Practical
Plants

Eucalyptus citriodora

Lemon-Scented Gum

a perennial woody evergreen member of the Eucalyptus genus in the family Myrtaceae.

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Taxonomy and growth

Family
Myrtaceae
Life cycle
perennial
Foliage
evergreen
Woodiness
woody
Growth rate
vigorous
Height
45 m
Fertility
Bees
Flower type
hermaphrodite
Pollinators
Bees

Uses

Toxicity

Toxicity warning. The historical record reports a hazard for this plant. Do not use it to decide which parts are safe to eat or use medicinally.

This section contains historical Plants For A Future notes marked noncommercial.

Citronellal, an essential oil found in most Eucalyptus species is reported to be mutagenic when used in isolation[14]. In large doses, oil of eucalyptus, like so many essential oils has caused fatalities from intestinal irritation[14]. Death is reported from ingestion of 4 - 24 ml of essential oils, but recoveries are also reported for the same amount[14]. 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[14].

Edible uses

This section contains historical Plants For A Future notes marked noncommercial.

Produces a sweet manna-like substance that is scraped off the leaves and eaten[8].

Plant part
Sap
Product or use
Manna

Medicinal uses

Historical medicinal uses. These records describe reported uses. They do not establish safety or effectiveness. Ask a qualified health professional before using any plant medicinally.

This section contains historical Plants For A Future notes marked noncommercial.

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[13]. The essential oil is a common ingredient in many over-the-counter cold remedies[13].An essential oil obtained from the leaves is antibacterial[4]. 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[15]. 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[15]. Some caution is advised, however, because like all essential oils, it can have a deleterious effect on the body in larger doses[15]. An oleo- resin is exuded from the tree[10]. It can also be obtained from the tree by making incisions in the trunk[15][4]. This resin contains tannin and is powerfully astringent, it is used internally in the treatment of diarrhoea and bladder inflammation[15][4][10], externally it is applied to cuts etc[15][4].

Product or use
Antibacterial
Product or use
Astringent

Material uses

This section contains historical Plants For A Future notes marked noncommercial.

A lemon-scented essential oil is obtained from the leaves[15][16][18][14]. It is used, especially in perfumery but also medicinally[17][4]. The leaves yield between 0.5 to 2.0% essential oil[11]. This species is a very rich source of citronella, which is much used in the perfumery industry[15][6]. Some batches of the essential oil contain 98% citronella[15]. Glabrous leaves may contain oil with 65.5% citronellal, 12.2% citronellol, and 3.6% isopulegol; hairy leaves contain more oil with 86.6- 90.1% citronellal, 4.6 - 6.0% citronellol, and 0.7 - 0.8% isopulegol, 1-pinene, b-pinene, and isovaleric aldehyde are also recovered[14]. The leaves and the essential oil are used as an insect repellent[6]. The leaves are also an ingredient of pot-pourri[10]. The bark may contain up to 12% tannin[14]. The wood is good for saw-timber and is used for general construction, poles, railroad ties, and tool handles[17][14]. Firewood yields run 10 - 21 m3/ha/yr[14]. The hard heavy wood (sp. grav. 0.75 - 1.1) burns steadily and makes a good charcoal with an ash content of 1 - 2%[14].

Product or use
Essential
Product or use
Pot-pourri
Product or use
Repellent
Product or use
Tannin
Product or use
Wood

Environment

Range
Australia - Queensland.
Habitat
Usually found in heavy soils[18], but also succeeding on deep sandy loams in coastal regions[5].
Light
full sun
Shade tolerance
no shade
Water
high
Hardiness
Zone 10+
Soil textures
sandy, loamy, clay
Soil pH
acid, neutral, alkaline
Drainage
well drained
Tolerances
drought
Tolerates Nutritionally Poor Soil
No
Drought
tolerant

Propagation

This section contains historical Plants For A Future notes marked noncommercial.

Seed - surface sow February/March in a sunny position in a greenhouse[2][19][3]. Species that come from high altitudes appreciate 6 - 8 weeks cold stratification at 2°c[9]. 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. Plant out into their permanent positions in early summer and give them some protection from the cold in their first winter. The seed can also be sown in June, the young trees being planted in their final positions in late spring of the following year. The seed has a long viability[9].

Cultivation

This section contains historical Plants For A Future notes marked noncommercial.

Prefers a sunny position in a moderately fertile well-drained moisture retentive circum-neutral soil[9]. Tolerates poor and dry soils, especially those low in mineral elements[9]. Established plants are drought tolerant[9]. Does not succeed in frost hollows or in windy sites[1]. The plant is said to grow best where the annual rainfall, mostly summer, is 60 to 130cm, with a 5 - 7 month dry season, withstanding high temperatures (29 - 35°C mean monthly maximum) and light frosts. It succeeds in tropical and subtropical arid to semiarid zones, in infertile clays, laterites, poor and gravelly soils and podzols, preferably well drained[14]. A very fast growing species but it is not very hardy in Britain[7]. It might succeed outdoors in the mildest areas of the country. 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[9]. 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[9]. Cultivated in warm temperate areas for its essential oil, it thrives in a Mediterranean climate[17][18]. Eucalyptus monocultures are an environmental disaster, they are voracious, allelopathic and encourage the worst possible attitudes to land use and conservation[9]. The trees cast a very light shade[18]. Flower buds are formed in the summer prior to flowering and seed capsules need at least a further year in which to ripen[2]. 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[12]. They strongly resent root disturbance and should be container grown before planting out into their permanent position[2]. The flowers are rich in nectar and are a good bee crop[9].

References

  1. Brooker. M. I. A Key to Eucalypts in Britain and Ireland. HMSO 1983-00-00 ISBN 0-11-710192-3

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  2. Bean. W. Trees and Shrubs Hardy in Great Britain. Vol 1 - 4 and Supplement. Murray 1981-00-00

    ↩1↩2↩3

  3. Rice. G. (Editor) Growing from Seed. Volume 2. Thompson and Morgan. 1988-00-00

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  4. Lassak. E. V. and McCarthy. T. Australian Medicinal Plants.

    ↩1↩2↩3↩4↩5

  5. Brooker. S. G., Cambie. R. C. and Cooper. R. C. Economic Native Plants of New Zealand. Oxford University Press 1991-00-00 ISBN 0-19-558229-2

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  6. Cribb. A. B. and J. W. Useful Wild Plants in Australia. William Collins Pty Ltd. Sidney 1981-00-00 ISBN 0-00-216441-8

    ↩1↩2

  7. Taylor. J. The Milder Garden. Dent 1990-00-00

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  8. Facciola. S. Cornucopia - A Source Book of Edible Plants. Kampong Publications 1990-00-00 ISBN 0-9628087-0-9

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  9. Huxley. A. The New RHS Dictionary of Gardening. 1992. MacMillan Press 1992-00-00 ISBN 0-333-47494-5

    ↩1↩2↩3↩4↩5↩6↩7↩8↩9

  10. Bown. D. Encyclopaedia of Herbs and their Uses. Dorling Kindersley, London. 1995-00-00 ISBN 0-7513-020-31

    ↩1↩2↩3

  11. Chopra. R. N., Nayar. S. L. and Chopra. I. C. Glossary of Indian Medicinal Plants (Including the Supplement). Council of Scientific and Industrial Research, New Delhi. 1986-00-00

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  12. Genders. R. Scented Flora of the World. Robert Hale. London. 1994-00-00 ISBN 0-7090-5440-8

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  13. Chevallier. A. The Encyclopedia of Medicinal Plants Dorling Kindersley. London 1996-00-00 ISBN 9-780751-303148

    ↩1↩2

  14. Duke. J. Handbook of Energy Crops - 1983-00-00

    ↩1↩2↩3↩4↩5↩6↩7↩8↩9↩10↩11

  15. Grieve. A Modern Herbal. Penguin 1984-00-00 ISBN 0-14-046-440-9

    ↩1↩2↩3↩4↩5↩6↩7↩8↩9

  16. Uphof. J. C. Th. Dictionary of Economic Plants. Weinheim 1959-00-00

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  17. Usher. G. A Dictionary of Plants Used by Man. Constable 1974-00-00 ISBN 0094579202

    ↩1↩2↩3

  18. Kelly. S. Eucalypts. (2 volumes.) Nelson, Melbourne 1969-00-00

    ↩1↩2↩3↩4

  19. Sheat. W. G. Propagation of Trees, Shrubs and Conifers. MacMillan and Co 1948-00-00

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