Eucalyptus globulus, and other species, -Western-

Eucalyptus species used for oil production in Australia.
The most important standard in the British Pharmacopoeia is that the oil must have a minimum cineole content of 70 per cent if it is to be of pharmaceutical quality.

Eucalyptus polybractea
Commonly known as "Blue Mallee" is a small mallee type tree. It grows only in natural stands in the districts north and north-west of Bendigo in Victoria and in the West Wyalong area in New South Wales. The yield of oil from the leaves and terminal branchlets varies between 1.5 and 2.5 per cent. Young material is richer in oil and the time of year also influences the yield. The crude oil is high in cineole and usually assays at between 80 and 88 per cent. The absence of aliphatic aldehydes contributes to the pleasant aroma of the crude oil. The crude oil which is yellow to brown becomes a pale straw colour (rarely water white) on rectification. This high quality medicinal oil is now the principal pharmaceutical grade of eucalyptus oil sold in Australia and accounts for over one-half of the exports.

Eucalyptus radiata var. australiana, commonly known as "narrow-leaved Peppermint", is a medium sized tree with fibrous bark. It occurs in extensive areas in Victoria and the south coast districts and southern highlands of New South Wales. The yield of oil from the leaves and terminal branchlets averages between 3 and 3.5 per cent. The lowest yield, usually around 2.6 per cent is encountered during the winter months. The crude oil has a cineole content of 65 - 70 per cent and because of the terpineol and citral constituents of the oil it has a very refreshing aroma. The crude oil is usually a very pale lemon colour but is colourless on rectification. Production of this pharmaceutical grade oil has fallen as the cost of production has become too high. The leaves cannot be mechanically harvested in the same way as E. polybractea because of the steep terrain of the natural stands.

Eucalyptus dives var. "C" belongs to the "broad-leaved Peppermint" group. It is botanically identical to E. dives (type) but the oils from these otherwise identical species have no resemblance whatsoever in chemical composition. However, the oil from E. dives var. "C" and E. australiana are practically identical in chemical and physical characters. The species grows in good stands in the Tumbarumba-Tumut-Batlow district of New South Wales. The yield of oil from the leaves and terminal branchlets varies from two to four per cent and the oil is colourless. The oil is a good quality medicinal oil.

Eucalyptus dives (type) commonly known as the "broad-leaved Peppermint" grows along the coastal ranges of New South Wales and Victoria. Generally it is a moderate sized tree with a greyish-brown stringy bark. The yield of oil from the leaves and terminal branchlets varies from two to four per cent with the general average being three per cent. The oil of this species contains 1-piperitone (40 - 50 per cent) and phellandrene (20 - 30 per cent). The oil is used industrially for the manufacture of synthetic thymol and menthol.

Eucalyptus australiana var. "B" or E. phellandra is commonly known as one of the "narrow-leaved Peppermints". It occurs extensively on the mountain ranges of New South Wales and Victoria being especially abundant in the Braidwood and south coast districts of New South Wales. It is botanically identical to E. australiana but produces a different type of oil. The yield of oil from the leaves and terminal branchlets averages from 3 to 4.5 per cent of a colourless to pale yellow oil. The oil consists of phellandrene (35 - 40 per cent) and cineole (20 - 50 per cent). The oil has been extensively used for disinfectants, deodorants and many other industrial uses. It is an excellent solvent. Production has fallen dramatically as the selling price for this industrial oil has been too low to justify the hard work and high labour input required.

Eucalyptus globulus was discovered in Tasmania in 1792 by Labillardiere and is commonly known as the "blue gum". No eucalypt has received so much attention from botanists and chemists as this species. It has been cultivated in all parts of the world and the eucalyptus oil from E. globulus is the best known and most used of all eucalyptus oils. While it was distilled in Tasmania in 1880 it is no longer produced in Australia, having been replaced by higher yielding and better quality oils from other species. The yield of oil from the leaves and branchlets averages from 0.75 to 1.25 per cent. The crude oil is a mobile liquid, normally light yellow in colour, with a pronounced odour of the volatile aldehydes which causes coughing and irritation to the mucous membranes. The cineole content is between 60 - 70 per cent and since in many instances the properties of the crude oil do not meet the specifications of most pharmacopoeias the oil has to be rectified to increase the cineole content and to improve its solubility in alcohol. After rectification the oil is water-white.
Because of the volume and availability of this type of oil on the world market it has become the standard eucalyptus oil for buyers everywhere.

Eucalyptus citriodora commonly known as the "lemon scented gum". A large tree often attaining a great height with a smooth whitish pale pink bark. Readily identified by the fragrant "citronella-like" odour of the crushed leaves. It grows extensively in Queensland in natural stands. However, it has been extensively cultivated as an ornamental tree and has been planted for commercial purposes in many countries. The yield of oil from the leaves and terminal branchlets from forest trees varies from 0.5 to 0.75 per cent and from cultivated trees up to 2 per cent. The principal constituent of the oil is citronellal and the oil is used for industrial and perfumery purposes. Large quantities of oil were once distilled in Queensland but Brazil, which has extensive plantations now produces almost all the oil from this species. The last report indicated that there were five million trees of E. citriodora in the state of Sao Paulo, Brazil, being used for oil production.

Eucalyptus polybractea
Considerable improvement has been made in recent years in the harvesting, materials handling and distillation of Eucalyptus polybractea. Continued progress would give Australia an opportunity to regain lost export markets for medicinal eucalyptus oil and would provide a chance to diversify farming activities in low rainfall country areas where the possibilities for other sources of income are limited.
References
bosistos.com.au

Eucalyptus oil plantations
thursdayplantation.com Thursday Plantation Visitor Centre is situated on Gallans Road Ballina NSW 2478 (1km north of Ballina Byron Gateway Airport). 5 minutes north of Ballina and 25 minutes south of Byron Bay. Australia.
yesteryearplantations.com.au harvests Eucalyptus radiata- narrow leafed peppermint. Valley Views, Lot 3 1433 East Gilmore Road Tumut NSW 2720 Australia.
bosistos.com.au harvests Eucalyptus Polybractea- Blue Mallee. 61 - 81 Clarinda Road (PO Box 74) Oakleigh South VIC 3167 Australia.
grdavis.com.au many species of Eucalyptus 80 Bayldon Road Queanbeyan NSW 2620 Australia.