Lemon-Scented Gum, blue spotted gum, lemon eucalyptus, eucalyptus citriodora.
Corymbia citriodora

Family: Myrtaceae

What it is like

Lemon-scented gum or Corymbia citriodora is a medium to large evergreen tree with smooth powdery bark that is pale grey, cream or pink in colour. It is widely cultivated in Australia for its timber and essential oil and is often grown as an ornamental tree. Its leaves are used as a herbal remedy. It yields essential oil used against coughs and colds, sore throats, cuts, skin infections, blocked nasal passages, etc. However, it should not be consumed in high amounts to avoid toxic effects on the body. Aside from the medicinal uses, the oil is also used in perfumery especially that this species has high citronella content. It is also used as an insect repellent. The tree sources an oleo-resin which contains tannins used in the treatment of diarrhoea, bladder inflammation, and cuts. The plant produces a sweet manna-like substance that is scraped off the leaves and eaten. The wood is hard and durable, and used in general and heavy constructions and for fuel. C. citriodora is endemic to temperate and tropical eastern Australia. Extensively planted as an ornamental tree in many regions of the world, and has been planted for commercial purposes in South America (mainly in Brazil), China, India, Sri Lanka, Central America, the West Indies, and most countries in southern Africa. In South-East Asia it is mainly planted in Peninsular Malaysia, Thailand, and Vietnam. Also known as: Lemon-scented gum, citron-scent gum; Lemon gum tree. Spanish: eucalipto. French: Eucalyptus a odeur de citron. Australia: lemon-scented iron gum; spotted gum; spotted iron gum. Germany: Zitronen- Eukalyptus. Italy: Eucalipto a profumo di limone. Puerto Rico: eucalipto de lim?n; eucalipto de pantano; eucalipto oloroso.

Corymbia citriodora is an evergreen Tree growing to 45 m (147ft) by 30 m (98ft) at a fast rate. See above for USDA hardiness. It is hardy to UK zone 10. The flowers are pollinated by Bees. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It cannot grow in the shade. It prefers moist soil and can tolerate drought.

Height (m): 45

Where it is found

Usually found in heavy soils, but also succeeding on deep sandy loams in coastal regions.

Australia - Queensland, New South Wales.

Conservation Status: This taxon has not yet been assessed

Countries/locations it is found in

C. citriodora is endemic to temperate and tropical eastern Australia. Extensively planted as an ornamental tree in many regions of the world, and has been planted for commercial purposes in South America (mainly in Brazil), China, India, Sri Lanka, Central America, the West-Indies, and most countries in southern Africa. In South-East Asia it is mainly planted in Peninsular Malaysia, Thailand, and Vietnam.

How it is used

Food

Rating: 2

Produces a sweet manna-like substance that is scraped off the leaves and eaten. Honey/honey flora plant. Spice and culinary herb.

Manna: this is a sweet substance that exudes naturally from certain plants, usually from the stems.

Medicine

Rating: 3

Eucalyptus leaves are a traditional Aboriginal herbal remedy. The essential oil found in the leaves is a powerful antiseptic and is used all over the world for relieving coughs and colds, sore throats and other infections. The essential oil is a common ingredient in many over-the-counter cold remedies. An essential oil obtained from the leaves is antibacterial. The essential oil obtained from various species of eucalyptus is a very powerful antiseptic, especially when it is old, because ozone is formed in it on exposure to air. It has a decided disinfectant action, destroying the lower forms of life. The oil can be used externally, applied to cuts, skin infections etc, it can also be inhaled for treating blocked nasal passages, it can be gargled for sore throat and can also be taken internally for a wide range of complaints. Some caution is advised, however, because like all essential oils, it can have a deleterious effect on the body in larger doses. An oleo-resin is exuded from the tree. It can also be obtained from the tree by making incisions in the trunk. This resin contains tannin and is powerfully astringent, it is used internally in the treatment of diarrhoea and bladder inflammation, externally it is applied to cuts etc.

Antibacterial: Kills bacteria.

Antidiarrhoeal: Provides symptomatic relief for diarrhoea. Also see Astringent.

Antiinflammatory: Reduces inflammation of joints, injuries etc.

Antiseptic: Preventing sepsis, decay or putrefaction, it destroys or arrests the growth of micro-organisms.

Antitussive: Prevents or relieves coughing.

Astringent: Produces contraction in living tissue, reducing the flow of secretions and discharges of blood, mucus, diarrhoea etc.

Disinfectant: Used for cleaning wounds.

Mouthwash: Treats problems such as mouth ulcers.

Skin: Plants used in miscellaneous treatments for the skin.

Other

Rating: 4

Fuels: Biofuels, Charcoal, Fuelwood. Environmental Uses: Ornamental, Amenity, Land reclamation, Revegetation, Shade and shelter, Windbreak. Other Uses: A lemon-scented essential oil is obtained from the leaves. It is used, especially in perfumery but also medicinally. The leaves yield between 0.5 to 2.0% essential oil. This species is a very rich source of citronella, which is much used in the perfumery industry. Some batches of the essential oil contain 98% citronella. Glabrous leaves may contain oil with 65.5% citronellal, 12.2% citronella, and 3.6% isopulegol; hairy leaves contain more oil with 86.6- 90.1% citronellal, 4.6 - 6.0% citronella, and 0.7 - 0.8% isopulegol, 1-pinene, b-pinene, and isovaleric aldehyde are also recovered. The leaves and the essential oil are used as an insect repellent. The leaves are also an ingredient of potpourri. The bark may contain up to 12% tannin. The heartwood is pale grey-brown to dark brown; it is demarcated from the up to 60mm wide band of white or cream sapwood. The grain is straight or interlocked and occasionally wavy; the texture open and coarse. The wood is hard, strong and tough. It saws easily, planes well, but is rather difficult to nail and prone to checking and collapsing during drying. The timber is susceptible to marine borer and termite attacks It is used for general and heavy construction such as frame and bridge construction, flooring, cladding, tool handles and case manufacturing. The wood is used for fuel. The hard heavy wood (sp. grav. 0.75 - 1.1) burns steadily and makes a good charcoal with an ash content of 1 - 2%. Environmental Ornamental, Amenity, Land reclamation, Revegetation, Shade and shelter, Windbreak.

Biomass: Provides a large quantity of plant material that can be converted into fuel etc.

Charcoal: Used for fuel, drawing, deodorant, filter, fertilizer etc.

Cosmetic: Used to improve the physical appearence of a person.

Disinfectant: Plants used for disinfecting.

Essential: Essential oils that are used in perfumery, medicines, paint solvents, insect repellents etc.

Fuel: Usually wood, plant materials that have been mentioned as being a good fuel.

Insecticide: Kills insects.

Pot-pourri: Aromatic plants used to impart a pleasant smell to an area. Can this be grouped with incense or essential oil?

Resin: Used in perfumery, medicines, paints, soap making etc. This also includes turpentine, which is extracted from many resins and used as a preservative, water proofer etc,

Shelterbelt: Wind resistant plants than can be grown to provide shelter in the garden etc.

Tannin: An astringent substance obtaied from plants, it is used medicinally, as a dye and mordant, stabilizer in pesticide etc.

Wood: A list of the trees and shrubs that are noted for having useful wood.

Attracts Wildlife: Plants noted for attracting wildlife

Food Forest: Plants for Edible Forest Gardens and Food Forests.

How it is grown

Succeeds in tropical and subtropical, arid to semiarid zones. The plant is said to grow best where the annual rainfall, falling mostly in the summer, is 600 to 1,300mm, with a 5 - 7 month dry season. Plants withstand high temperatures (29 - 35°c mean monthly maximum) and light frosts. Prefers a sunny position in a moderately fertile well-drained moisture retentive circum-neutral soil. Tolerates poor and dry soils, especially those low in mineral elements. Plants can be grown in infertile clays, laterites, poor and gravelly soils and podzols, preferably well drained. Established plants are drought tolerant. Does not succeed in frost hollows or in windy sites. A very fast growing species. Flowering usually starts within 2 years after planting and seeds are produced abundantly by 5 years of age. When grown for fuel, yields of 10 - 21 cubic metres per hectare per year have been obtained. Eucalyptus species have not adopted a deciduous habit and continue to grow until it is too cold for them to do so. This makes them more susceptible to damage from sudden cold snaps. If temperature fluctuations are more gradual, as in a woodland for example, the plants have the opportunity to stop growing and become dormant, thus making them more cold resistant. A deep mulch around the roots to prevent the soil from freezing also helps the trees to survive cold conditions. The members of this genus are remarkably adaptable however, there can be a dramatic increase in the hardiness of subsequent generations from the seed of survivors growing in temperate zones. Cultivated in warm temperate areas for its essential oil, it thrives in a Mediterranean climate. Eucalyptus monocultures are an environmental disaster, they are voracious, allelopathic and encourage the worst possible attitudes to land use and conservation. The trees cast a very light shade. Flower buds are formed in the summer prior to flowering and seed capsules need at least a further year in which to ripen. Plants are shallow-rooting and, especially in windy areas, should be planted out into their permanent positions when small to ensure that they do not suffer from wind-rock. They strongly resent root disturbance and should be container grown before planting out into their permanent position. The flowers are rich in nectar and are a good bee crop. The leaves are strongly lemon-scented when crushed.

Propagating it: Seed - surface sow in a seedtray in a sunny position and do not allow the compost to dry out. Species that come from high altitudes appreciate 6 - 8 weeks cold stratification at 2°c. Germination rates vary but usually average 30 - 50%. Rapid and complete germination is achieved under moist, warm conditions (25 - 30°c is optimal in the laboratory) in the presence of light. The seeds of this species are relatively large for a eucalypt and can be sown directly without pre-treatment into containers filled with a sterilized freely draining mixture of loam and sand and covered with a light sprinkling of fine sand. Pot up the seedlings into individual pots as soon as the second set of seed leaves has developed, if left longer than this they might not move well. Seedlings are planted out in the field when they reach a height of about 25 cm, 10 - 12 weeks after sowing. This should coincide with the onset of the rainy season in tropical countries. The seed has long viability.

Best place to grow:

Habit: Tree

Hardiness: 10-12

Growth: Fast

Soil: Light (sandy), medium, heavy (clay)

Shade: No shade

Moisture: Moist

Things to keep in mind

Citronellal, an essential oil found in most Eucalyptus species is reported to be mutagenic when used in isolation. In large doses, oil of eucalyptus, like so many essential oils has caused fatalities from intestinal irritation. Death is reported from ingestion of 4 - 24 ml of essential oils, but recoveries are also reported for the same amount. Symptoms include gastroenteric burning and irritation, nausea, vomiting, diarrhoea, oxygen deficiency, weakness, dizziness, stupor, difficult respiration, delirium, paralysis, convulsions, and death, usually due to respiratory failure.

Naturalized and invasive in disturbed areas and open forests. Once established, this species has the potential to out-compete native vegetation through the production of allelopathic substances which completely inhibit the germination, growth and establishment of native plants. C. corymbia may also reduce ground-water availability, modify soil nutrients and increase the risk of soil erosion. known to be invasive in Pakistan and Cuba.

Its other names

Local names

Lemon-scented gum or Corymbia citriodora. Also known as: Lemon-scented gum, citron-scent gum; Lemon gum tree. Spanish: eucalipto. French: Eucalyptus a odeur de citron. Australia: lemon-scented iron gum; spotted gum; spotted iron gum. Germany: Zitronen- Eukalyptus. Italy: Eucalipto a profumo di limone. Puerto Rico: eucalipto de lim—n; eucalipto de pantano; eucalipto oloroso.

Synonyms

Corymbia variegata (F.Muell.) K.D.Hill & L.A.S.Johnson Eucalyptus citriodora Hook. Eucalyptus macula