Backhousia citriodora
Lemon Myrtle
Lemon Myrtle
Wikipedia links: Angiosperms > Eudicots > Rosids > Backhousia citriodora
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Common name: Lemon Myrtle
Also, lemon myrtle, lemon scented myrtle, lemon scented ironwood
Other common names are sweet verbena tree, sweet verbena myrtle, (lemon scented verbena is another species), and lemon scented backhousia
The common name reflects the strong lemon smell of the crushed leaves
"Lemon scented myrtle" was the primary common name until the shortened trade name, "lemon myrtle", was created by the native foods industry to market the leaf for culinary use
Conservation status: . . .
Etymology:
Was given the botanical name Backhousia citriodora in 1853 after the English botanist, James Backhouse
Flowers:
The flowers are creamy-white, 5–7 mm in diameter
Produced in clusters at the ends of the branches from summer through to autumn
After petal fall the calyx is persistent
Fruit:
Leaves:
Opposite and lanceolate
5–12 cm long and 1.5–2.5 cm broad
Glossy green, with an entire margin
Stem & branches:
Roots:
Habit:
An evergreen tree up to 6 m in height, but is often smaller
Habitat:
Subtropical rainforests
Distribution:
Endemic to central and south-eastern Queensland
A natural distribution from Mackay to Brisbane
Additional notes:
Identification
Lemon myrtle is sometimes confused with "lemon ironbark", which is Eucalyptus staigeriana
Essential oils
Lemon Myrtle essential oil is available in a clear glass vial
It 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%
Oil yield of 1–3% from fresh leaf
It is the highest natural source of citral
The citronellal chemotype:
Uncommon
Can be used as an insect repellent
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
Culinary
Dried and crushed Lemon myrtle leave Lemon myrtle is one of the well known bushfood flavours and is sometimes referred to as the "Queen of the lemon herbs"
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
The dried leaf has free radical scavenging ability
Antimicrobial
The oil possesses antimicrobial properties; however the undiluted essential oil is toxic to human cells in vitro
When diluted to approximately 1%, absorption through the skin and subsequent damage is thought to be minimal
Lemon myrtle oil has a high Rideal–Walker coefficient, a measure of antimicrobial potency
Has been investigated as a treatment for skin lesions caused by molluscum contagiosum virus (MCV)
This is a disease affecting children and immuno-compromised patients
Nine of sixteen patients who were treated with 10% strength lemon myrtle oil showed a significant improvement, compared to none in the control group
A study in 2003 which investigated the effectiveness of different preparations of lemon myrtle against bacteria and fungi concluded that the plant had potential as:
an antiseptic
a surface disinfectant, or
an anti-microbial food additive
The oil is a popular ingredient in health care and cleaning products, especially soaps, lotions, skin-whitening preparations and shampoos
Cultivation
Lemon myrtle is a cultivated ornamental plant
It can be grown from tropical to warm temperate climates
May handle cooler districts provided it can be protected from frost when young
In cultivation it rarely exceeds about 5 m 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
Seedlings go through a shrubby, slow juvenile growth stage, before developing a dominant trunk
Lemon myrtle can be propagated from cuttings, but is slow to strike
A study into the plant growing adventitious roots found that "actively growing axillary buds, wide stems and mature leaves" are good indicators that a cutting will take root successfully and survive
A further study on temperature recommended glasshouses for growing cuttings throughout the year
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 NSW
A 2009 study has suggested that drying lemon myrtle leaves at higher temperatures improves the citral content of the dried leaves, but discolours the leaves more
Myrtle rust
A significant fungal pathogen, myrtle rust (Uredo rangelii) was detected in lemon myrtle plantations in January 2011
Myrtle rust severely damages new growth and threatens lemon myrtle production
Controls are being developed
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