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

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

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 In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branch ...

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 botany, botanist and botanical illustrator, who became the first director of Kew Gardens, Kew when in 1841 it was recommended to be placed under state ownership as a botan ...

, 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 (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

(''citriodora'') is

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

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

'' and still categorise its species within ''

Eucalyptus ''Eucalyptus'' () is a genus of more than 700 species of flowering plants in the family Myrtaceae. Most species of ''Eucalyptus'' are trees, often Mallee (habit), mallees, and a few are shrubs. Along with several other genera in the tribe Eucalyp ...

''.

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, locally nicknamed Coffs, is a coastal 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 a ...

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

Chinchilla Chinchilla refers to either of two species ('' Chinchilla chinchilla'' and '' Chinchilla lanigera'') of crepuscular rodents of the parvorder Caviomorpha, and are native to the Andes mountains in South America. They live in colonies called "her ...

. Kings Park in

Perth Perth () is the list of Australian capital cities, capital city of Western Australia. It is the list of cities in Australia by population, fourth-most-populous city in Australia, with a population of over 2.3 million within Greater Perth . The ...

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, growing where it conflicts with human preferences, needs, or goals.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. Pla ...

in the Sydney and Blue Mountains region in New South Wales and in open woodland areas in the south-west of Western Australia.

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 ...

of the lemon-scented gum mainly consists of citronellal (80%), produced largely in Brazil and China. Unrefined oil from the lemon eucalyptus tree is used in perfumery, and a refined form of this oil is used in

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

s, especially against

mosquitoes Mosquitoes, the Culicidae, are a family of small flies consisting of 3,600 species. The word ''mosquito'' (formed by '' mosca'' and diminutive ''-ito'') is Spanish and Portuguese for ''little fly''. Mosquitoes have a slender segmented body, ...

. The refined oil's citronellal content is turned into cis- and trans- isomers of

p-menthane-3,8-diol ''p''-Menthane-3,8-diol, also known as ''para''-menthane-3,8-diol, PMD, or menthoglycol, is an organic compound classified as a diol and a terpenoid. It is colorless. Its name reflects the hydrocarbon backbone, which is that of ''p''-menthane ...

(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