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''Melaleuca'' () is a
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
of nearly 300
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...
of
plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae excl ...
s in the myrtle
family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
,
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 sp ...
, commonly known as paperbarks, honey-myrtles or tea-trees (although the last name is also applied to species of ''
Leptospermum ''Leptospermum'' is a genus of shrubs and small trees in the myrtle family Myrtaceae commonly known as tea trees, although this name is sometimes also used for some species of '' Melaleuca''. Most species are endemic to Australia, with the great ...
''). 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 A brush is a common tool with bristles, wire or other filaments. It generally consists of a handle or block to which filaments are affixed in either a parallel or perpendicular orientation, depending on the way the brush is to be gripped durin ...
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 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 found else ...
to
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
, with a few also occurring in Malesia. Seven are endemic to
New Caledonia ) , anthem = "" , image_map = New Caledonia on the globe (small islands magnified) (Polynesia centered).svg , map_alt = Location of New Caledonia , map_caption = Location of New Caledonia , mapsize = 290px , subdivision_type = Sovereign st ...
, 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 Po ...
. 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. Every species in the genus is an
evergreen In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm climates, and contrasts with deciduous plants, whic ...
, 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, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or o ...
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 The term ''sepalum'' was coine ...
s occur, although these are sometimes fused into a ring of tissue and five
petal Petals are modified leaves that surround the reproductive parts of flowers. They are often brightly colored or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corolla''. Petals are usuall ...
s which are usually small, not showy, and fall off as the flower opens or soon after. The
stamen The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the fila ...
s vary greatly in colour, from white to cream or yellow, red, or mauve with their yellow tips (the
anther The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filam ...
s) contrasting with their "stalks" (
filament The word filament, which is descended from Latin ''filum'' meaning " thread", is used in English for a variety of thread-like structures, including: Astronomy * Galaxy filament, the largest known cosmic structures in the universe * Solar filament ...
s). The fruit 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) is the time of year when most of a region's average annual rainfall occurs. It is the time of year where the majority of a country's or region's annual precipitation occurs. Generally, the sea ...
.


Taxonomy and naming

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 in 1767. Many species previously known as ''
Metrosideros ''Metrosideros'' is a genus of approximately 60 trees, shrubs, and vines mostly found in the Pacific region in the family Myrtaceae. 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 ''Callistemon'' is a genus of shrubs in the family Myrtaceae, first described as a genus in 1814. The entire genus is endemic to Australia but widely cultivated in many other regions and naturalised in scattered locations. Their status as ...
'' was raised by Robert Brown, 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, (german: Müller; 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 Vict ...
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 ''Calothamnus'' is a genus of shrubs in the family Myrtaceae and is endemic to the south-west of Western Australia. The common names one-sided bottlebrush or claw flower are given to some species due to their having the flowers clustered on on ...
'', '' Conothamnus'', '' Eremaea'', ''
Lamarchea ''Lamarchea'' is a genus of shrub in the myrtle family Myrtaceae described as a genus in 1830. The entire genus is endemic to Australia. ;Species # '' Lamarchea hakeifolia'' Gaudich. - Shire of Irwin in Western Australia # '' Lamarchea sulcata ...
'', '' 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) is an "international collaborative programme that provides the latest peer reviewed and published opinions on the accepted scientific names and synonyms of selected pla ...
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 1,100 ...
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. The name ''Melaleuca'' is derived from the
Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...
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 ''Leptospermum'' is a genus of shrubs and small trees in the myrtle family Myrtaceae commonly known as tea trees, although this name is sometimes also used for some species of '' Melaleuca''. Most species are endemic to Australia, with the great ...
'', ''Melaleuca'', '' Kunzea'', and ''
Baeckea ''Baeckea'' is a genus of flowering plants in the myrtle family, Myrtaceae, all but one endemic to Australia. Plants in the genus ''Baeckea'' are shrubs or small trees with leaves arranged in opposite pairs, white to deep pink flowers with five s ...
'' 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 James Cook (7 November 1728 Old Style date: 27 October – 14 February 1779) was a British explorer, navigator, cartographer, and captain in the British Royal Navy, famous for his three voyages between 1768 and 1779 in the Pacific Ocean and ...
's 1770 voyage to Australia.


Distribution and habitat

Most melaleucas occur naturally only on the Australian mainland. Eight occur in
Tasmania ) , nickname = , image_map = Tasmania in Australia.svg , map_caption = Location of Tasmania in AustraliaCoordinates: , subdivision_type = Country , subdi ...
, but only two are endemic to that island. One ('' M. howeana'') is endemic to
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 Po ...
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 (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...
, and the distribution of one subspecies, ''Melaleuca cajuputi'' subsp. ''cumingiana'' extends as far north as
Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...
,
Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...
, and
Vietnam Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making ...
. The southwest of
Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to t ...
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, 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 The western honey bee or European honey bee (''Apis mellifera'') is the most common of the 7–12 species of honey bees worldwide. The genus name ''Apis'' is Latin for "bee", and ''mellifera'' is the Latin for "honey-bearing" or "honey carrying", ...
''), flies, beetles, wasps and
thrips Thrips (order Thysanoptera) are minute (mostly long or less), slender insects with fringed wings and unique asymmetrical mouthparts. Different thrips species feed mostly on plants by puncturing and sucking up the contents, although a few are ...
. 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 G ...
s as well as
bats Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". 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 bir ...
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 The insects of the beetle family Chrysomelidae are commonly known as leaf beetles, and include over 37,000 (and probably at least 50,000) species in more than 2,500 genera, making up one of the largest and most commonly encountered of all beetl ...
, '' Paropsisterna tigrina'', but other
beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...
s, cutworm caterpillars ('' Agrotis species''), psyllids, mole crickets (''
Gryllotalpa ''Gryllotalpa'' is a genus of insects in the mole cricket family Gryllotalpidae. Species The ''Orthoptera Species File'' lists a number species, including cryptic species groups (indicated with a * and often distinguished only by song pattern ...
''), 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 ('' Pterygophorus'' species) and longicorn beetles are often found. 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
Tasmania ) , nickname = , image_map = Tasmania in Australia.svg , map_caption = Location of Tasmania in AustraliaCoordinates: , subdivision_type = Country , subdi ...
and has been detected in the
Tiwi Islands The Tiwi Islands ( tiw, Ratuati Irara meaning "two islands") are part of the Northern Territory, Australia, to the north of Darwin adjoining the Timor Sea. They comprise Melville Island, Bathurst Island, and nine smaller uninhabited islands, w ...
.


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, Myrtaceae. It grows as a spreading tree up to tall, with its trunk co ...
'' (broad-leaved paperbark) is the most damaging of 60 exotic species introduced to the
Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and ...
Everglades to help drain low-lying swampy areas. Introduced in the early 20th century, it has become a serious
invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species adv ...
, with damaging effects including the displacement of native species, reduction in wildlife habitat, alteration of hydrology, modification of soil, and changes in fire regimes.


Uses


Traditional Aboriginal uses

Aboriginal Australians Aboriginal Australians are the various Indigenous peoples of the Australian mainland and many of its islands, such as Tasmania, Fraser Island, Hinchinbrook Island, the Tiwi Islands, and Groote Eylandt, but excluding the Torres Strait ...
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 (commonly abbreviated as NT; formally the Northern Territory of Australia) is an Australian territory in the central and central northern regions of Australia. The Northern Territory shares its borders with Western Aust ...
. The Bundjalung people traditionally lived in the area of north-eastern
New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...
where '' Melaleuca alternifolia'' is
endemic Endemism is the state of a species being found 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 found else ...
, 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 o ...
which is both
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 bacterial infections, and antibiotic medications are widely used in the treatment and prevention ...
, while safely usable for
topical A topical medication is a medication that is applied to a particular place on or in the body. Most often topical medication means application to body surfaces such as the skin or mucous membranes to treat ailments via a large range of classes ...
applications. This is produced on a commercial scale and marketed as tea tree oil. ''Melaleuca cajuputi'' is used to produce a similar oil, known as cajuput oil, which is used in
Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainland ...
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 ''Callistemon'' is a genus of shrubs in the family Myrtaceae, first described as a genus in 1814. The entire genus is endemic to Australia but widely cultivated in many other regions and naturalised in scattered locations. Their status as ...
'') 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 The Royal Botanic Garden Edinburgh (RBGE) is a scientific centre for the study of plants, their diversity and conservation, as well as a popular tourist attraction. Founded in 1670 as a physic garden to grow medicinal plants, today it occupies ...
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 Arthur Maybee Chanter was an Australian composer, conductor, music teacher, choir master and musician. An accomplished pianist and watercolorist, Chanter was among the earliest music graduates of the University of Melbourne, where he was instruct ...
(1866-1950)


See also

* List of ''Melaleuca'' species


References


Further reading

* * * * *


External links

* {{Taxonbar, from=Q606617 Myrtaceae genera Myrtales of Australia Rosids of Western Australia