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{{Otheruses4|the plant genus|the [[novel]] by [[Murray Bail]]|Eucalyptus (novel)}}
{{Taxobox
| color = lightgreen
| name = ''Eucalyptus''
| image = Eucalyptus flowers2.jpg
| image_width = 250px
| image_caption = ''Eucalyptus melliodora'' foliage and flowers
| regnum = [[Plant]]ae
| divisio = [[Flowering plant|Magnoliophyta]]
| classis = [[Magnoliopsida]]
| ordo = [[Myrtales]]
| familia = [[Myrtaceae]]
| genus = '''''Eucalyptus'''''
| genus_authority = [[Charles Louis L'Héritier de Brutelle|L'Hér.]]
| range_map = Distribution.eucalyptus.png
| range_map_width = 250px
| range_map_caption = natural range
| subdivision_ranks = Species
| subdivision =
About 700; see the [[List of Eucalyptus species]]
}}
'''''Eucalyptus''''' (From Greek, ευκάλυπτος = "Well covered") is a diverse [[genus]] of [[tree]]s (and a few shrubs), the members of which dominate the tree flora of [[Australia]]. There are more than seven hundred species of ''Eucalyptus'', mostly native to Australia, with a very small number found in adjacent parts of [[New Guinea]] and [[Indonesia]] and one as far north as the [[Philippine islands]].
Members of the genus can be found in almost every region of the Australian continent, because they have adapted to all of its climatic conditions; in fact no other continent is so characterised by a single genus of tree as Australia is by its eucalyptus. Many, but far from all, are known as '''gum trees''' in reference to the habit of many species to exude copious sap from any break in the bark (e.g. [[Scribbly Gum]]).
==Description==
[[Image:Tasmania logging 08 Mighty tree.jpg|left|thumb|180px|''[[Eucalyptus regnans]]'', a forest tree, showing crown dimension, [[Tasmania]], [[Australia]]]]
[[Image:TocumwalTownBeach.jpg|right|thumb|180px|''[[Eucalyptus camaldulensis]]'', immature, woodland trees, showing collective crown habit, Murray River, [[Tocumwal]], [[New South Wales]], [[Australia]]]]
[[Image:Eucalyptus cretata.jpg|right|thumb|180px|''[[Eucalyptus cretata]]'', juvenile, showing low branching ‘mallee’ form, [[Melbourne]], [[Victoria, Australia]] ]]
[[Image:Eucalyptus angustissima1.jpg|thumb|left|180px|''[[Eucalyptus angustissima]]'', showing shrub form, [[Melbourne]], [[Victoria, Australia]]]]
[[Image:Eucalyptus platypus.jpg|thumb|right|180px|''[[Eucalyptus platypus]]'', showing ‘Marlock’ form, [[Melbourne]]]]
=== Size and habit ===
A ''Eucalyptus'' may be mature as a low shrub or as a very large tree. There are three main habit and four size categories that [[species]] can be divided into.
As a generalisation "[[forest]] trees" are single-stemmed and have a [[crown (botany)|crown]] forming a minor proportion of the whole tree height. "[[Woodland]] trees" are single-stemmed although they may branch at a short distance above ground level.
"[[Mallee (habit)|Mallees]]" are multi-stemmed from ground level, usually less than 10 metres in height, often with the crown predominantly at the ends of the branchlets and individual plants may combine to form either an open or closed formation. Many mallee trees may be so low growing as to be considered a [[shrub]].
Apart from the forest tree, woodland tree, mallee and shrub habits two further tree forms are notable in [[Western Australia]]. One of these is the "[[mallet (habit)|mallet]]", which is a small to medium-sized tree, usually of steep branching habit, sometimes fluted at the base of the trunk and often with a conspicuously dense, [[terminal]] crown. It is the habit usually of mature healthy specimens of ''Eucalyptus occidentalis'', ''E. astringens'', ''E. spathulata'', ''E. gardneri'', ''E. dielsii'', ''E. forrestiana'', ''E. salubris'', ''E. clivicola'' and ''E. ornata''. The smooth [[bark]] of mallets often has a satiny sheen and may be white, cream, grey, green or copper.
Another habit category used in Western Australia is the "[[marlock]]". This has been variously applied but Brooker & Hopper (2001) defined the term and restricted the use to describe the more or less pure stands of short, erect, thin-stemmed "trees" that do not produce [[lignotuber]]s. These are easily seen and recognised in stands of ''E. platypus'', ''E. vesiculosa'' and the unrealted ''E. stoatei''. The marlock is distinguished from mallets which are taller and have a characteristic steep branching habit. The origin and use of the term "morrel" is somewhat obscure and appears to apply to trees of the western Australian wheatbelt and [[goldfields]] which have a long, straight trunk, completely rough barked. It is now used mainly for ''E. longicornis'' (Red Morell) and ''E. melanoxylon'' (Black Morrel).
Tree sizes follow the [[Convention (norm)|convention]] of:
:*Small - to 10 metres in height
:*Medium sized - 10 to 30 metres in height
:*Tall - 30 to 60 metres in height
:*Very Tall - over 60 metres in height
=== Leaves ===
Nearly all ''Eucalyptus'' are [[evergreen]] but some tropical species lose their leaves at the end of the dry season. As in other members of the [[Myrtaceae|Myrtle]] family, ''Eucalyptus'' leaves are covered with oil glands. The copious oils produced are an important feature of the genus.
[[Image:Eucalyptus tetragona - glaucous leaves close.jpg|right|thumb|180px|''[[Eucalyptus tetragona]]'', showing glaucous leaves & stems]]
The leaves on a mature ''Eucalyptus'' plant are commonly [[lanceolate]], [[Leaf#Characteristics of the petiole|petiolate]], apparently [[Leaf#Arrangement on the stem|alternate]] and waxy or glossy green. In contrast the leaves of seedlings are frequently [[Leaf#Arrangement on the stem|opposite]], [[Leaf#Characteristics of the petiole|sessile]] and [[Leaf#Surface of the leaf|glaucous]]. However there are numerous exceptions to this pattern. Many species such as ''[[Eucalyptus melanophloia|E. melanophloia]]'' and ''E. setosa'' retain the juvenile leaf form even when the plant is reproductively mature. Some species such as ''[[Eucalyptus macrocarpa|E. macrocarpa]]'', ''[[Eucalyptus rhodantha|E. rhodantha]]'' and ''[[Eucalyptus. crucis|E. crucis]]'' are sought after ornamentals due to this lifelong juvenile leaf form. A few species such as ''[[Eucalyptus petraea|E. petraea]]'', ''[[Eucalyptus dundasii|E. dundasii]]'' and ''[[E. lansdowneana]]'' have shiny green leaves throughout their life cycle. ''[[Eucalyptus caesia|E. caesia]]'' exhibits the opposite pattern of leaf development to most ''Eucalyptus'', with shiny green leaves in the seedling stage and dull, glaucous leaves in mature crowns. The contrast between juvenile and adult leaf phases is valuable in field identification.
Four leaf phases are recognised in the development of a ''Eucalyptus'' plant - the ‘seedling’, ‘juvenile’, ‘intermediate’ and ‘adult’ phases. However there is no definite transitional point between the phases. The intermediate phase, when the largest leaves are often formed, links the juvenile and adult phases.<ref name=FieldGuide>Brooker & Kleinig (2001)</ref> Most species do not flower until adult foliage starts to appear; ''E. cinerea'' and ''E. perriniana'' are notable exceptions.
In all except a few species the leaves form in pairs on opposite sides of a square stem, consecutive pairs being at right angles to each other (decussate). In some narrow-leaved species - for example ''[[Eucalyptus oleosa|E. oleosa]]'' - the seedling leaves after the second leaf pair are often clustered in a detectable spiral arrangement about a five sided stem. After the spiral phase, which may last from several to many nodes, the arrangement reverts to decussate by the absorption of some of the leaf bearing faces of the stem. In those species with opposite adult foliage the leaf pairs, which have been formed opposite at the stem apex, become separated at their bases by unequal elongation of the stem to produce the apparently alternate adult leaves.
[[Image:Eucalyptus leucoxylon1.jpg|left|thumb|''[[Eucalyptus leucoxylon]]'' var. '''‘Rosea’''' showing flowers & buds with operculum present]]
[[Image:E.sideroxylon, branchlets, stems, leaves, capsules & buds.jpg|right|thumb|''Eucalyptus sideroxylon'', showing fruit (capsules) & buds with operculum present.]]
=== Flowers ===
The most readily recognisable characteristics of Eucalyptus species are its distinctive flowers and fruit (capsule). Flowers have numerous fluffy stamens which may be white, cream, yellow, pink or red; in bud the stamens are enclosed in a cap known as an operculum which is composed of the fused sepals or petals or both. Thus flowers have no petals, decorating themselves instead with the many showy stamens. As the stamens expand the operculum is forced off, splitting away from the cup-like base of the flower; this is one of the features that that unites the genus. The name Eucalyptus, from the Greek words ''eu-'', well, and ''kaluptos'', cover, meaning "well-covered", describes the operculum. The woody fruits or capsules, known as gumnuts, are roughly cone-shaped and have valves at the end which open to release the seeds. Most species do not flower until adult foliage starts to appear; ''[[Eucalyptus cinerea]]'' and ''[[Eucalyptus perriniana]]'' are notable exceptions.
[[Image:Eucalyptus tree.jpg|thumb|200px|left|''Eucalyptus sp'' in [[East Gippsland]], [[Victoria, Australia]], showing ‘ribbon’ bark form.]]
[[Image:Eucalyptus sideroxylon - bark.jpg|left|thumb|200px|The dark, fissured ‘Ironbark’ bark of ''[[Eucalyptus sideroxylon]]'']]
=== Bark ===
The appearance of ''Eucalyptus'' bark will vary with the age of the plant, the manner of bark shed, the length of the bark fibres, the degree of furrowing, the thickness, the hardness and the colour. All mature eucalypts put on an annual layer of bark, which contributes to the increasing diameter of the stems. In some species the outermost layer dies and is annually deciduous either in long strips (as in ''[[Eucalyptus sheathiana]]'') or in variably sized flakes (''[[Eucalyptus diversicolor]]'', ''[[Eucalyptus cosmophylla]]'' or ''[[Eucalyptus cladocalyx]]''). These are the gums or smooth-barked species. The gum bark may be dull, shiny or satiny (as in ''[[Eucalyptus ornata]]'') or matt (''[[Eucalyptus cosmophylla]]''). In many species the dead bark is retained. Its outermost layer gradually fragments with weathering and sheds without altering the essentially rough barked nature of the trunks or stems - for example ''[[Eucalyptus marginata]]'', ''[[Eucalyptus jacksonii]]'', ''[[Eucalyptus obliqua]]'' and ''[[Eucalyptus porosa]]''.
[[Image:Eucalyptus deglupta-trees.jpg|thumb|right|200px|The extraordinary coloured bark of ''[[Eucalyptus deglupta]]'' native to South East Asia]]
Many species are ‘half-barks’ or ‘blackbutts’ in which the dead bark is retained in the lower half of the trunks or stems - for example, ''[[Eucalyptus brachycalyx]]'', ''[[Eucalyptus ochrophloia]]'' and ''[[Eucalyptus occidentalis]]'' - or only in a thick, black accumulation at the base, as in ''[[Eucalyptus clelandii]]''. Some species in this category - for example - ''[[Eucalyptus youngiana]]'' - the rough basal bark is very ribbony at the top, where it gives way to the smooth upper stems. The smooth upper bark of the half barks and that of the completely smooth-barked trees and mallees can produce remarkable colour and interest, for example ''[[Eucalyptus deglupta]]''.<ref name=FieldGuide/>
[[Image:Eucalyptus bark.jpg|right|thumb|200px|The '''box''' bark of ''[[Eucalyptus quadrangulata]]'', or '''White Box''']]
====Bark characteristics====
* '''Stringybark''' - consists of long-fibres and can be pulled off in long pieces. It is usually thick with a spongy texture.
* '''Ironbark''' - is hard, rough and deeply furrowed. It is impregnated with dried kino (a [[Sap (plant)|sap]] exuded by the tree) which gives a dark red or even black colour.
* '''Tessellated''' - bark is broken up into many distinct flakes. They are [[cork (material)|corkish]] and can flake off.
* '''Box''' - has short fibres. Some also show tessellation.
* '''Ribbon''' - this has the bark coming off in long thin pieces but still loosely attached in some places. They can be long ribbons, firmer strips or twisted curls.
==Species and hybridism==
There are over 700 [[species]] of Eucalyptus; refer to the '''[[List of Eucalyptus species]]''' for a comprehensive list of species. It is believed that all eucalypts are related either closely or remotely. Some have [[divergent evolution|diverged]] from the mainstream of the [[genus]] to the extent that they are quite isolated [[genetics|genetically]] and are able to be recognised by only a few relatively [[invariant]] [[characteristics]]. Most, however, may be regarded as belonging to large or small groups of related species, which are often in [[geographical]] contact with each other and between which [[gene]] exchange still occurs. In these situations many species will appear to grade into one another and intermediate forms are common. In other words, some species are relatively fixed genetically, as expressed in their [[morphology (biology)|morphology]], while others have not diverged completely from their nearest relatives.
Hybrid individuals have not always been recognised as such on first collection and some have been named as new species, such as ''E. chrysanth''a (''E. preissiana'' × ''E. sepulcralis'') and ''E.'' "rivalis" (''E. marginata'' × ''E. megacarpa''). Hybrid combinations are not particularly common in the field, but some other published species have been suggested to be hybrid combinations and are frequently seen in Australia. For example, ''E. erythrandra'' is believed to be ''E. angulosa'' × ''E. teraptera'' and due to its wide distribution is often referred to in texts.<ref name=FieldGuide/>
==Related genera==
A small genus of similar trees, ''[[Angophora]]'', has also been known since the [[18th century]]. In [[1995]] new evidence, largely genetic, indicated that some prominent ''Eucalyptus'' species were actually more closely related to ''Angophora'' than to the other eucalypts; they were split off into the new [[genus]] ''[[Corymbia]]''. Although separate, the three groups are allied and it remains acceptable to refer to the members of all three genera ''Angophora'', ''Corymbia'' and ''Eucalyptus'' as "eucalypts". The coolibah trees, referred to in [[Waltzing Matilda]], are ''Eucalyptus'' ''[[Eucalyptus coolabah|E. coolabah]]'' and ''[[Eucalyptus microtheca|E. microtheca]]''.
[[Image:Tasmania logging 16 Styx a tree in danger.jpg|thumb|right|200px|''Eucalyptus regnans'' exceeding 80 metres, in an area of extensive logging, Tasmania]]
==Tall timber==
Today, specimens of the Australian Mountain Ash, ''[[Eucalyptus regnans]]'', are among the tallest trees in the world at up to 92 metres in height <ref>{{cite web | url=http://www.forestrytas.com.au/forestrytas/tasfor/tasforests_12/tasfor_12_09.pdf | media=PDF | title=Tasmania's Tallest Trees | author=J.E. Hickey, P. Kostoglou, G.J. Sargison | publisher=Forestry Tasmania | accessdate=2005-01-27}}</ref> and the tallest of all flowering plants ([[Angiosperms]]); taller trees such as the [[Coast Redwood]] are all [[conifer]]s ([[Gymnosperms]]). There is credible evidence however that at the time of European settlement of Australia some Mountain Ash were indeed the tallest plants in the world.
==Tolerance==
Most eucalypts are not tolerant of frost, or only tolerate light frosts down to -3°C to -5°C; the hardiest, are the so-called Snow Gums such as ''[[Eucalyptus pauciflora]]'' which is capable of withstanding cold and frost down to about -20°C. Two sub-species, ''E. pauciflora subsp. niphophila'' and ''E. pauciflora subsp. debeuzevillei'' in particular are even hardier and can tolerate even quite severe [[winter]]s. Several other species, especially from the high plateau and mountains of central [[Tasmania]] such as ''[[Eucalyptus coccifera]]'', ''[[Eucalyptus subcrenulata]]'', and ''[[Eucalyptus gunnii]]'', have produced extreme cold hardy forms and it is seed procured from these [[genetics|genetically]] hardy strains that are planted for ornament in colder parts of the world.
==Animal relationships==
[[Image:Koala-ag1.jpg|thumb|left|220px|''Phascolarctos cinereus'' [[Koala]] eating ''eucalyptus'' leaves]]
An [[essential oil]] extracted from eucalyptus leaves contains compounds that are powerful natural disinfectants and which can be toxic in large quantities. Several [[marsupial herbivore]]s, notably [[koala]]s and some [[possum]]s, are relatively tolerant of it. The close correlation of these oils with other more potent toxins called formylated [[phloroglucinol]] compounds allows koalas and other [[marsupial]] species to make food choices based on the smell of the leaves. However, it is the formylated phloroglucinol compounds that are the most important factor in choice of leaves by koalas. Eucalyptus flowers produce a great abundance of [[nectar]], providing food for many [[pollinator]]s including [[insect]]s, birds, [[Chiroptera|bat]]s and [[possum]]s. Despite the fact that eucalyptus trees are well-defended from herbivores by their toxic essential oils they do have their share of insect pests, such as the Eucalyptus [[Longhorn Beetle|Longhorn Borer]] [[Beetle]], ''[[Phoracantha semipunctuata]]'', or the aphid-like [[psyllid]]s known as "[[Bell Miner|bell lerps]]," both of which have become established as pests throughout the world wherever eucalypts are cultivated.
{{See|list of Lepidoptera which feed on Eucalyptus}}
==Hazards==
[[Image:Log embedded in white box.jpg|thumb|200px|right|A fallen log is embedded in a ''[[Eucalyptus albens]]''. This formation is the [[CODIT|tree's response]].]]
Some species of Eucalyptus have a habit of dropping entire branches off as they grow. Eucalyptus forests are littered with dead branches. The Australian Ghost Gum ''[[Eucalyptus papuana]]'' is also termed the "widow maker," due to the high number of pioneer tree-felling workers who were killed by falling branches. Many people have been killed as they camped underneath the trees. It is thought the trees shed very large branches to conserve water during periods of drought. This may be the real reason behind the [[drop bear]] story told to children - the idea is to keep them away from being under dangerous branches.
==Fire==
On warm days vapourised eucalyptus oil rises above the [[The Bush|bush]] to create the characteristic distant blue haze of the Australian landscape. Eucalyptus oil is highly flammable (trees have been known to explode<ref>{{Cite web |url=http://library.csustan.edu/bsantos/section3.htm |title=Section Three: Problems, Cares, Economics, and Species |work=The Eucalyptus of California |first=Robert L. |last=Santos |publisher=California State University |year=1997}}</ref><ref>{{Cite web |url=http://www.robertsward.com/eucmore.htm |title=Eucalytus Roulette (con't) |publisher=Robert Sward: Poet, Novelist and Workshop Leader }}</ref>) and [[bush fire]]s can travel easily through the oil-rich air of the tree crowns. The dead bark and fallen branches are also flammable. Eucalypts are well adapted for periodic fires, in fact most species are dependent on them for spread and [[regeneration (biology)|regeneration]]. {{Fact|date=June 2007}} They do this via [[lignotuber]]s, epicormic buds under the bark and from fire-germinated seeds sprouting in the ashes. {{Fact|date=June 2007}}
[[Image:Eucalyptus forest2.jpg|thumb|280px|left|Eucalyptus forest in a state of regeneration]]
Eucalypts originated between 35 and 50 million years ago, not long after [[Australia-New Guinea]] separated from [[Gondwana]], their rise coinciding with an increase in fossil charcoal deposits (suggesting that fire was a factor even then), but they remained a minor component of the Tertiary rainforest until about 20 million years ago when the gradual drying of the continent and depletion of soil nutrients led to the development of a more open forest type, predominantly ''[[Casuarina]]'' and ''[[Acacia]]'' species. With the arrival of the first humans about 50 thousand years ago fires became much more frequent and the fire-loving eucalypts soon came to account for roughly 70% of Australian forest.
Eucalypts regenerate quickly after [[fire]]. After the [[Canberra bushfires of 2003]], hectares of imported species were killed, but in a matter of weeks the gum trees were putting out suckers and looking generally healthy. {{Fact|date=June 2007}}
The two valuable timber trees, Alpine Ash ''[[Eucalyptus delegatensis|E. delegatensis]]'' and Mountain Ash ''[[Eucalyptus regnans|E. regnans]]'', are killed by fire and only regenerate from seed. The same 2003 bushfire that had little impact on forests around [[Canberra]] resulted in thousands of hectares of dead ash forests. However, a small amount of ash survived and put out new suckers as well. There has been some debate as to whether to leave the stands, or attempt to harvest the mostly undamaged timber, which is increasingly recognised as a damaging practice.
==Cultivation and uses==
[[Image:NamadgiTree.jpg|thumb|''[[Eucalyptus niphophila]]'' in [[Namadgi National Park]]]]
Eucalyptus have many uses which have made them [[economically]] important trees. Perhaps the [[Karri]] and the [[Eucalyptus melliodora|Yellow box]] varieties are the best known. Due to their fast growth the foremost benefit of these trees is the wood. They provide many desirable characteristics for use as ornament, timber, firewood and [[pulpwood]]. Fast growth also makes eucalypts suitable as [[windbreak]]s. Eucalypts draw a tremendous amount of water from the soil through the process of [[transpiration]]. They have been planted (or re-planted) in some places to lower the water table and reduce [[soil salination]]. Eucalypts have also been used as a way of reducing [[malaria]] by draining the soil in Algeria, Sicily<ref>{{cite web | url=http://www.botanical.com/botanical/mgmh/e/eucaly14.html | title=A Modern Herbal:Eucalyptus | author=Mrs. M. Grieve | accessdate=2005-01-27}}</ref> and also in Europe and California<ref>{{cite web | author=Santos, Robert L | url=http://wwwlibrary.csustan.edu/bsantos/section2.htm#FIGHTING | title=Section Two: Physical Properties and Uses |work=The Eucalyptus of California | publisher=California State University |year=1997}}</ref>. Drainage removes swamps which provide a habitat for [[mosquito]] [[larva]]e, but such drainage can also destroy ecologically productive areas.
[[Eucalyptus oil]] is readily [[steam distillation|steam distilled]] from the leaves and can be used for cleaning, deodorising, and in very small quantities in [[food]] supplements; especially [[sweets]], cough drops and decongestants. Eucalyptus oil has insect repellent properties (Jahn 1991 a, b; 1992), and is an active ingredient in some commercial mosquito repellents (Fradin & Day 2002).
The [[nectar (plant)|nectar]] of some eucalyptus produces high quality [[monofloral honey]]. The ghost gum's leaves were used by [[Indigenous Australians|Aborigines]] to catch fish. Soaking the leaves in water releases a mild tranquilliser which stuns fish temporarily. Eucalyptus is also used to make the [[digeridoo]], a musical wind instrument made popular by the Aborigines of Australia.
All parts of the eucalyptus may be used to make plant [[dyes]] that are substantive on protein fibres ([[silk]] and [[wool]]) simply by processing the plant part with [[water]]{{Fact|date=August 2007}}. Colours to be achieved range from yellow and orange through green, tan, chocolate and deep rust red. The material remaining after processing can be safely used as mulch{{Fact|date=August 2007}}.
== History ==
[[Image:Sir Joseph Banks, president of the Royal Society.jpg|left|thumb|Sir Joseph Banks]]Although Eucalypts must have been seen by the very early European explorers and collectors, no botanical collections of them are known to have been made until [[1770]] when [[Joseph Banks]] and [[Daniel Solander]] arrived at [[Botany Bay]] with [[Captain James Cook]]. There they collected specimens of ''E. gummifera'' and later, near the [[Endeavour River]] in northern ''Queensland'', they collected ''E. platyphylla''; neither of these species was named as such at the time.
In [[1777]], on Cook's third expedition, David Nelson collected a eucalypt on [[Bruny Island]] in southern [[Tasmania]]. This specimen was taken to the [[British Museum]] in [[London]], and it was named ''Eucalyptus obliqua'' by the French botanist [[L'Héritier]], who was working in London at the time. He coined the generic name from the Greek roots ''eu'' and ''calyptos'', meaning "well" and "covered" in reference to the [[operculum (botany)|operculum]] of the flower bud. This organ protects the developing flower parts as the flower develops and is shed by the pressure of the emerging [[stamens]] at flowering.
The name ''obliqua'' was derived from the Latin ''obliquus'', meaning "oblique" which is the [[botany|botanical]] term describing a [[leaf]] base where the two sides of the leaf blade are of unequal length and do not meet the petiole at the same place.
In naming ''E. obliqua'', [[Charles Louis L'Héritier de Brutelle|L'Héritier]] caused to be perpetuated, most likely by accident, a feature common to all eucalypts - the operculum. In his choice of a specific name, he recognised not only the characteristic feature of ''E. obliqua'', but one common to many other species as well. ''E. obliqua'' was published in [[1788]]-89 and coincides with the date of the first official European settlement of Australia.
[[Image:Von mueller.jpg|right|thumb|Ferdinand von Mueller]]
Between 1788-89 and the turn of the nineteenth century several more species of ''Eucalyptus'' were named and published. Most of these were by the English botanist [[James Edward Smith]] and most were, as might be expected, trees of the [[Sydney]] region. These include the economically valuable ''E. pilularis'', ''E. saligna'' and ''E. tereticornis''.
The nineteenth century saw the endeavours of several of the great botanists in Australian history, particularly [[Ferdinand von Mueller]], whose work on eucalypts contributed greatly to the first comprehensive account of the genus in [[George Bentham]]'s ''Flora Australiensis'' in 1867 - which today remains the only complete Australian flora. The account in Bentham is the most important early systematic treatment of the genus. Bentham divided the genus into five series whose distinctions were based on characteristics of the stamens, particularly the anthers (Mueller, 1879-84), elborated further by Joseph Henry Maiden (1903-33), and taken even further by William Faris Blakely (1934). By this time the anther system had become too complex to be workable and more recent systematic work has concentrated on the characteristics of buds, fruits, leaves and bark.
The first endemic Western Australian ''Eucalyptus'' to be collected and subsequently named was the yate (''E. cornuta'') by the French botanist [[La Billardiére]], who collected in what is now the [[Esperance]] area in [[1792]].<ref name=FieldGuide/>
==Plantation and ecological problems==
''Eucalyptus'' was first introduced to the rest of the world by [[Joseph Banks|Sir Joseph Banks]], [[botanist]], on the [[James Cook|Cook]] expedition in 1770. They have subsequently been introduced to many parts of the world, notably [[California]], [[Brazil]], [[Ecuador]], [[Colombia]], [[Ethiopia]], [[Morocco]], [[Portugal]], [[South Africa]], [[Israel]], [[Galicia (Spain)|Galicia]] and [[Chile]]. In [[Spain]] they have been planted in pulpwood [[plantation]]s, replacing native [[oak]] woodland. ''Eucalyptus'' are the basis for several industries, such as sawmilling, pulp, charcoal and others. Several species have become [[invasive species|invasive]] and are causing major problems for local ecosystems.
===California===
In the 1850s many Australians traveled to [[California]] to take part in the [[California Gold Rush]]. Much of California has a similar climate to parts of Australia and some people got the idea of introducing eucalypts. By the early 1900s thousands of acres of eucalypts were planted with the encouragement of the state government. It was hoped that they would provide a renewable source of timber for construction and furniture making. However, this did not happen, partly because the trees were cut when they were too young and partly because the Americans did not know how to process the cut trees to prevent the wood from twisting and splitting.<ref>{{Cite web |url=http://www.library.csustan.edu/bsantos/euctoc.htm |work=The Eucalyptus of California |first=Robert L. |last=Santos |publisher=California State University |work=The Eucalyptus of California |title=Seeds of Good or Seeds of Evil? |year=1997}}</ref>
One way in which the eucalyptus, mainly the blue gum ''E. globulus'', proved valuable in California was in providing windbreaks for highways, orange groves, and other farms in the mostly treeless central part of the state. They are also admired as shade and ornamental trees in many cities and gardens.
''Eucalyptus'' forests in California have been criticized because they compete with native plants and do not support native animals. Fire is also a problem. The 1991 [[Oakland Hills firestorm]] which destroyed almost 3,000 homes and killed 25 people was partly fueled by large numbers of eucalypts in the area close to the houses.<ref>{{Cite web |last=Williams |first=Ted |title=America's Largest Weed |publisher=Audubon Magazine |month=January |year=2002 |url=http://magazine.audubon.org/incite/incite0201.html}}</ref>
In some parts of California eucalypt forests are being removed and native trees and plants restored. Individuals have also illegally destroyed some trees and are suspected of introducing insect pests from Australia which attack the trees.<ref>{{Cite web |title=Tree Wars: The Secret Life of Eucalyptus |first=Heather |last=Henter |month=January |year=2005 |publisher=University of California, San Diego |work=Alumni |url=http://alumni.ucsd.edu/magazine/vol2no1/features/wars.htm}}</ref>
===Brazil===
In 1910 ''Eucalyptus'' was introduced to Brazil for [[timber]] substitution and the [[charcoal|vegetal coal]] industry. It has adpated very well to the local environmental conditions{{Fact|date=August 2007}} and today there are around 5 million hectares planted. The wood produced by the tree is highly appreciated by the charcoal and pulp and paper industries. The short rotation allows a larger wood production and supply wood for several other activities, helping to preserve the native forests from logging. When well managed the plantations are sustainable and the soil can sustain endless replantations. Eucalyptus plantations are also used as [[windbreak|wind breaks]].
===Ethiopia===
This species was introduced to [[Ethiopia]] in either 1894 or 1895, either by Emperor [[Menelik II of Ethiopia|Menelik II]]'s French advisor Mondon-Vidailhet or the Englishman Captain O'Brian. Due to massive deforestation around his new capital city [[Addis Ababa]] caused by a growing appetite for [[fire wood]], Emperor [[Menelik II of Ethiopia|Menelik II]] endorsed its planting around that city; according to [[Richard R.K. Pankhurst]], "The great advantage of the eucalypts was that they were fast growing, required little attention and when cut down grew up again from the roots; it could be harvested every ten years. The tree proved successful from the onset".<ref>Pankhurst p. 246</ref> Plantations of eucalypts spread from the capital to other growing urban centers such as [[Debre Marqos]]; Pankhurst reports that the most common species found in Addis Ababa in the mid-1960s was ''[[Eucalyptus globulus|E. globulus]]'', although he also found ''[[Eucalyptus melliodora|E. melliodora]]'' and ''[[Eucalyptus rostrata|E. rostrata ]]'' in significant numbers. David Buxton, writing of central Ethiopia in the mid-1940s, observed that eucalyptus trees "have become an integral -- and a pleasing -- element in the [[Shewa|Shoan]] landscape and has largely displaced the slow-growing native 'cedar' or juniper."<ref>David Buxton, ''Travels in Ethiopia'', second edition (London: Benn, 1957), p. 48</ref>
Popular opposition soon developed that in 1913 a proclamation was issued ordering a partial destruction of all standing trees, and their replacement with [[mulberry]] trees. "The proclamation," Pankhurst notes, "however remained a dead letter; there is no evidence of eucalypts being uprooted, still less of mulberry trees being planted."<ref>Pankhurst p. 247</ref> The eucalypt remains a defining feature of Addis Ababa.
==Photo gallery==
<gallery>
<!-- Please only add pictures where the species or variety of tree has been identified and the location - there are many varieties of eucalyptus and it is not encyclopaedic to say merely "eucalyptus"-->
Image:Eucalyptus forest.jpg|Eucalyptus forest in [[East Gippsland Shire|East Gippsland]], [[Victoria (Australia)|Victoria]]. Mostly ''Eucalyptus albens'' (white box).
Image:Eucalyptus forest3.jpg|Eucalyptus forest in [[East Gippsland Shire|East Gippsland]], [[Victoria (Australia)|Victoria]]. Mostly ''Eucalyptus albens'' (white box).
Image:Eucalypt forest.jpg|Eucalyptus forest in [[East Gippsland Shire|East Gippsland]], [[Victoria (Australia)|Victoria]]. Mostly ''Eucalyptus albens'' (white box).
Image:Eucalyptustreewithsun.JPG|A eucalyptus tree with the sun shining through its branches.
Image:Applebox.JPG|''Eucalyptus bridgesiana'' (Apple box) on [[Red Hill, Australian Capital Territory]].
image:euc.uk.600pix.jpg|''Eucalyptus gunnii'' planted in southern [[England]]. The lower part of the trunk is covered in [[ivy]].
Image:Eucalyptus cinera x pulverulenta.jpg|''Eucalyptus cinerea'' x ''pulverulenta'' - National Botanical Gardens Canberra
Image:Eucalyptus gall.jpg|Eucalyptus Pink Waxy Scale Insects
Image:CPonte Eucalyptus.jpg|''Eucalyptus grandis''. Province of Buenos Aires, Argentina.
Image:Eucalipto Galicia.JPG|Eucalyptus plantation in [[Galicia (Spain)|Galicia]] in Northwest [[Spain]]
Image:Eucalyptus rubida.jpg| ''Eucalyptus rubida'' ([[Candlebark gum]]) in [[Burra, New South Wales]].
Image:2007 0731klklk0151.JPG|This tree in [[Heathcote National Park]] has a serious problem.
</gallery>
==Notes==
{{Reflist|2}}
==References==
* {{Cite book |last=Brooker |first=M.I.H. |coauthors=Kleinig, D.A. |title=Field Guide to Eucalyptus |publisher=Bloomings |location=Melbourne |year=2001}}
*{{Cite book |first=Richard |last=Pankhurst |title=Economic History of Ethiopia |location=Addis Ababa |publisher=Haile Selassie I University |year=1968}}
==External links==
{{sisterlinks}}
* [http://www.anbg.gov.au/cpbr/cd-keys/Euclid/sample/html/index.htm EUCLID Sample], CSIRO
* [http://farrer.riv.csu.edu.au/ASGAP/eucalypt.html The Eucalyptus Page]
* [http://plantnet.rbgsyd.nsw.gov.au/PlantNet/Euc/ EucaLink]
* [http://www.dn.com.au Currency Creek Arboretum - Eucalypt Research]
*[http://www.cirrusimage.com/tree_Eucalyptus.htm ''Eucalyptus globulus''] Diagnostic photos: tree, leaves, bark
*[http://www.hort.purdue.edu/newcrop/duke_energy/Eucalyptus.html Handbook of Energy Crops] Duke, James A. 1983.
*[http://www.library.csustan.edu/bsantos/euctoc.htm The Eucalyptus of Califonia: Seeds of Good or Seeds of Evil?] Santos, Robert. 1997 Denair, CA : Alley-Cass Publications
*[http://www.geocities.com/RainForest/7813/euca_1.htm Impacts of Monoculture: The Case of Eucalyptus Plantations in Thailand] a paper for the Monocultures: Environmental and Social Effects and Sustainable Alternatives Conference, June 2-6 1996, Songkhla, Thailand, prepared by Areerat Kittisiri, Rural Reconstruction and Friends Association (RRAFA), Bangkok, Thailand
===Medicinal resources, eucalyptus essential oil===
* http://www.botanical.com/botanical/mgmh/e/eucaly14.html
* http://www.henriettesherbal.com/eclectic/bpc1911/eucalyptus_oleu.html
[[Category:Myrtales of Australia]]
[[Category:Medicinal plants]]
[[Category:Eucalyptus| Eucalyptus]]
{{Taxobox
| color = lightgreen
| name = ''Eucalyptus''
| image = Eucalyptus flowers2.jpg
| image_width = 250px
| image_caption = ''Eucalyptus melliodora'' foliage and flowers
| regnum = [[Plant]]ae
| divisio = [[Flowering plant|Magnoliophyta]]
| classis = [[Magnoliopsida]]
| ordo = [[Myrtales]]
| familia = [[Myrtaceae]]
| genus = '''''Eucalyptus'''''
| genus_authority = [[Charles Louis L'Héritier de Brutelle|L'Hér.]]
| range_map = Distribution.eucalyptus.png
| range_map_width = 250px
| range_map_caption = natural range
| subdivision_ranks = Species
| subdivision =
About 700; see the [[List of Eucalyptus species]]
}}
'''''Eucalyptus''''' (From Greek, ευκάλυπτος = "Well covered") is a diverse [[genus]] of [[tree]]s (and a few shrubs), the members of which dominate the tree flora of [[Australia]]. There are more than seven hundred species of ''Eucalyptus'', mostly native to Australia, with a very small number found in adjacent parts of [[New Guinea]] and [[Indonesia]] and one as far north as the [[Philippine islands]].
Members of the genus can be found in almost every region of the Australian continent, because they have adapted to all of its climatic conditions; in fact no other continent is so characterised by a single genus of tree as Australia is by its eucalyptus. Many, but far from all, are known as '''gum trees''' in reference to the habit of many species to exude copious sap from any break in the bark (e.g. [[Scribbly Gum]]).
==Description==
[[Image:Tasmania logging 08 Mighty tree.jpg|left|thumb|180px|''[[Eucalyptus regnans]]'', a forest tree, showing crown dimension, [[Tasmania]], [[Australia]]]]
[[Image:TocumwalTownBeach.jpg|right|thumb|180px|''[[Eucalyptus camaldulensis]]'', immature, woodland trees, showing collective crown habit, Murray River, [[Tocumwal]], [[New South Wales]], [[Australia]]]]
[[Image:Eucalyptus cretata.jpg|right|thumb|180px|''[[Eucalyptus cretata]]'', juvenile, showing low branching ‘mallee’ form, [[Melbourne]], [[Victoria, Australia]] ]]
[[Image:Eucalyptus angustissima1.jpg|thumb|left|180px|''[[Eucalyptus angustissima]]'', showing shrub form, [[Melbourne]], [[Victoria, Australia]]]]
[[Image:Eucalyptus platypus.jpg|thumb|right|180px|''[[Eucalyptus platypus]]'', showing ‘Marlock’ form, [[Melbourne]]]]
=== Size and habit ===
A ''Eucalyptus'' may be mature as a low shrub or as a very large tree. There are three main habit and four size categories that [[species]] can be divided into.
As a generalisation "[[forest]] trees" are single-stemmed and have a [[crown (botany)|crown]] forming a minor proportion of the whole tree height. "[[Woodland]] trees" are single-stemmed although they may branch at a short distance above ground level.
"[[Mallee (habit)|Mallees]]" are multi-stemmed from ground level, usually less than 10 metres in height, often with the crown predominantly at the ends of the branchlets and individual plants may combine to form either an open or closed formation. Many mallee trees may be so low growing as to be considered a [[shrub]].
Apart from the forest tree, woodland tree, mallee and shrub habits two further tree forms are notable in [[Western Australia]]. One of these is the "[[mallet (habit)|mallet]]", which is a small to medium-sized tree, usually of steep branching habit, sometimes fluted at the base of the trunk and often with a conspicuously dense, [[terminal]] crown. It is the habit usually of mature healthy specimens of ''Eucalyptus occidentalis'', ''E. astringens'', ''E. spathulata'', ''E. gardneri'', ''E. dielsii'', ''E. forrestiana'', ''E. salubris'', ''E. clivicola'' and ''E. ornata''. The smooth [[bark]] of mallets often has a satiny sheen and may be white, cream, grey, green or copper.
Another habit category used in Western Australia is the "[[marlock]]". This has been variously applied but Brooker & Hopper (2001) defined the term and restricted the use to describe the more or less pure stands of short, erect, thin-stemmed "trees" that do not produce [[lignotuber]]s. These are easily seen and recognised in stands of ''E. platypus'', ''E. vesiculosa'' and the unrealted ''E. stoatei''. The marlock is distinguished from mallets which are taller and have a characteristic steep branching habit. The origin and use of the term "morrel" is somewhat obscure and appears to apply to trees of the western Australian wheatbelt and [[goldfields]] which have a long, straight trunk, completely rough barked. It is now used mainly for ''E. longicornis'' (Red Morell) and ''E. melanoxylon'' (Black Morrel).
Tree sizes follow the [[Convention (norm)|convention]] of:
:*Small - to 10 metres in height
:*Medium sized - 10 to 30 metres in height
:*Tall - 30 to 60 metres in height
:*Very Tall - over 60 metres in height
=== Leaves ===
Nearly all ''Eucalyptus'' are [[evergreen]] but some tropical species lose their leaves at the end of the dry season. As in other members of the [[Myrtaceae|Myrtle]] family, ''Eucalyptus'' leaves are covered with oil glands. The copious oils produced are an important feature of the genus.
[[Image:Eucalyptus tetragona - glaucous leaves close.jpg|right|thumb|180px|''[[Eucalyptus tetragona]]'', showing glaucous leaves & stems]]
The leaves on a mature ''Eucalyptus'' plant are commonly [[lanceolate]], [[Leaf#Characteristics of the petiole|petiolate]], apparently [[Leaf#Arrangement on the stem|alternate]] and waxy or glossy green. In contrast the leaves of seedlings are frequently [[Leaf#Arrangement on the stem|opposite]], [[Leaf#Characteristics of the petiole|sessile]] and [[Leaf#Surface of the leaf|glaucous]]. However there are numerous exceptions to this pattern. Many species such as ''[[Eucalyptus melanophloia|E. melanophloia]]'' and ''E. setosa'' retain the juvenile leaf form even when the plant is reproductively mature. Some species such as ''[[Eucalyptus macrocarpa|E. macrocarpa]]'', ''[[Eucalyptus rhodantha|E. rhodantha]]'' and ''[[Eucalyptus. crucis|E. crucis]]'' are sought after ornamentals due to this lifelong juvenile leaf form. A few species such as ''[[Eucalyptus petraea|E. petraea]]'', ''[[Eucalyptus dundasii|E. dundasii]]'' and ''[[E. lansdowneana]]'' have shiny green leaves throughout their life cycle. ''[[Eucalyptus caesia|E. caesia]]'' exhibits the opposite pattern of leaf development to most ''Eucalyptus'', with shiny green leaves in the seedling stage and dull, glaucous leaves in mature crowns. The contrast between juvenile and adult leaf phases is valuable in field identification.
Four leaf phases are recognised in the development of a ''Eucalyptus'' plant - the ‘seedling’, ‘juvenile’, ‘intermediate’ and ‘adult’ phases. However there is no definite transitional point between the phases. The intermediate phase, when the largest leaves are often formed, links the juvenile and adult phases.<ref name=FieldGuide>Brooker & Kleinig (2001)</ref> Most species do not flower until adult foliage starts to appear; ''E. cinerea'' and ''E. perriniana'' are notable exceptions.
In all except a few species the leaves form in pairs on opposite sides of a square stem, consecutive pairs being at right angles to each other (decussate). In some narrow-leaved species - for example ''[[Eucalyptus oleosa|E. oleosa]]'' - the seedling leaves after the second leaf pair are often clustered in a detectable spiral arrangement about a five sided stem. After the spiral phase, which may last from several to many nodes, the arrangement reverts to decussate by the absorption of some of the leaf bearing faces of the stem. In those species with opposite adult foliage the leaf pairs, which have been formed opposite at the stem apex, become separated at their bases by unequal elongation of the stem to produce the apparently alternate adult leaves.
[[Image:Eucalyptus leucoxylon1.jpg|left|thumb|''[[Eucalyptus leucoxylon]]'' var. '''‘Rosea’''' showing flowers & buds with operculum present]]
[[Image:E.sideroxylon, branchlets, stems, leaves, capsules & buds.jpg|right|thumb|''Eucalyptus sideroxylon'', showing fruit (capsules) & buds with operculum present.]]
=== Flowers ===
The most readily recognisable characteristics of Eucalyptus species are its distinctive flowers and fruit (capsule). Flowers have numerous fluffy stamens which may be white, cream, yellow, pink or red; in bud the stamens are enclosed in a cap known as an operculum which is composed of the fused sepals or petals or both. Thus flowers have no petals, decorating themselves instead with the many showy stamens. As the stamens expand the operculum is forced off, splitting away from the cup-like base of the flower; this is one of the features that that unites the genus. The name Eucalyptus, from the Greek words ''eu-'', well, and ''kaluptos'', cover, meaning "well-covered", describes the operculum. The woody fruits or capsules, known as gumnuts, are roughly cone-shaped and have valves at the end which open to release the seeds. Most species do not flower until adult foliage starts to appear; ''[[Eucalyptus cinerea]]'' and ''[[Eucalyptus perriniana]]'' are notable exceptions.
[[Image:Eucalyptus tree.jpg|thumb|200px|left|''Eucalyptus sp'' in [[East Gippsland]], [[Victoria, Australia]], showing ‘ribbon’ bark form.]]
[[Image:Eucalyptus sideroxylon - bark.jpg|left|thumb|200px|The dark, fissured ‘Ironbark’ bark of ''[[Eucalyptus sideroxylon]]'']]
=== Bark ===
The appearance of ''Eucalyptus'' bark will vary with the age of the plant, the manner of bark shed, the length of the bark fibres, the degree of furrowing, the thickness, the hardness and the colour. All mature eucalypts put on an annual layer of bark, which contributes to the increasing diameter of the stems. In some species the outermost layer dies and is annually deciduous either in long strips (as in ''[[Eucalyptus sheathiana]]'') or in variably sized flakes (''[[Eucalyptus diversicolor]]'', ''[[Eucalyptus cosmophylla]]'' or ''[[Eucalyptus cladocalyx]]''). These are the gums or smooth-barked species. The gum bark may be dull, shiny or satiny (as in ''[[Eucalyptus ornata]]'') or matt (''[[Eucalyptus cosmophylla]]''). In many species the dead bark is retained. Its outermost layer gradually fragments with weathering and sheds without altering the essentially rough barked nature of the trunks or stems - for example ''[[Eucalyptus marginata]]'', ''[[Eucalyptus jacksonii]]'', ''[[Eucalyptus obliqua]]'' and ''[[Eucalyptus porosa]]''.
[[Image:Eucalyptus deglupta-trees.jpg|thumb|right|200px|The extraordinary coloured bark of ''[[Eucalyptus deglupta]]'' native to South East Asia]]
Many species are ‘half-barks’ or ‘blackbutts’ in which the dead bark is retained in the lower half of the trunks or stems - for example, ''[[Eucalyptus brachycalyx]]'', ''[[Eucalyptus ochrophloia]]'' and ''[[Eucalyptus occidentalis]]'' - or only in a thick, black accumulation at the base, as in ''[[Eucalyptus clelandii]]''. Some species in this category - for example - ''[[Eucalyptus youngiana]]'' - the rough basal bark is very ribbony at the top, where it gives way to the smooth upper stems. The smooth upper bark of the half barks and that of the completely smooth-barked trees and mallees can produce remarkable colour and interest, for example ''[[Eucalyptus deglupta]]''.<ref name=FieldGuide/>
[[Image:Eucalyptus bark.jpg|right|thumb|200px|The '''box''' bark of ''[[Eucalyptus quadrangulata]]'', or '''White Box''']]
====Bark characteristics====
* '''Stringybark''' - consists of long-fibres and can be pulled off in long pieces. It is usually thick with a spongy texture.
* '''Ironbark''' - is hard, rough and deeply furrowed. It is impregnated with dried kino (a [[Sap (plant)|sap]] exuded by the tree) which gives a dark red or even black colour.
* '''Tessellated''' - bark is broken up into many distinct flakes. They are [[cork (material)|corkish]] and can flake off.
* '''Box''' - has short fibres. Some also show tessellation.
* '''Ribbon''' - this has the bark coming off in long thin pieces but still loosely attached in some places. They can be long ribbons, firmer strips or twisted curls.
==Species and hybridism==
There are over 700 [[species]] of Eucalyptus; refer to the '''[[List of Eucalyptus species]]''' for a comprehensive list of species. It is believed that all eucalypts are related either closely or remotely. Some have [[divergent evolution|diverged]] from the mainstream of the [[genus]] to the extent that they are quite isolated [[genetics|genetically]] and are able to be recognised by only a few relatively [[invariant]] [[characteristics]]. Most, however, may be regarded as belonging to large or small groups of related species, which are often in [[geographical]] contact with each other and between which [[gene]] exchange still occurs. In these situations many species will appear to grade into one another and intermediate forms are common. In other words, some species are relatively fixed genetically, as expressed in their [[morphology (biology)|morphology]], while others have not diverged completely from their nearest relatives.
Hybrid individuals have not always been recognised as such on first collection and some have been named as new species, such as ''E. chrysanth''a (''E. preissiana'' × ''E. sepulcralis'') and ''E.'' "rivalis" (''E. marginata'' × ''E. megacarpa''). Hybrid combinations are not particularly common in the field, but some other published species have been suggested to be hybrid combinations and are frequently seen in Australia. For example, ''E. erythrandra'' is believed to be ''E. angulosa'' × ''E. teraptera'' and due to its wide distribution is often referred to in texts.<ref name=FieldGuide/>
==Related genera==
A small genus of similar trees, ''[[Angophora]]'', has also been known since the [[18th century]]. In [[1995]] new evidence, largely genetic, indicated that some prominent ''Eucalyptus'' species were actually more closely related to ''Angophora'' than to the other eucalypts; they were split off into the new [[genus]] ''[[Corymbia]]''. Although separate, the three groups are allied and it remains acceptable to refer to the members of all three genera ''Angophora'', ''Corymbia'' and ''Eucalyptus'' as "eucalypts". The coolibah trees, referred to in [[Waltzing Matilda]], are ''Eucalyptus'' ''[[Eucalyptus coolabah|E. coolabah]]'' and ''[[Eucalyptus microtheca|E. microtheca]]''.
[[Image:Tasmania logging 16 Styx a tree in danger.jpg|thumb|right|200px|''Eucalyptus regnans'' exceeding 80 metres, in an area of extensive logging, Tasmania]]
==Tall timber==
Today, specimens of the Australian Mountain Ash, ''[[Eucalyptus regnans]]'', are among the tallest trees in the world at up to 92 metres in height <ref>{{cite web | url=http://www.forestrytas.com.au/forestrytas/tasfor/tasforests_12/tasfor_12_09.pdf | media=PDF | title=Tasmania's Tallest Trees | author=J.E. Hickey, P. Kostoglou, G.J. Sargison | publisher=Forestry Tasmania | accessdate=2005-01-27}}</ref> and the tallest of all flowering plants ([[Angiosperms]]); taller trees such as the [[Coast Redwood]] are all [[conifer]]s ([[Gymnosperms]]). There is credible evidence however that at the time of European settlement of Australia some Mountain Ash were indeed the tallest plants in the world.
==Tolerance==
Most eucalypts are not tolerant of frost, or only tolerate light frosts down to -3°C to -5°C; the hardiest, are the so-called Snow Gums such as ''[[Eucalyptus pauciflora]]'' which is capable of withstanding cold and frost down to about -20°C. Two sub-species, ''E. pauciflora subsp. niphophila'' and ''E. pauciflora subsp. debeuzevillei'' in particular are even hardier and can tolerate even quite severe [[winter]]s. Several other species, especially from the high plateau and mountains of central [[Tasmania]] such as ''[[Eucalyptus coccifera]]'', ''[[Eucalyptus subcrenulata]]'', and ''[[Eucalyptus gunnii]]'', have produced extreme cold hardy forms and it is seed procured from these [[genetics|genetically]] hardy strains that are planted for ornament in colder parts of the world.
==Animal relationships==
[[Image:Koala-ag1.jpg|thumb|left|220px|''Phascolarctos cinereus'' [[Koala]] eating ''eucalyptus'' leaves]]
An [[essential oil]] extracted from eucalyptus leaves contains compounds that are powerful natural disinfectants and which can be toxic in large quantities. Several [[marsupial herbivore]]s, notably [[koala]]s and some [[possum]]s, are relatively tolerant of it. The close correlation of these oils with other more potent toxins called formylated [[phloroglucinol]] compounds allows koalas and other [[marsupial]] species to make food choices based on the smell of the leaves. However, it is the formylated phloroglucinol compounds that are the most important factor in choice of leaves by koalas. Eucalyptus flowers produce a great abundance of [[nectar]], providing food for many [[pollinator]]s including [[insect]]s, birds, [[Chiroptera|bat]]s and [[possum]]s. Despite the fact that eucalyptus trees are well-defended from herbivores by their toxic essential oils they do have their share of insect pests, such as the Eucalyptus [[Longhorn Beetle|Longhorn Borer]] [[Beetle]], ''[[Phoracantha semipunctuata]]'', or the aphid-like [[psyllid]]s known as "[[Bell Miner|bell lerps]]," both of which have become established as pests throughout the world wherever eucalypts are cultivated.
{{See|list of Lepidoptera which feed on Eucalyptus}}
==Hazards==
[[Image:Log embedded in white box.jpg|thumb|200px|right|A fallen log is embedded in a ''[[Eucalyptus albens]]''. This formation is the [[CODIT|tree's response]].]]
Some species of Eucalyptus have a habit of dropping entire branches off as they grow. Eucalyptus forests are littered with dead branches. The Australian Ghost Gum ''[[Eucalyptus papuana]]'' is also termed the "widow maker," due to the high number of pioneer tree-felling workers who were killed by falling branches. Many people have been killed as they camped underneath the trees. It is thought the trees shed very large branches to conserve water during periods of drought. This may be the real reason behind the [[drop bear]] story told to children - the idea is to keep them away from being under dangerous branches.
==Fire==
On warm days vapourised eucalyptus oil rises above the [[The Bush|bush]] to create the characteristic distant blue haze of the Australian landscape. Eucalyptus oil is highly flammable (trees have been known to explode<ref>{{Cite web |url=http://library.csustan.edu/bsantos/section3.htm |title=Section Three: Problems, Cares, Economics, and Species |work=The Eucalyptus of California |first=Robert L. |last=Santos |publisher=California State University |year=1997}}</ref><ref>{{Cite web |url=http://www.robertsward.com/eucmore.htm |title=Eucalytus Roulette (con't) |publisher=Robert Sward: Poet, Novelist and Workshop Leader }}</ref>) and [[bush fire]]s can travel easily through the oil-rich air of the tree crowns. The dead bark and fallen branches are also flammable. Eucalypts are well adapted for periodic fires, in fact most species are dependent on them for spread and [[regeneration (biology)|regeneration]]. {{Fact|date=June 2007}} They do this via [[lignotuber]]s, epicormic buds under the bark and from fire-germinated seeds sprouting in the ashes. {{Fact|date=June 2007}}
[[Image:Eucalyptus forest2.jpg|thumb|280px|left|Eucalyptus forest in a state of regeneration]]
Eucalypts originated between 35 and 50 million years ago, not long after [[Australia-New Guinea]] separated from [[Gondwana]], their rise coinciding with an increase in fossil charcoal deposits (suggesting that fire was a factor even then), but they remained a minor component of the Tertiary rainforest until about 20 million years ago when the gradual drying of the continent and depletion of soil nutrients led to the development of a more open forest type, predominantly ''[[Casuarina]]'' and ''[[Acacia]]'' species. With the arrival of the first humans about 50 thousand years ago fires became much more frequent and the fire-loving eucalypts soon came to account for roughly 70% of Australian forest.
Eucalypts regenerate quickly after [[fire]]. After the [[Canberra bushfires of 2003]], hectares of imported species were killed, but in a matter of weeks the gum trees were putting out suckers and looking generally healthy. {{Fact|date=June 2007}}
The two valuable timber trees, Alpine Ash ''[[Eucalyptus delegatensis|E. delegatensis]]'' and Mountain Ash ''[[Eucalyptus regnans|E. regnans]]'', are killed by fire and only regenerate from seed. The same 2003 bushfire that had little impact on forests around [[Canberra]] resulted in thousands of hectares of dead ash forests. However, a small amount of ash survived and put out new suckers as well. There has been some debate as to whether to leave the stands, or attempt to harvest the mostly undamaged timber, which is increasingly recognised as a damaging practice.
==Cultivation and uses==
[[Image:NamadgiTree.jpg|thumb|''[[Eucalyptus niphophila]]'' in [[Namadgi National Park]]]]
Eucalyptus have many uses which have made them [[economically]] important trees. Perhaps the [[Karri]] and the [[Eucalyptus melliodora|Yellow box]] varieties are the best known. Due to their fast growth the foremost benefit of these trees is the wood. They provide many desirable characteristics for use as ornament, timber, firewood and [[pulpwood]]. Fast growth also makes eucalypts suitable as [[windbreak]]s. Eucalypts draw a tremendous amount of water from the soil through the process of [[transpiration]]. They have been planted (or re-planted) in some places to lower the water table and reduce [[soil salination]]. Eucalypts have also been used as a way of reducing [[malaria]] by draining the soil in Algeria, Sicily<ref>{{cite web | url=http://www.botanical.com/botanical/mgmh/e/eucaly14.html | title=A Modern Herbal:Eucalyptus | author=Mrs. M. Grieve | accessdate=2005-01-27}}</ref> and also in Europe and California<ref>{{cite web | author=Santos, Robert L | url=http://wwwlibrary.csustan.edu/bsantos/section2.htm#FIGHTING | title=Section Two: Physical Properties and Uses |work=The Eucalyptus of California | publisher=California State University |year=1997}}</ref>. Drainage removes swamps which provide a habitat for [[mosquito]] [[larva]]e, but such drainage can also destroy ecologically productive areas.
[[Eucalyptus oil]] is readily [[steam distillation|steam distilled]] from the leaves and can be used for cleaning, deodorising, and in very small quantities in [[food]] supplements; especially [[sweets]], cough drops and decongestants. Eucalyptus oil has insect repellent properties (Jahn 1991 a, b; 1992), and is an active ingredient in some commercial mosquito repellents (Fradin & Day 2002).
The [[nectar (plant)|nectar]] of some eucalyptus produces high quality [[monofloral honey]]. The ghost gum's leaves were used by [[Indigenous Australians|Aborigines]] to catch fish. Soaking the leaves in water releases a mild tranquilliser which stuns fish temporarily. Eucalyptus is also used to make the [[digeridoo]], a musical wind instrument made popular by the Aborigines of Australia.
All parts of the eucalyptus may be used to make plant [[dyes]] that are substantive on protein fibres ([[silk]] and [[wool]]) simply by processing the plant part with [[water]]{{Fact|date=August 2007}}. Colours to be achieved range from yellow and orange through green, tan, chocolate and deep rust red. The material remaining after processing can be safely used as mulch{{Fact|date=August 2007}}.
== History ==
[[Image:Sir Joseph Banks, president of the Royal Society.jpg|left|thumb|Sir Joseph Banks]]Although Eucalypts must have been seen by the very early European explorers and collectors, no botanical collections of them are known to have been made until [[1770]] when [[Joseph Banks]] and [[Daniel Solander]] arrived at [[Botany Bay]] with [[Captain James Cook]]. There they collected specimens of ''E. gummifera'' and later, near the [[Endeavour River]] in northern ''Queensland'', they collected ''E. platyphylla''; neither of these species was named as such at the time.
In [[1777]], on Cook's third expedition, David Nelson collected a eucalypt on [[Bruny Island]] in southern [[Tasmania]]. This specimen was taken to the [[British Museum]] in [[London]], and it was named ''Eucalyptus obliqua'' by the French botanist [[L'Héritier]], who was working in London at the time. He coined the generic name from the Greek roots ''eu'' and ''calyptos'', meaning "well" and "covered" in reference to the [[operculum (botany)|operculum]] of the flower bud. This organ protects the developing flower parts as the flower develops and is shed by the pressure of the emerging [[stamens]] at flowering.
The name ''obliqua'' was derived from the Latin ''obliquus'', meaning "oblique" which is the [[botany|botanical]] term describing a [[leaf]] base where the two sides of the leaf blade are of unequal length and do not meet the petiole at the same place.
In naming ''E. obliqua'', [[Charles Louis L'Héritier de Brutelle|L'Héritier]] caused to be perpetuated, most likely by accident, a feature common to all eucalypts - the operculum. In his choice of a specific name, he recognised not only the characteristic feature of ''E. obliqua'', but one common to many other species as well. ''E. obliqua'' was published in [[1788]]-89 and coincides with the date of the first official European settlement of Australia.
[[Image:Von mueller.jpg|right|thumb|Ferdinand von Mueller]]
Between 1788-89 and the turn of the nineteenth century several more species of ''Eucalyptus'' were named and published. Most of these were by the English botanist [[James Edward Smith]] and most were, as might be expected, trees of the [[Sydney]] region. These include the economically valuable ''E. pilularis'', ''E. saligna'' and ''E. tereticornis''.
The nineteenth century saw the endeavours of several of the great botanists in Australian history, particularly [[Ferdinand von Mueller]], whose work on eucalypts contributed greatly to the first comprehensive account of the genus in [[George Bentham]]'s ''Flora Australiensis'' in 1867 - which today remains the only complete Australian flora. The account in Bentham is the most important early systematic treatment of the genus. Bentham divided the genus into five series whose distinctions were based on characteristics of the stamens, particularly the anthers (Mueller, 1879-84), elborated further by Joseph Henry Maiden (1903-33), and taken even further by William Faris Blakely (1934). By this time the anther system had become too complex to be workable and more recent systematic work has concentrated on the characteristics of buds, fruits, leaves and bark.
The first endemic Western Australian ''Eucalyptus'' to be collected and subsequently named was the yate (''E. cornuta'') by the French botanist [[La Billardiére]], who collected in what is now the [[Esperance]] area in [[1792]].<ref name=FieldGuide/>
==Plantation and ecological problems==
''Eucalyptus'' was first introduced to the rest of the world by [[Joseph Banks|Sir Joseph Banks]], [[botanist]], on the [[James Cook|Cook]] expedition in 1770. They have subsequently been introduced to many parts of the world, notably [[California]], [[Brazil]], [[Ecuador]], [[Colombia]], [[Ethiopia]], [[Morocco]], [[Portugal]], [[South Africa]], [[Israel]], [[Galicia (Spain)|Galicia]] and [[Chile]]. In [[Spain]] they have been planted in pulpwood [[plantation]]s, replacing native [[oak]] woodland. ''Eucalyptus'' are the basis for several industries, such as sawmilling, pulp, charcoal and others. Several species have become [[invasive species|invasive]] and are causing major problems for local ecosystems.
===California===
In the 1850s many Australians traveled to [[California]] to take part in the [[California Gold Rush]]. Much of California has a similar climate to parts of Australia and some people got the idea of introducing eucalypts. By the early 1900s thousands of acres of eucalypts were planted with the encouragement of the state government. It was hoped that they would provide a renewable source of timber for construction and furniture making. However, this did not happen, partly because the trees were cut when they were too young and partly because the Americans did not know how to process the cut trees to prevent the wood from twisting and splitting.<ref>{{Cite web |url=http://www.library.csustan.edu/bsantos/euctoc.htm |work=The Eucalyptus of California |first=Robert L. |last=Santos |publisher=California State University |work=The Eucalyptus of California |title=Seeds of Good or Seeds of Evil? |year=1997}}</ref>
One way in which the eucalyptus, mainly the blue gum ''E. globulus'', proved valuable in California was in providing windbreaks for highways, orange groves, and other farms in the mostly treeless central part of the state. They are also admired as shade and ornamental trees in many cities and gardens.
''Eucalyptus'' forests in California have been criticized because they compete with native plants and do not support native animals. Fire is also a problem. The 1991 [[Oakland Hills firestorm]] which destroyed almost 3,000 homes and killed 25 people was partly fueled by large numbers of eucalypts in the area close to the houses.<ref>{{Cite web |last=Williams |first=Ted |title=America's Largest Weed |publisher=Audubon Magazine |month=January |year=2002 |url=http://magazine.audubon.org/incite/incite0201.html}}</ref>
In some parts of California eucalypt forests are being removed and native trees and plants restored. Individuals have also illegally destroyed some trees and are suspected of introducing insect pests from Australia which attack the trees.<ref>{{Cite web |title=Tree Wars: The Secret Life of Eucalyptus |first=Heather |last=Henter |month=January |year=2005 |publisher=University of California, San Diego |work=Alumni |url=http://alumni.ucsd.edu/magazine/vol2no1/features/wars.htm}}</ref>
===Brazil===
In 1910 ''Eucalyptus'' was introduced to Brazil for [[timber]] substitution and the [[charcoal|vegetal coal]] industry. It has adpated very well to the local environmental conditions{{Fact|date=August 2007}} and today there are around 5 million hectares planted. The wood produced by the tree is highly appreciated by the charcoal and pulp and paper industries. The short rotation allows a larger wood production and supply wood for several other activities, helping to preserve the native forests from logging. When well managed the plantations are sustainable and the soil can sustain endless replantations. Eucalyptus plantations are also used as [[windbreak|wind breaks]].
===Ethiopia===
This species was introduced to [[Ethiopia]] in either 1894 or 1895, either by Emperor [[Menelik II of Ethiopia|Menelik II]]'s French advisor Mondon-Vidailhet or the Englishman Captain O'Brian. Due to massive deforestation around his new capital city [[Addis Ababa]] caused by a growing appetite for [[fire wood]], Emperor [[Menelik II of Ethiopia|Menelik II]] endorsed its planting around that city; according to [[Richard R.K. Pankhurst]], "The great advantage of the eucalypts was that they were fast growing, required little attention and when cut down grew up again from the roots; it could be harvested every ten years. The tree proved successful from the onset".<ref>Pankhurst p. 246</ref> Plantations of eucalypts spread from the capital to other growing urban centers such as [[Debre Marqos]]; Pankhurst reports that the most common species found in Addis Ababa in the mid-1960s was ''[[Eucalyptus globulus|E. globulus]]'', although he also found ''[[Eucalyptus melliodora|E. melliodora]]'' and ''[[Eucalyptus rostrata|E. rostrata ]]'' in significant numbers. David Buxton, writing of central Ethiopia in the mid-1940s, observed that eucalyptus trees "have become an integral -- and a pleasing -- element in the [[Shewa|Shoan]] landscape and has largely displaced the slow-growing native 'cedar' or juniper."<ref>David Buxton, ''Travels in Ethiopia'', second edition (London: Benn, 1957), p. 48</ref>
Popular opposition soon developed that in 1913 a proclamation was issued ordering a partial destruction of all standing trees, and their replacement with [[mulberry]] trees. "The proclamation," Pankhurst notes, "however remained a dead letter; there is no evidence of eucalypts being uprooted, still less of mulberry trees being planted."<ref>Pankhurst p. 247</ref> The eucalypt remains a defining feature of Addis Ababa.
==Photo gallery==
<gallery>
<!-- Please only add pictures where the species or variety of tree has been identified and the location - there are many varieties of eucalyptus and it is not encyclopaedic to say merely "eucalyptus"-->
Image:Eucalyptus forest.jpg|Eucalyptus forest in [[East Gippsland Shire|East Gippsland]], [[Victoria (Australia)|Victoria]]. Mostly ''Eucalyptus albens'' (white box).
Image:Eucalyptus forest3.jpg|Eucalyptus forest in [[East Gippsland Shire|East Gippsland]], [[Victoria (Australia)|Victoria]]. Mostly ''Eucalyptus albens'' (white box).
Image:Eucalypt forest.jpg|Eucalyptus forest in [[East Gippsland Shire|East Gippsland]], [[Victoria (Australia)|Victoria]]. Mostly ''Eucalyptus albens'' (white box).
Image:Eucalyptustreewithsun.JPG|A eucalyptus tree with the sun shining through its branches.
Image:Applebox.JPG|''Eucalyptus bridgesiana'' (Apple box) on [[Red Hill, Australian Capital Territory]].
image:euc.uk.600pix.jpg|''Eucalyptus gunnii'' planted in southern [[England]]. The lower part of the trunk is covered in [[ivy]].
Image:Eucalyptus cinera x pulverulenta.jpg|''Eucalyptus cinerea'' x ''pulverulenta'' - National Botanical Gardens Canberra
Image:Eucalyptus gall.jpg|Eucalyptus Pink Waxy Scale Insects
Image:CPonte Eucalyptus.jpg|''Eucalyptus grandis''. Province of Buenos Aires, Argentina.
Image:Eucalipto Galicia.JPG|Eucalyptus plantation in [[Galicia (Spain)|Galicia]] in Northwest [[Spain]]
Image:Eucalyptus rubida.jpg| ''Eucalyptus rubida'' ([[Candlebark gum]]) in [[Burra, New South Wales]].
Image:2007 0731klklk0151.JPG|This tree in [[Heathcote National Park]] has a serious problem.
</gallery>
==Notes==
{{Reflist|2}}
==References==
* {{Cite book |last=Brooker |first=M.I.H. |coauthors=Kleinig, D.A. |title=Field Guide to Eucalyptus |publisher=Bloomings |location=Melbourne |year=2001}}
*{{Cite book |first=Richard |last=Pankhurst |title=Economic History of Ethiopia |location=Addis Ababa |publisher=Haile Selassie I University |year=1968}}
==External links==
{{sisterlinks}}
* [http://www.anbg.gov.au/cpbr/cd-keys/Euclid/sample/html/index.htm EUCLID Sample], CSIRO
* [http://farrer.riv.csu.edu.au/ASGAP/eucalypt.html The Eucalyptus Page]
* [http://plantnet.rbgsyd.nsw.gov.au/PlantNet/Euc/ EucaLink]
* [http://www.dn.com.au Currency Creek Arboretum - Eucalypt Research]
*[http://www.cirrusimage.com/tree_Eucalyptus.htm ''Eucalyptus globulus''] Diagnostic photos: tree, leaves, bark
*[http://www.hort.purdue.edu/newcrop/duke_energy/Eucalyptus.html Handbook of Energy Crops] Duke, James A. 1983.
*[http://www.library.csustan.edu/bsantos/euctoc.htm The Eucalyptus of Califonia: Seeds of Good or Seeds of Evil?] Santos, Robert. 1997 Denair, CA : Alley-Cass Publications
*[http://www.geocities.com/RainForest/7813/euca_1.htm Impacts of Monoculture: The Case of Eucalyptus Plantations in Thailand] a paper for the Monocultures: Environmental and Social Effects and Sustainable Alternatives Conference, June 2-6 1996, Songkhla, Thailand, prepared by Areerat Kittisiri, Rural Reconstruction and Friends Association (RRAFA), Bangkok, Thailand
===Medicinal resources, eucalyptus essential oil===
* http://www.botanical.com/botanical/mgmh/e/eucaly14.html
* http://www.henriettesherbal.com/eclectic/bpc1911/eucalyptus_oleu.html
[[Category:Myrtales of Australia]]
[[Category:Medicinal plants]]
[[Category:Eucalyptus| Eucalyptus]]