''Corymbia citriodora'', commonly known as lemon-scented gum and other common names, is a species of tall tree that is

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

to north-eastern Australia. It has smooth white to pink bark, narrow lance-shaped to curved adult leaves, flower buds in groups of three, white flowers and urn-shaped or barrel-shaped fruit.

Description

''Corymbia citriodora'' is a tree that typically grows to a height of , sometimes to and forms a

lignotuber A lignotuber is a woody swelling of the root crown possessed by some plants as a protection against destruction of the plant stem, such as by fire. Other woody plants may develop basal burls as a similar survival strategy, often as a response ...

. It has smooth, pale, uniform or slightly mottled, white to pink or coppery bark that is shed in thin flakes. Young plants and

coppice Coppicing is a traditional method of woodland management which exploits the capacity of many species of trees to put out new shoots from their stump or roots if cut down. In a coppiced wood, which is called a copse, young tree stems are repeate ...

regrowth have egg-shaped to lance-shaped leaves that are long and wide. Adult leaves are the same shade of glossy green on both sides, often lemon-scented when crushed, narrow lance-shaped to curved, long and wide tapering to a petiole long. The flower buds are borne in leaf axils on a branched peduncle long, each branch with three buds on

pedicels In botany, a pedicel is a stem that attaches a single flower to the inflorescence. Such inflorescences are described as ''pedicellate''. Description Pedicel refers to a structure connecting a single flower to its inflorescence. In the absenc ...

long. Mature buds are oval to pear-shaped, long and wide with a rounded, conical or slightly beaked operculum. Flowering occurs in most months and the flowers are white. The fruit is a woody urn-shaped or barrel-shaped capsule long and wide with the valves enclosed in the fruit.

Taxonomy and naming

Lemon-scented gum was first formally described in 1848 by

William Jackson Hooker Sir William Jackson Hooker (6 July 178512 August 1865) was an English botanist and botanical illustrator, who became the first director of Kew when in 1841 it was recommended to be placed under state ownership as a botanic garden. At Kew he ...

who gave it the name ''Eucalyptus citriodora'' in Thomas Mitchell's ''Journal of an Expedition into the Interior of Tropical Australia''. In 1995 Ken Hill and Lawrie Johnson changed the name from ''Eucalyptus citriodora'' to ''Corymbia citriodora''. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

(''citriodora'') is

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

, meaning "lemon-scented". Lemon-scented gum is also commonly known as citron scented gum, citron-scented gum, lemon gum, lemon scented gum, lemonscented gum, spotted gum and lemon eucalyptus. ''Corymbia citriodora'' is similar to '' C. maculata'' and '' C. henryi''.

Distribution and habitat

''Corymbia citriodora'' grows in undulating country in open forest and woodland in several disjunct areas in Queensland and as far south as

Coffs Harbour Coffs Harbour is a city on the Mid North Coast of New South Wales, Australia, north of Sydney, and south of Brisbane. It is one of the largest urban centres on the North Coast, with a population of 78,759 as per 2021 census. The Gumbaynggirr ...

in New South Wales. In Queensland it is found as far north as Lakeland Downs and

Cooktown Cooktown is a coastal town and locality in the Shire of Cook, Queensland, Australia. Cooktown is at the mouth of the Endeavour River, on Cape York Peninsula in Far North Queensland where James Cook beached his ship, the Endeavour, for rep ...

and as far inland as Hughenden and Chinchilla. Kings Park in

Perth Perth is the capital and largest city of the Australian state of Western Australia. It is the fourth most populous city in Australia and Oceania, with a population of 2.1 million (80% of the state) living in Greater Perth in 2020. Perth is ...

has an avenue of this species planted many years ago, but the species has spread to become an environmental

weed A weed is a plant considered undesirable in a particular situation, "a plant in the wrong place", or a plant growing where it is not wanted.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. ...

in the Sydney and Blue Mountains in New South Wales and in open woodland areas in the south-west of Western Australia. Some naturalists and conservationists do not recognise the genus ''

Corymbia ''Corymbia'', commonly known as bloodwoods, is a genus of about one hundred species of tree that, along with ''Eucalyptus'', ''Angophora'' and several smaller groups, are referred to as eucalypts. Until 1990, corymbias were included in the gen ...

'' and still categorise its species within ''

Eucalyptus ''Eucalyptus'' () is a genus of over seven hundred species of flowering trees, shrubs or mallees in the myrtle family, Myrtaceae. Along with several other genera in the tribe Eucalypteae, including ''Corymbia'', they are commonly known as eucal ...

''.

Essential oil

The

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

of the lemon-scented gum mainly consists of

citronellal Citronellal or rhodinal ( C10 H18 O) is a monoterpenoid aldehyde, the main component in the mixture of terpenoid chemical compounds that give citronella oil its distinctive lemon scent. Citronellal is a main isolate in distilled oils from the p ...

(80%), produced largely in Brazil and China. Unrefined oil from the lemon eucalyptus tree is used in

perfumery Perfume (, ; french: parfum) is a mixture of fragrant essential oils or aroma compounds (fragrances), fixatives and solvents, usually in liquid form, used to give the human body, animals, food, objects, and living-spaces an agreeable scent. Th ...

, and a refined form of this oil is used in

insect repellent An insect repellent (also commonly called "bug spray") is a substance applied to skin, clothing, or other surfaces to discourage insects (and arthropods in general) from landing or climbing on that surface. Insect repellents help prevent and cont ...

s, especially against

mosquitoes Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "lit ...

. The refined oil's citronellal content is turned into cis- and trans- isomers of p-menthane-3,8-diol (PMD), a process which occurs naturally as the eucalyptus leaves age. This refined oil, which includes related compounds from the essential corymbia citriodora, is known widely by its registered tradename, "Citrepel" or "Citriodiol", but also by generic names which vary by region: "oil of lemon eucalyptus" or "OLE" (USA); "PMD rich botanic oil" or "PMDRBO" (Europe); "PMD and related oil of lemon eucalyptus compounds" (Canada); Extract of Lemon Eucalyptus (Australia). Pure PMD is synthesized for commercial production from synthetic citronellal. Essential oil refined from the leaves of the tree can contain up to 98% citronella content. The smell of the essential oil can vary, but mostly includes a strong odor comparable alone to citronella oil, with a slight hint of lemon scent. A study comparing mosquito repellents found that products using the oil of lemon eucalyptus were effective at driving mosquitos away from a human hand.Stacy D. Rodriguez; Lisa L. Drake; David P. Price; John I. Hammond; Immo A. Hansen. 2015
The Efficacy of Some Commercially Available Insect Repellents for ''Aedes aegypti'' (Diptera: Culicidae) and ''Aedes albopictus'' (Diptera: Culicidae)
''Journal of Insect Science'' 15 (1): 140. DOI: https://doi.org/10.1093/jisesa/iev125 File:Lemon-scented gum - trunk bark.jpg, Bark File:Corymbia citriodora - shedding bark 2.jpg, Shedding trunk bark File:Corymbia citriodora - shedding bark 1.jpg, Shedding trunk bark File:Corymbia citriodora - juvenile leaves.jpg, Juvenile leaves File:Lemon-scented gum - leaves.jpg, Adult leaves File:Corymbia citriodora - shedding bark 5.jpg, Fruit

References

External links