Difference between revisions of "Eucalyptus" - New World Encyclopedia

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{{Taxobox_begin | color = lightgreen| name = Eucalyptus}}
 
{{Taxobox_begin | color = lightgreen| name = Eucalyptus}}
 
{{Taxobox_image | image = [[Image:Eucalyptus flowers2.jpg|250px]]| caption = ''Eucalyptus melliodora'' foliage and flowers}}
 
{{Taxobox_image | image = [[Image:Eucalyptus flowers2.jpg|250px]]| caption = ''Eucalyptus melliodora'' foliage and flowers}}
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{{Taxobox_regnum_entry | taxon = [[Plant]]ae}}
 
{{Taxobox_regnum_entry | taxon = [[Plant]]ae}}
 
{{Taxobox_divisio_entry | taxon = [[Flowering plant|Magnoliophyta]]}}
 
{{Taxobox_divisio_entry | taxon = [[Flowering plant|Magnoliophyta]]}}
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{{Taxobox_classis_entry | taxon = [[Magnoliopsida]]}}
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{{Taxobox_classis_entry | taxon = Magnoliopsida}}
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{{Taxobox_ordo_entry | taxon = [[Myrtales]]}}
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{{Taxobox_ordo_entry | taxon = Myrtales}}
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{{Taxobox_familia_entry | taxon = [[Myrtaceae]]}}
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{{Taxobox_familia_entry | taxon = Myrtaceae}}
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{{Taxobox genus entry | taxon = '''''Eucalyptus'''''}}<br/>{{Taxobox authority new | authority = [[Charles Louis L'Héritier de Brutelle|L'Hér.]]}}
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{{Taxobox genus entry | taxon = '''''Eucalyptus'''''}}<br/>{{Taxobox authority new | authority = Charles Louis L'Héritier de Brutelle|L'Hér.}}
 
{{Taxobox_end_placement}}
 
{{Taxobox_end_placement}}
 
{{Taxobox_section_subdivision | color = lightgreen| plural_taxon = Species}}
 
{{Taxobox_section_subdivision | color = lightgreen| plural_taxon = Species}}
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About 700; see the [[List of Eucalyptus species]]
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About eight hundred
 
{{Taxobox_end}}
 
{{Taxobox_end}}
  
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'''''Eucalyptus''''' is a diverse [[genus]] of [[tree]]s (rarely shrubs), the members of which dominate the tree flora of [[Australia]]. There are more than 700 species of ''Eucalyptus'', mostly native to Australia, with a very small number found in adjacent parts of [[New Guinea]] and [[Indonesia]]. Eucalypts can be found in almost every part of the continent, adapted to all of Australia's climatic conditions; in fact, no other continent is so characterised by a single genus of tree as Australia is by eucalyptus. Many, but far from all, are known as '''gum trees'''; other names for various species include '''[[mallee]]''', '''box''', '''[[ironbark]]''', '''[[stringybark]]''', and '''ash'''.
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'''''Eucalyptus''''' is a diverse genus of [[tree]]s (rarely shrubs), the members of which dominate the tree flora of [[Australia]]. There are more than eight hundred [[species]] of Eucalyptus, mostly native to Australia, with a very small number of native species found in parts of adjacent [[New Guinea]] and [[Indonesia]] and one as far away as the [[Philippines]]. The Eucalyptus genus is part of the Myrtle family (Myrtaceae), which is a family of dicotyledon [[plant]]s&mdash;[[flowering plant]]s whose seed typically contains two embryonic leaves or cotyledons.
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Eucalypts, as they are also called, can be found in almost every part of the Australian continent, adapted to all of Australia's climatic conditions; in fact, no other continent is so characterized by a single genus of tree as Australia is by Eucalyptus.  
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On the other hand, the deliberate introduction of eucalyptus to other parts of the world, as invasive species, has sometimes resulted in unintended consequences, including deadly wildfires, reduced habitat for native plants and [[animal]]s, and reduction of valuable [[wetland]]s. They serve as a reminder that nature involves many complex interactions, formed over millions of years, and human interventions must not be pursued lightly.
  
 
==Description==
 
==Description==
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The most readily recognisable characteristics of ''Eucalyptus'' species are the distinctive [[flower]]s and [[fruit]]s. The name ''Eucalyptus'' means "well-covered"; it describes the bud cap (technically called an [[Operculum (Botany)|operculum]]). This cap forms from modified [[petal]]s and falls off as the flower opens. Thus flowers have no petals, decorating themselves instead with many showy [[stamen]]s. The woody fruits are roughly cone-shaped and have valves at the end which open to release the seeds.
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[[Image:Eucalyptus leucoxylon1.jpg|thumb|200px|''Eucalyptus leuxoxylon'']]
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The most readily recognizable characteristics of Eucalyptus species are the distinctive [[flower]]s and [[fruit]]s. The name Eucalyptus means "well-covered"; it describes the bud cap (technically called an operculum). This cap forms from modified [[petal]]s and falls off as the flower opens. Thus flowers have no petals, decorating themselves instead with many showy [[stamen]]s. The woody fruits are roughly cone-shaped and have valves at the end that open to release the seeds.
  
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Nearly all eucalypts are [[evergreen]] but some tropical species lose their leaves at the end of the dry season. As in other members of the [[Myrtle]] family, eucalypt leaves are covered with oil glands. The copious oils produced are an important feature of the genus.  Eucalypts also exhibit [[leaf dimorphism]]. When young, their leaves are opposite, oval to roundish, and occasionally without a petiole. When one to a few years old, the leaves become alternate, lanceolate to falcate ([[sickle]]-shaped), quite slender and pendulous with longer petioles. The adult leaves of most species, as well as the juvenile leaves of some, are the same on both sides, lacking the distinction between upper and lower surfaces shown by the leaves of most plants. Most species do not flower until adult foliage starts to appear; ''E. cinerea'' and ''E. perriniana'' are notable exceptions.
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A small genus of similar trees, ''Angophora'', has also been known since the eighteenth century. In 1995, new evidence, largely [[genetics|genetic]], indicated that some prominent eucalypt species were actually more closely related to ''Angophora'' than to 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."
  
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The [[bark]] dies annually and species can be roughly grouped based on its appearance. In smooth-barked trees most of the bark is shed, leaving a smooth surface that is often colourfully mottled. With rough-barked trees the dead bark persists on the tree and dries out. Many trees, however, have smooth bark at the top but rough bark on the trunk or its bottom. The types of rough bark is often used to broadly label a group of eucalypts. They are:
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Nearly all eucalypts are [[Tree#evergreen|evergreen]], but some tropical species lose their leaves at the end of the dry season. As in other members of the Myrtle family, eucalypt leaves are covered with oil glands. The copious oils produced are an important feature of the genus. Eucalypts also exhibit leaf dimorphism. When young, their leaves are opposite, oval to roundish, and occasionally without a petiole. When one to a few years old, the leaves become alternate, lanceolate to falcate (sickle-shaped), quite slender, and pendulous with longer petioles. The adult leaves of most species, as well as the juvenile leaves of some, are the same on both sides, lacking the distinction between upper and lower surfaces shown by the leaves of most plants. Most species do not flower until adult foliage starts to appear; ''E. cinerea'' and ''E. perriniana'' are notable exceptions.
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* '''Stringybark''' - consists of long-fibres and can be pulled off in long pieces. It is usually thick with a spongy texture.
 
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* '''Ironbark''' - is hard, rough and deeply furrowed. It is soaked with dried kino (a [[Sap (plant)|sap]] exuded by the tree) which gives a dark red or even black colour.
 
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* '''Tessellated''' - bark is broken up into many distinct flakes. They are corkish and can flake off.
 
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* '''Box''' - has short fibres. Some also show tessellation.
 
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* '''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.
 
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<!-- It'd be real nice to have a series of pics showing the different bark types —>
 
  
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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 eucalypt 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".
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Eucalyptus species have various types of [[bark]]. In smooth-barked trees, most of the bark is shed, leaving a smooth surface that is often colorfully mottled. With rough-barked trees the dead bark persists on the tree and dries out. Many trees, however, have smooth bark at the top but rough bark on the trunk or its bottom.  
  
 
{| align=right
 
{| align=right
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|[[Image:Eucalyptus gall.jpg|thumb|200px|Eucalyptus gall]]
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|[[Image:Eucalyptus.jpg|right|thumb|200px|A Eucalyptus tree]]
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|[[Image:Eucalyptus.jpg|right|thumb|250px|A eucalyptus tree]]
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|-
 
|-
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|[[Image:Eucalyptus02.jpg|thumb|200px|A Eucalyptus tree]]
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|[[Image:Eucalyptus bark.jpg|right|thumb|250px|The thick, protective bark of ''Eucalyptus quadrangulata'']]
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|-
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|[[Image:Eucalyptus bark.jpg|right|thumb|200px|The thick, protective bark of ''Eucalyptus quadrangulata'']]
 
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|[[Image:Eucalyptus forest2.jpg|thumb|200px|Eucalyptus Forest]]
 
 
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|}
  
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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; other taller trees such as the [[Coast Redwood]] are all [[conifer]]s. 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.
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Many eucalypts are called "gum trees" because of a sticky, gum-like substance they exude from their trunks. Some of the other common names for different eucalypts include:
  
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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 niphophila'' and ''E. pauciflora debeuzevillei'' in particular are even hardier and can tolerate even quite severe continental type [[winters]].
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*Apple - They look like apple trees (eg. ''Angophora bakeri'', "Narrow-leaved apple")
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*Ash - Their timber is similar to that of European ash trees (eg. ''E. regnans'', "Mountain ash")
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*Blackbutt - The lower bark is usually black due to past fires (eg. ''E. pilularis'', "Blackbutt")
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*Bloodwood - Timber often has pockets of a dark red gum called "kino" (eg. ''Corymbia eximia'', "Yellow bloodwood")
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*Box - The bark stays on the tree and is short fibered; plates of bark may shear off with age (eg. ''E. melliodora'' ("Yellow box")
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*Ironbark - The bark stays on the tree and is hard and deeply furrowed (eg. ''E. crebra'', "Narrow-leaved ironbark")
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*Mallee - Multi-stemmed trees, usually fairly short (eg. ''E. albida'', "White-leaved mallee")
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*Peppermint - The oil in the leaves smells like peppermint. (eg. ''E. dives'', "Broad-leaved peppermint")
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*Ribbon Gum - Bark is deciduous and is shed in long strips that hang from the branches (eg. ''E. viminalis'', "Ribbon gum")
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*Scribbly Gum - The smooth trunk is marked with "scribbles" caused by an [[insect]] larva (eg. ''E. sclerophylla'', "Scribbly gum")
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*Stringybark - Bark consists of long fibers that can be pulled off in "strings" (eg. ''E. eugenioides'', "Thin-leaved stringybark")[http://farrer.riv.csu.edu.au/ASGAP/eucal1a.html]
  
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Several other species, especially from the high plateau and mountains of central [[Tasmania]] such as ''E. coccifera'', ''E. subcrenulata'', and ''E. gunnii'' have produced extreme cold hardy forms and it is seed procured from these [[genetics|genetic]]ally hardy strains that are planted for ornament in colder parts of the world.
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Today, specimens of the Australian Mountain Ash, ''E. regnans'', are among the tallest trees in the world at up to 92 meters in height (Hickey, Kostoglou and Sargison 2005) and the tallest of all [[flowering plant]]s; other taller trees such as the Coast [[Redwood]] are all [[conifer]]s. There is credible evidence, however, that at the time of European settlement of Australia some Mountain Ash were perhaps the tallest plants in the world.
  
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The coolibah trees, referred to in [[Waltzing Matilda]], are eucalypts ''[[Eucalyptus coolabah|E. coolabah]]'' and ''[[Eucalyptus microtheca|E. microtheca]]''.
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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 ''E. pauciflora'' which is capable of withstanding cold and frost down to about –20 °C. Two sub-species, ''E. pauciflora niphophila'' and ''E. pauciflora debeuzevillei'', in particular are even hardier and can tolerate even quite severe continental type winters.
  
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==Animal relationships==
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Several other species, especially from the high plateau and mountains of central [[Tasmania]], such as ''E. coccifera'', ''E. subcrenulata'', and ''E. gunnii'', have produced extreme cold hardy forms and it is seed procured from these [[genetics|genetic]]ally hardy strains that are planted for ornament in colder parts of the world.
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An [[essential oil]] extracted from eucalypt 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.
 
  
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Eucalypts support the [[larva]]e of a number of [[Lepidoptera]] species - see [[list of Lepidoptera which feed on Eucalyptus]].
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The coolibah trees, referred to in the song "Waltzing Matilda," are eucalypts ''E. coolabah'' and ''E. microtheca''.
  
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==Hazards==
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==Animal Relationships==
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Eucalypts 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 deaths were actually caused by simply camping under them, as they shed whole and very large branches to conserve water during periods of drought. For this reason, one should ''never'' camp under an overhanging branch. This may be the real reason behind the [[drop bear]] story told to children - the idea is to keep them away from under dangerous branches.
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[[Image:Koala-ag1.jpg|thumb|right|280px|[[Koala]] eating leaves]]
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Eucalypts provide food for a large number of animals including [[koala]]s, [[cockatoo]]s, and many [[insect]]s. Many others live in the Eucalyptus forests. It has been estimated that 20 percent of Australia's [[mammal]]s are arboreal, living in trees.
  
 
==Fire==
 
==Fire==
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On warm days vapourised eucalyptus oil rises above the [[bush]] to create the characteristic distant blue haze of the Australian landscape. Eucalyptus oil is highly flammable (trees have been known to explode) 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]], both from reserve buds under the bark, and from fire-germinated seeds sprouting in the ashes.
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On warm days, vaporized Eucalyptus oil rises above the bush to create the characteristic distant blue haze of the Australian landscape. Eucalyptus oil is highly flammable (trees have been known to explode) and bush fires 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, both from reserve buds under the bark, and from fire-germinated seeds sprouting in the ashes.
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==Eucalyptus and Humans==
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The Indigenous Australians used, and still use, Eucalyptus for many purposes. The wood was used to make tools and for firewood, the bark for boats, and the leaves to make poison to harvest [[fish]] in a waterhole. The leaves and roots were also used as [[medicine]] for many ailments.
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In modern Australia, eucalypts are an important source of timber and their wood is used for construction, furniture making, pulpwood, and firewood. They also serve as windbreaks and ornamental trees and their flowers are a source of [[honey]]. Eucalyptus oil is extracted from the leaves and is used as an aroma and a medicinal ingredient, for instance in cough drops. Eucalyptus leaves are also used for decoration in floral arrangements.
  
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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.
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[[Image:Eucalyptus02.jpg|thumb|200px|A Eucalyptus tree]]
  
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<!-- delete these two?? —>
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===Hazards===
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Eucalypts regenerate quickly after [[fire]]. After the 2003 [[Canberra]] fires, hectares of imported species were killed, but in a matter of weeks the gum trees were putting out suckers and looking generally healthy.  
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Eucalypts 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 deaths were actually caused by simply camping under them, as they shed whole and very large branches to conserve water during periods of drought. For this reason, one should ''never'' camp under an overhanging branch.  
  
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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 fire that has had little impact on forests around Canberra has resulted in thousands of hectares of dead ash forests.  There has been some debate as to whether to leave the stands, or attempt to harvest the mostly undamaged timber.
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==Origin==
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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). However, 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 fifty thousand years ago, fires became much more frequent and the fire-loving eucalypts soon came to account for roughly 70 percent of Australian forest.
  
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Gum trees are also very accomplished at scavenging water at the expense of other plants.
 
  
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==Cultivation and uses==
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==Beyond Australia==
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Eucalypts have many uses which have made them [[economically]] important trees. Due to their fast growth the foremost of these 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.
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===California===
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In the 1850s, many Australians traveled to [[California]] in the [[United States]] to take part in the Gold Rush. Much of California has similar climate to parts of Australia and some people thought it would be a good idea to introduce Eucalyptus to the state. By the early 1900s, thousands of acres of Eucalyptus were planted with the encouragement of the state government and some city governments. It was hoped that they would provide a renewable source of timber for construction and furniture making. However this did not happen as they proved unsuitable for the task, 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.[http://wwwlibrary.csustan.edu/bsantos/euctoc.htm]
  
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The roots absorb lots of water and so eucalypts have been planted (or re-planted) 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=The Eucalyptus of California | publisher=Alley-Cass Publications | accessdate=2005-01-27}}</ref>. Drainage removes swamps which provide a habitat for [[mosquito]] [[larvae]].
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One way in which the eucalypts, 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.
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[[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.
 
  
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The [[nectar (plant)|nectar]] of some eucalypts produces high quality [[honey]]. Perhaps the [[Karri]] and the [[Yellow box]] are the best known.
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Eucalyptus forests in California have been criticized because they drive out the native plants and do not support native animals. Wetlands are also reduced as the fast growing plants use a lot of water (Henter 2005). Fire is also a problem. The 1991 Oakland Hills fire, which destroyed almost three thousand homes and killed 25 people, was largely caused, or at least made worse, by large numbers of eucalypts which were growing among the houses in the area. [http://magazine.audubon.org/incite/incite0201.html] Williams (2002) reports that Blue gum eucalyptus are called "gasoline trees" by firefighters, stating "Blue gum eucalyptus doesn't just burn, it explodes, sending firebrands and seeds shooting hundreds of feet in all directions. Living next to one of these trees is like living next to a fireworks factory staffed by chain-smokers." He further observed that introduced eucalyptus trees blocked drains, tore up pavement, and damaged foundations.
  
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The ghost gum's leaves were used by [[Indigenous Australians|Aborigines]] to catch fish. Soaking the leaves in water releases a mild tranquiliser which stuns fish temporarily.
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In some parts of California, Eucalyptus forests are being cut down and native trees and plants restored. "Eco-terrorists" have also destroyed some trees and are suspected of introducing insect pests from Australia that attack the trees.[http://alumni.ucsd.edu/magazine/vol2no1/features/wars.htm]
  
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==Plantation and ecological problems==
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===World-wide Cultivation===
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Eucalypts were 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]], [[Morocco]], [[Portugal]], [[South Africa]], [[Israel]] and [[Galicia (Spain)|Galicia]]. Several species have become [[invasive species|invasive]] and are causing major problems for local ecologies. In [[Spain]], they have been planted in pulpwood [[plantation]]s, replacing native [[oak]] woodland. As in other such areas, while the original woodland supports numerous species of native animal life (insects, birds, salamanders, etc.), the eucalypt groves are inhospitable to the local wildlife which is not adapted to them, leading to silent forests and the decline of wildlife populations. On the other hand, eucalypts are the basis for several industries, such as sawmilling, pulp, charcoal and others.
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[[Image:Eucalyptus forest2.jpg|thumb|300px|Eucalyptus forest]]
  
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Eucalypts have been imported into California, primarily for use in windbreaks enclosing large tracts of arid western San Joaquin valley farmland. While some of the Australian gumwoods make beautiful furniture wood, resembling [[Teak]], an inappropriate type for this purpose was imported into California. This type is neither attractive as a veneer (its color varies from yellowish-gray to grayish-green), useful as lumber (it tends to warp and split after cutting), or even thought well of as firewood (oak, nutwoods and fruitwoods are the preferred commercial firewoods in Northern California).
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Eucalypts have been planted in some places around the world to dry up swamps, which happens because of their great consumption of [[water]]. This has helped to control [[malaria]] because it takes away the breeding places for the [[mosquito]]es that carry the disease. At one time, it was thought that the smell of the trees was what brought the health-giving effects.
  
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Their presence in the [[Oakland, California|Oakland]]-[[Berkeley, California|Berkeley]] hills in California has led to periodic wildfires that have spread into dense urban areas, and since these rapidly regenerate from root sprouts the problem will continue until they are completely removed. Severe cold for a period of several weeks has killed off large stands, which had to be immediately removed to eliminate the consequent severe fire hazard. The shedding of bark creates an open and flammable forest litter that also snags on limbs and so provides a direct fire path from forest floor to tree crown. In some ecologicaly sensitive areas such as [[Angel Island, California|Angel Island]] in [[San Francisco Bay]], an eradication program is underway to completely restore the original oak-studded grasslands.
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Eucalypts are being grown on plantations in many parts of the world, including the [[United States]], [[Brazil]], [[Morocco]], [[Portugal]], [[South Africa]], [[Israel]], and [[Spain]]. Pulpwood for papermaking and Eucalyptus oil are the two most important Eucalyptus products today. The burning of Eucalyptus wood for energy is considered to hold great potential as a renewable energy source.[http://www.hort.purdue.edu/newcrop/duke_energy/Eucalyptus.html]
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As in California, some Eucalyptus plantations in these nations have been criticized because they replace native vegetation and traditional land uses.
  
 
==References==
 
==References==
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<references />
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* Henter, H. 2005. [http://alumni.ucsd.edu/magazine/vol2no1/features/wars.htm Tree Wars: The Secret Life of Eucalyptus]. ''UCSD Alumni'' 2(1) (January , 2005, accessed July 12, 2006).
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* Hickey, J. E., P. Kostoglou, and G. J. Sergison. 2005. Tasmania's Tallest Trees]. Forestry Tasmania.
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* Santos, R. 1997. [http://www.library.csustan.edu/bsantos/euctoc.htm The Eucalyptus of Califonia: Seeds of Good or Seeds of Evil?]. Denair, CA:Alley-Cass Publications.
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* Williams, T. 2002. [http://magazine.audubon.org/incite/incite0201.html America's Largest Weed]. ''Audubon'' (January 2002, accessed July 12, 2006).
  
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==See also==
 
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{{Commons|Eucalyptus}}
 
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* ''[[Angophora]]''
 
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* ''[[Corymbia]]''
 
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==External links==
 
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* [http://www.anbg.gov.au/cpbr/cd-keys/Euclid/sample/html/index.htm EUCLID Sample], CSIRO
 
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* [http://farrer.riv.csu.edu.au/ASGAP/eucalypt.html The Eucalyptus Page]
 
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* [http://plantnet.rbgsyd.nsw.gov.au/PlantNet/Euc/ EucaLink]
 
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* [http://www.angelfire.com/bc/eucalyptus/ The Hardy Eucalyptus Page]
 
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*[http://www.cirrusimage.com/tree_Eucalyptus.htm ''Eucalyptus globulus''] Diagnostic photos: tree, leaves, bark
 
  
 
==Photo gallery==
 
==Photo gallery==
 
<gallery>
 
<gallery>
  
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<!-- 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 not encyclopaedic to say merely "eucalyptus"—>
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<!-- 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 not encyclopaedic to say merely "eucalyptus"—>
  
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Image:Eucalyptus forest.jpg|Eucalyptus forest in [[East Gippsland Shire|East Gippsland]], [[Victoria (Australia)|Victoria]].  Mostly ''Eucalyptus albens'' (white box).
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Image:Eucalyptus forest3.jpg|Eucalyptus forest in East Gippsland, Victoria (Australia). Mostly ''Eucalyptus albens'' (white box).
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Image:Eucalyptus forest3.jpg|Eucalyptus forest in [[East Gippsland Shire|East Gippsland]], [[Victoria (Australia)|Victoria]]. Mostly ''Eucalyptus albens'' (white box).
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Image:Eucalypt forest.jpg|Eucalyptus forest in East Gippsland, Victoria (Australia). Mostly ''Eucalyptus albens'' (white box).
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Image:Eucalypt forest.jpg|Eucalyptus forest in [[East Gippsland Shire|East Gippsland]], [[Victoria (Australia)|Victoria]]. Mostly ''Eucalyptus albens'' (white box).
 
 
Image:Log embedded in white box.jpg|A log embedded in a ''Eucalyptus albens'' (white box) tree.
 
Image:Log embedded in white box.jpg|A log embedded in a ''Eucalyptus albens'' (white box) tree.
 
Image:Eucalyptustreewithsun.JPG|A eucalyptus tree with the sun shining through its branches.
 
Image:Eucalyptustreewithsun.JPG|A eucalyptus tree with the sun shining through its branches.
 
Image:Eucalyptus tree.jpg|Eucalyptus
 
Image:Eucalyptus tree.jpg|Eucalyptus
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Image:Applebox.JPG|''Eucalyptus bridgesiana'' (Apple box) on [[Red Hill, Australian Capital Territory]].
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Image:Applebox.JPG|''Eucalyptus bridgesiana'' (Apple box) on Red Hill, Australian Capital Territory.
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image:euc.uk.600pix.jpg|''Eucalyptus gunnii'' planted in southern [[England]]. The lower part of the trunk is covered in [[ivy]].
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image:euc.uk.600pix.jpg|''Eucalyptus gunnii'' planted in southern [[England]]. The lower part of the trunk is covered in ivy.
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Image:Gumnut tree.jpg|Corymbia tree, growing in [[Melbourne]], [[Australia]]
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Image:Gumnut tree.jpg|Corymbia tree, growing in Melbourne, [[Australia]]
 
Image:Eucalyptus cinera x pulverulenta.jpg|Cinera x Pulverulenta - National Botanical Gardens Canberra
 
Image:Eucalyptus cinera x pulverulenta.jpg|Cinera x Pulverulenta - National Botanical Gardens Canberra
 
Image:Eucalyptus wildfire seeds.jpg|Eucalyptus wildfire seeds
 
Image:Eucalyptus wildfire seeds.jpg|Eucalyptus wildfire seeds
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Image:Eucalyptus leucoxylon1.jpg|''Eucalyptus leuxoxylon'' 'Rosea'
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Image:Eucalyptus gall.jpg|Eucalyptus gall 'Rosea'
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</gallery>
 
</gallery>
  
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{{Link FA|he}}
 
 
{{credit|59625484}}
 
{{credit|59625484}}
 
[[Category:Life sciences]]
 
[[Category:Life sciences]]
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[[Category:Plants]]

Latest revision as of 12:22, 21 January 2023

Eucalyptus
Eucalyptus flowers2.jpg
Eucalyptus melliodora foliage and flowers
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Myrtales
Family: Myrtaceae
Genus: Eucalyptus
Charles Louis L'Héritier de Brutelle
Species

About eight hundred

Eucalyptus is a diverse genus of trees (rarely shrubs), the members of which dominate the tree flora of Australia. There are more than eight hundred species of Eucalyptus, mostly native to Australia, with a very small number of native species found in parts of adjacent New Guinea and Indonesia and one as far away as the Philippines. The Eucalyptus genus is part of the Myrtle family (Myrtaceae), which is a family of dicotyledon plants—flowering plants whose seed typically contains two embryonic leaves or cotyledons.

Eucalypts, as they are also called, can be found in almost every part of the Australian continent, adapted to all of Australia's climatic conditions; in fact, no other continent is so characterized by a single genus of tree as Australia is by Eucalyptus.

On the other hand, the deliberate introduction of eucalyptus to other parts of the world, as invasive species, has sometimes resulted in unintended consequences, including deadly wildfires, reduced habitat for native plants and animals, and reduction of valuable wetlands. They serve as a reminder that nature involves many complex interactions, formed over millions of years, and human interventions must not be pursued lightly.

Description

Eucalyptus leuxoxylon

The most readily recognizable characteristics of Eucalyptus species are the distinctive flowers and fruits. The name Eucalyptus means "well-covered"; it describes the bud cap (technically called an operculum). This cap forms from modified petals and falls off as the flower opens. Thus flowers have no petals, decorating themselves instead with many showy stamens. The woody fruits are roughly cone-shaped and have valves at the end that open to release the seeds.

A small genus of similar trees, Angophora, has also been known since the eighteenth century. In 1995, new evidence, largely genetic, indicated that some prominent eucalypt species were actually more closely related to Angophora than to 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."

Nearly all eucalypts are evergreen, but some tropical species lose their leaves at the end of the dry season. As in other members of the Myrtle family, eucalypt leaves are covered with oil glands. The copious oils produced are an important feature of the genus. Eucalypts also exhibit leaf dimorphism. When young, their leaves are opposite, oval to roundish, and occasionally without a petiole. When one to a few years old, the leaves become alternate, lanceolate to falcate (sickle-shaped), quite slender, and pendulous with longer petioles. The adult leaves of most species, as well as the juvenile leaves of some, are the same on both sides, lacking the distinction between upper and lower surfaces shown by the leaves of most plants. Most species do not flower until adult foliage starts to appear; E. cinerea and E. perriniana are notable exceptions.

Eucalyptus species have various types of bark. In smooth-barked trees, most of the bark is shed, leaving a smooth surface that is often colorfully mottled. With rough-barked trees the dead bark persists on the tree and dries out. Many trees, however, have smooth bark at the top but rough bark on the trunk or its bottom.

A eucalyptus tree
The thick, protective bark of Eucalyptus quadrangulata

Many eucalypts are called "gum trees" because of a sticky, gum-like substance they exude from their trunks. Some of the other common names for different eucalypts include:

  • Apple - They look like apple trees (eg. Angophora bakeri, "Narrow-leaved apple")
  • Ash - Their timber is similar to that of European ash trees (eg. E. regnans, "Mountain ash")
  • Blackbutt - The lower bark is usually black due to past fires (eg. E. pilularis, "Blackbutt")
  • Bloodwood - Timber often has pockets of a dark red gum called "kino" (eg. Corymbia eximia, "Yellow bloodwood")
  • Box - The bark stays on the tree and is short fibered; plates of bark may shear off with age (eg. E. melliodora ("Yellow box")
  • Ironbark - The bark stays on the tree and is hard and deeply furrowed (eg. E. crebra, "Narrow-leaved ironbark")
  • Mallee - Multi-stemmed trees, usually fairly short (eg. E. albida, "White-leaved mallee")
  • Peppermint - The oil in the leaves smells like peppermint. (eg. E. dives, "Broad-leaved peppermint")
  • Ribbon Gum - Bark is deciduous and is shed in long strips that hang from the branches (eg. E. viminalis, "Ribbon gum")
  • Scribbly Gum - The smooth trunk is marked with "scribbles" caused by an insect larva (eg. E. sclerophylla, "Scribbly gum")
  • Stringybark - Bark consists of long fibers that can be pulled off in "strings" (eg. E. eugenioides, "Thin-leaved stringybark")[1]

Today, specimens of the Australian Mountain Ash, E. regnans, are among the tallest trees in the world at up to 92 meters in height (Hickey, Kostoglou and Sargison 2005) and the tallest of all flowering plants; other taller trees such as the Coast Redwood are all conifers. There is credible evidence, however, that at the time of European settlement of Australia some Mountain Ash were perhaps the tallest plants in the world.

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 E. pauciflora which is capable of withstanding cold and frost down to about –20 °C. Two sub-species, E. pauciflora niphophila and E. pauciflora debeuzevillei, in particular are even hardier and can tolerate even quite severe continental type winters.

Several other species, especially from the high plateau and mountains of central Tasmania, such as E. coccifera, E. subcrenulata, and E. gunnii, have produced extreme cold hardy forms and it is seed procured from these genetically hardy strains that are planted for ornament in colder parts of the world.

The coolibah trees, referred to in the song "Waltzing Matilda," are eucalypts E. coolabah and E. microtheca.

Animal Relationships

Koala eating leaves

Eucalypts provide food for a large number of animals including koalas, cockatoos, and many insects. Many others live in the Eucalyptus forests. It has been estimated that 20 percent of Australia's mammals are arboreal, living in trees.

Fire

On warm days, vaporized Eucalyptus oil rises above the bush to create the characteristic distant blue haze of the Australian landscape. Eucalyptus oil is highly flammable (trees have been known to explode) and bush fires 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, both from reserve buds under the bark, and from fire-germinated seeds sprouting in the ashes.

Eucalyptus and Humans

The Indigenous Australians used, and still use, Eucalyptus for many purposes. The wood was used to make tools and for firewood, the bark for boats, and the leaves to make poison to harvest fish in a waterhole. The leaves and roots were also used as medicine for many ailments.

In modern Australia, eucalypts are an important source of timber and their wood is used for construction, furniture making, pulpwood, and firewood. They also serve as windbreaks and ornamental trees and their flowers are a source of honey. Eucalyptus oil is extracted from the leaves and is used as an aroma and a medicinal ingredient, for instance in cough drops. Eucalyptus leaves are also used for decoration in floral arrangements.

A Eucalyptus tree

Hazards

Eucalypts 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 deaths were actually caused by simply camping under them, as they shed whole and very large branches to conserve water during periods of drought. For this reason, one should never camp under an overhanging branch.

Origin

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). However, 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 fifty thousand years ago, fires became much more frequent and the fire-loving eucalypts soon came to account for roughly 70 percent of Australian forest.


Beyond Australia

California

In the 1850s, many Australians traveled to California in the United States to take part in the Gold Rush. Much of California has similar climate to parts of Australia and some people thought it would be a good idea to introduce Eucalyptus to the state. By the early 1900s, thousands of acres of Eucalyptus were planted with the encouragement of the state government and some city governments. It was hoped that they would provide a renewable source of timber for construction and furniture making. However this did not happen as they proved unsuitable for the task, 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.[2]

One way in which the eucalypts, 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 drive out the native plants and do not support native animals. Wetlands are also reduced as the fast growing plants use a lot of water (Henter 2005). Fire is also a problem. The 1991 Oakland Hills fire, which destroyed almost three thousand homes and killed 25 people, was largely caused, or at least made worse, by large numbers of eucalypts which were growing among the houses in the area. [3] Williams (2002) reports that Blue gum eucalyptus are called "gasoline trees" by firefighters, stating "Blue gum eucalyptus doesn't just burn, it explodes, sending firebrands and seeds shooting hundreds of feet in all directions. Living next to one of these trees is like living next to a fireworks factory staffed by chain-smokers." He further observed that introduced eucalyptus trees blocked drains, tore up pavement, and damaged foundations.

In some parts of California, Eucalyptus forests are being cut down and native trees and plants restored. "Eco-terrorists" have also destroyed some trees and are suspected of introducing insect pests from Australia that attack the trees.[4]

World-wide Cultivation

Eucalyptus forest

Eucalypts have been planted in some places around the world to dry up swamps, which happens because of their great consumption of water. This has helped to control malaria because it takes away the breeding places for the mosquitoes that carry the disease. At one time, it was thought that the smell of the trees was what brought the health-giving effects.

Eucalypts are being grown on plantations in many parts of the world, including the United States, Brazil, Morocco, Portugal, South Africa, Israel, and Spain. Pulpwood for papermaking and Eucalyptus oil are the two most important Eucalyptus products today. The burning of Eucalyptus wood for energy is considered to hold great potential as a renewable energy source.[5]

As in California, some Eucalyptus plantations in these nations have been criticized because they replace native vegetation and traditional land uses.

References
ISBN links support NWE through referral fees


Photo gallery

  • Eucalyptus forest in East Gippsland, Victoria (Australia). Mostly Eucalyptus albens (white box).

  • Eucalyptus forest in East Gippsland, Victoria (Australia). Mostly Eucalyptus albens (white box).

  • A log embedded in a Eucalyptus albens (white box) tree.

  • A eucalyptus tree with the sun shining through its branches.

  • Eucalyptus

  • Eucalyptus bridgesiana (Apple box) on Red Hill, Australian Capital Territory.

  • Eucalyptus gunnii planted in southern England. The lower part of the trunk is covered in ivy.

  • Corymbia tree, growing in Melbourne, Australia

  • Cinera x Pulverulenta - National Botanical Gardens Canberra

  • Eucalyptus wildfire seeds

  • Eucalyptus gall 'Rosea'

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