In the late 1700’s, early botanists first tackled the job of describing the more than 500 species of eucalyptus. The job isn’t yet complete. Botanists are still discovering new varieties and hybrids and revising old classifications.
The genus name for eucalyptus is the Greek ‘Eu kalyptos’ which means ‘well-covered’. It refers to the flower buds which are cone shaped and have a lid-like structure that opens as the flowers mature. Eucalyptus trees exude a sticky, tannin-rich substance known – as kino. Because of its astringent properties, kino has a history of medicinal use.
In fact, 19th century British colonists noting the fragrant, medicinal aroma of eucalyptus groves, planted the ‘fever trees’ in tropical fever-ridden districts throughout the Empire to help drive – away insects and contagious disease. The extensive root system of these trees also helped dry out water-logged soils, deterring disease-carrying insects, especially mosquitoes, which need standing water to breed.
Today, most eucalyptus oils come from California as well as Australia, Tasmania, Brazil, China, India, Portugal, Russia and Spain. The oils are steam-distilled from the fresh leaves and branch tips.
The initial distillation yields a darker yellow oil than most commercially available oil. The crude oil is then redistilled, removing less stable constituents that cause it to deteriorate more rapidly. The second distillation also produces a more consistent product.
People familiar with the sweet, fresh, woody aroma of green eucalyptus leaves are often surprised by the more medicinal aroma of the oil. The difference is explained by the chemical changes that naturally occur when heat is applied during distillation and redistillation. Also, some aroma constituents in the living plant are not a part of the essential oil. For those who prefer a sweeter aroma, the lemon-scented oil is a good a1ternative.
There are three varieties of eucalyptus oils: industrial; perfumery oils; and medicinal and aromatherapy oils.
The species of tree and its essential oil used in industry contains constituents used in floatation. It is a process used mainly in the mining industry to separate ore particles from unwanted minerals.
The lemon-scented eucalyptus oil used in perfumery contains nearly 90 percent citronella along with geraniol. Both of these constituents are primary fragrancing compounds in the perfume and cosmetic industry.
The primary active constituent in the medicinal/aromatherapy eucalyptus species is cineol, also known as eucalyptol. The medicinal, camphoraceous aroma of cineol is activating, vitalizing and energizing. Hundreds of cold and flu preparations such as cough drops, throat lozenges and chest rubs use eucalyptol.
By experimenting with the wide variety of eucalyptus essential oils available, you can chart a truly personal course through the garden to the aromatic benefits of eucalyptus essential oils.