Backhousia citriodora

taxobox
name = Lemon myrtle


image_caption = "Backhousia citriodora", garden specimen, in flower
regnum = Plantae
unranked_divisio = Angiosperms
unranked_classis = Eudicots
unranked_ordo = Rosids
ordo = Myrtales
familia = Myrtaceae
genus = "Backhousia"
species = "B. citriodora"
binomial = "Backhousia citriodora"
binomial_authority = F.Muell.|

"Backhousia citriodora" (common names lemon myrtle, lemon scented myrtle, lemon scented ironwood) is a flowering plant in the family Myrtaceae, genus "Backhousia", native to subtropical rainforests of eastern Australia. Other common names are sweet verbena tree, sweet verbena myrtle, lemon scented verbena, and lemon scented backhousia.

It can reach 20 m in height, but is often smaller. The leaves are evergreen, opposite, lanceolate, 5-12 cm long and 1.5-2.5 cm broad, glossy green, with an entire margin. The flowers are creamy-white, 5-7 mm diameter, produced in clusters at the ends of the branches from summer through to autumn, after petal fall the calyx is persistent.

Lemon myrtle was given the botanical name "Backhousia citriodora" in 1853 after the English botanist, James Backhouse. The common name reflects the strong lemon smell of the crushed leaves.

Lemon myrtle is sometimes confused with "lemon ironbark", which is "Eucalyptus staigeriana".

Essential oils

"B.citriodora" has two essential oil chemotypes:

* The citral chemotype is more prevalent and is cultivated in Australia for flavouring and essential oil. Citral as an isolate in steam distilled lemon myrtle oil is typically 90-98%, and oil yield 1-3% from fresh leaf. It is the highest natural source of citral.

* The citronellal chemotype is uncommon, and can be used as an insect repellant. [ Doran, J.C., Brophy, J.J., Lassak, E.V., A. P. N. House, Backhousia citriodora F. Muell. - Rediscovery and chemical characterization of the L-citronellal form and aspects of its breeding system, "Flavour and Fragrance Journal", Volume 16 Issue 5, Pages 325 - 328, 20 Jul 2001. [http://www3.interscience.wiley.com/journal/85006210/abstract?CRETRY=1&SRETRY=0] ]

Uses

Indigenous Australians have long used lemon myrtle, both in cuisine and as a healing plant. The oil has the highest citral purity; typically higher than lemongrass. It is also considered to have a "cleaner and sweeter" aroma than comparable sources of citral - lemongrass and "Litsea cubeba". [ The Aromatic Plant Project [http://www.aromaticplantproject.com/articles_archive/lemon_citrus_scented_oils.html] ]

Culinary

Lemon myrtle is one of the well known bushfood flavours and is sometimes referred to as the "Queen of the lemon herbs", with the new growth preferred for its sweetness. [ The Cook and the Chef, ABC TV. [http://www.abc.net.au/tv/cookandchef/txt/s2353399.htm] ] The leaf is often used as dried flakes, or in the form of an encapsulated flavour essence for enhanced shelf-life. It has a range of uses, such as lemon myrtle flakes in shortbread; flavouring in pasta; whole leaf with baked fish; infused in macadamia or vegetable oils; and made into tea, including tea blends. It can also be used as a lemon flavour replacement in milk-based foods, such as cheesecake, lemon flavoured ice-cream and sorbet without the curdling problem associated with lemon fruit acidity.

Antimicrobial

Lemon myrtle essential oil possesses antimicrobial properties; however the undiluted essential oil is toxic to human cells "in vitro". [Hayes AJ, Markovic B. "Toxicity of Australian essential oil Backhousia citriodora (Lemon myrtle). Part 1. Antimicrobial activity and in vitro cytotoxicity." Food Chem Toxicol. 40(4):535-43 (2002). [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11893412&query_hl=1 PubMed abstract] ] When diluted to approximately 1%, absorption through the skin and subsequent damage is thought to be minimal. [Hayes AJ, Markovic B. "Toxicity of Australian essential oil Backhousia citriodora (lemon myrtle). Part 2. Absorption and histopathology following application to human skin." Food Chem Toxicol. 41(10):1409-16 (2003). [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12909275&query_hl=1 PubMed abstract] ] Use of lemon myrtle oil as a treatment for skin lesions caused by molluscum contagiosum virus (MCV), a disease affecting children and immuno-compromised patients, has been investigated. Nine of sixteen patients who were treated with lemon myrtle oil showed a significant improvement, compared to none in the control group. [Burke BE, Baillie JE, Olson RD. "Essential oil of Australian lemon myrtle (Backhousia citriodora) in the treatment of molluscum contagiosum in children." Biomed Pharmacother. 58(4):245-7 (2004). [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15183850&query_hl=1 PubMed abstract] , [http://www.catie.ca/catienews.nsf/0/66c00b8dec87f33185256ec10062a56b?OpenDocument CATIE summary] ] The oil is a popular ingredient in health care and cleaning products, especially soaps, lotions and shampoos.

Cultivation

Lemon myrtle is a cultivated ornamental plant. It can be grown from tropical to warm temperate climates, and may handle cooler districts provided it can be protected from frost when young. In cultivation it rarely exceeds about 5 metres and usually has a dense canopy. The principal attraction to gardeners is the lemon smell which perfumes both the leaves and flowers of the tree. Lemon myrtle is a hardy plant which tolerates all but the poorest drained soils. It can be slow growing but responds well to slow release fertilisers.

Seedling lemon myrtle go through a shrubby, slow juvenile growth stage, before developing a dominant trunk. Growing cuttings from mature trees bypasses the shrubby juvenile stage. Cutting propagation is also used to provide a consistent product in commercial production.

In plantation cultivation the tree is typically maintained as a shrub by regular harvesting from the top and sides. Mechanical harvesting is used in commercial plantations. It is important to retain some lower branches when pruning for plant health. The harvested leaves are dried for leaf spice, or distilled for the essential oil.

The majority of commercial lemon myrtle is grown in Queensland and the north coast of New South Wales, Australia.

Lemon myrtle history

* Pre 1788 - Aboriginal people use "B.citriodora" for medicine and flavouring.

* 1853 - Scientifically named "Backhousia citriodora" by botanist, Ferdinand von Mueller, with the genus named after friend, James Backhouse, quaker missionary and botanist.

* 1888 – Bertram isolates citral from "B.citriodora" oil.cite book | last = Simonsen | first = J. L. | title = The Terpenes, Vol. I | publisher = Cambridge University Press | date = Second Ed., 1953 | pages = 83–100 ] , and Messrs. Schimmel and Co., Dresden, write about the essential oil as having “…probably a future.”

* 1900s-1920s - "B.citriodora" distilled on a small-scale commercial basis around Eumundi, Queensland.

* 1920s – Discovery of antimicrobial qualities of steam-distilled "B.citriodora" oil, by A.R. Penfold and R.Grant, Technological Museum, Sydney.

* 1940s – Tarax Co. use "B.citriodora" oil as a lemon flavouring during World War II.

* 1950s - Some production of oil carried out in the Maryborough and Miriam Vale areas from bush stands by JR Archibold [ Rainforest fragrances. [http://www.lemonmyrtlefragrances.com.au/site/lemon_myrtle.html] ] , but the small industry falls into decline.

* 1989 – "B.citriodora" investigated as a potential spice and commercial crop by Peter Hardwick, Wildnerness Foods Pty Ltd, in cunjunction with gas chromatography analysis of "B.citriodora" selections by Dr Ian Southwell, The Essential Oils Unit, Wollongbar Agricultural Institute.
* 1990 – Restaurants and food manufacturers supplied with dried "B.citriodora" leaf by Vic Cherikoff, Bush Tucker Supply Pty Ltd, produced by Russel and Sharon Costin, Limpinwood Gardens.

* 1991 – "B.citriodora" plantation established by Dennis Archer and Rosemary Cullen-Archer, Toona Essential Oils Pty Ltd, ; and subsequent commercial supply of plantation produced "B.citriodora" oil in 1993.

* 1997 – Large-scale plantations of "B.citriodora" established in north Queensland, by Australian Native Lemon Myrtle Ltd.

* Late 1990s – "B.citriodora" begins to be supplied internationally for a range of flavouring, cosmetic and anti-microbial products. Agronomic production of "B.citriodora" starts to exceed demand.

* 2004 – Monograph published on "B.citriodora" by Toona Essential Oils pty Ltd.

* 2008 - Lemon myrtle sells out in London after Jamie Oliver describes it as "Pukka" on his TV show.

References

*
* [http://www.anbg.gov.au/cgi-bin/apx?taxon_id=49554 APNI Australian Plant Name Index]

Footnotes

External links

* [http://guruna.com/forum/index.php Australian Bushfood and Native Medicine Forum]
* [http://www.dining-downunder.com/shop/index.php?main_page=product_info&cPath=1&products_id=33 Lemon Myrtle] from Vic Cherikoff
* [http://www.lemonmyrtle.com.au Broad range of lemon myrtle products and recipes]
* [http://allaboutlemonmyrtle.com ALL ABOUT LEMON MYRTLE JAPAN]