests in the

Northern Territory The Northern Territory (abbreviated as NT; known formally as the Northern Territory of Australia and informally as the Territory) is an states and territories of Australia, Australian internal territory in the central and central-northern regi ...

. The Bundjalung people traditionally lived in the area of north-eastern

New South Wales New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...

where '' Melaleuca alternifolia'' is

, and they treated skin infections by crushing the leaves of that species over skin infections then covering the area with a warm mudpack.

Essential oils

''Melaleuca alternifolia'' is notable for its

essential oil An essential oil is a concentrated hydrophobic liquid containing volatile (easily evaporated at normal temperatures) chemical compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetheroleum, or simply as the ...

, which has

antifungal An antifungal medication, also known as an antimycotic medication, is a pharmaceutical fungicide or fungistatic used to treat and prevent mycosis such as athlete's foot, ringworm, candidiasis (thrush), serious systemic infections such as ...

and

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...

properties in vitro. Though it is safe for topical applications, tea tree oil is toxic if ingested orally. The oil is produced on a commercial scale and marketed as

tea tree oil Tea tree oil, also known as melaleuca oil, is an essential oil with a fresh, camphoraceous odour and a colour that ranges from pale yellow to nearly colourless and clear. It is derived from the leaves of the tea tree, '' Melaleuca alternif ...

. ''Melaleuca cajuputi'' is used to produce a similar oil, known as cajuput oil, which is used in

Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...

to treat a variety of infections and to add fragrance to food and soaps.

Horticulture

Melaleucas are popular garden plants, both in Australia and other tropical areas worldwide. The first to be cultivated were grown in England from seed in 1771. Some melaleucas are commonly cultivated, grown as trees for parks and large gardens (such as '' Melaleuca leucadendra'') or as ornamentals (sometimes as '' Callistemon'') such as '' M. citrina'' (''Callistemon citrinus''), '' M. hypericifolia'' and '' M. wilsonii''.

Melaleucas used in horticulture

Image:Melaleuca leucadendra-large1.jpg, '' M. leucadendra'' in the Royal Botanic Gardens, Sydney Image:Melaleuca pulchella 0217.jpg, '' M. pulchella'' ("claw flower") in Melbourne Botanic Garden Image:Melaleuca squarrosa.jpg, '' M. squarrosa'' in Langwarrin Flora and Fauna Reserve Image:Melaleuca elliptica 01.JPG, '' M. elliptica'' in Edinburgh Botanic Garden Image:Melaleucawilsonii1.jpg, '' M. wilsonii'' in San Diego Botanic Garden Image:Melaleuca pungens.JPG, '' M. pungens'' useful as a hedge because of its prickly foliage Image:Melaleuca hypericifolia.jpg, The widely cultivated '' M. hypericifolia'' in Arthurs Seat State Park Image:Melaleuca salicina (Nane Glen).jpg, '' M. salicina'' – a popular garden shrub Image:Melaleucalinariifolia.jpg, '' M. linariifolia'' (snow-in-summer).

In popular culture

Tea trees (spelled ''Ti-Trees'') are specifically mentioned in the lyrics of a short aria 'Joy' published around 1916 by J.D.Fletcher & Co of London, by Australian composer Arthur Chanter (1866-1950).

References

External links

* {{Authority control Myrtaceae genera Myrtales of Australia Rosids of Western Australia