The familiar tree known as the eucalyptus is indigenous to Australia. This popular quick growth tree is now cultivated in many other countries. The tree is one of the quickest growing tree species around; it is also among the world's biggest and tallest trees. The eucalyptus grows successfully in many places with varied soils and climate. When fully grown, some sub-species of this tree can cross two hundred fifty feet in height. The eucalyptus is an efficient dry land tree, putting out a vast network of roots underground to probe for water. The efficient ability of the eucalyptus at scrounging water from the soil has been applied to great effect in draining marshy and water logged areas in land reclamation programs. This characteristic of the tree has proven to be of the greatest help in the complete reclamation of water bogged malarial swamps in many countries with hot and humid climates. For example, the malarial swamps in the Central American country of Guatemala were largely reclaimed by planting a large number of eucalyptus trees in the marshy waste lands that acted as the breeding grounds of mosquitoes.
Eucalyptus trees are characterized by the possession of bluish white colored bark, the bark easily peels off and many trees shed the bark. The tree bears green branchlets and foliage at the top. A white and waxy bloom coats the tender shoots and the leaves. The leaves of eucalyptus plants are dissimilar in shape and other characteristics, while the bluish green hued and sticky tender leaves tend to grow in opposite venation and are heart shaped, bluish-green, the mature green colored leaves grow in alternate venation, they are also lance shaped and have a smooth texture. Eucalyptus has a peculiar pungent smell; this is due to the aromatic oil contained in the leaves and buds of the plant. This pungent scent is given off by crushed or bruised leaves.
Eucalyptus leaves are harvested and the aromatic oil is extracted for commercial purposes. For example, the essential ingredient in balms like the Vicks Vapo-Rub and other herbal remedies contains the aromatic eucalyptus oil. Vicks Vapo-Rub is a very popular over the counter mentholated herbal preparation and many millions of people have been using this remedy for many years to locally alleviate the symptoms of various respiratory disorders, particularly the symptoms of chronic asthma and bronchitis. The topical remedy is used by placing a small amount of the ointment on the chest of the affected person, following by a slow and gentle rub using the forefingers in a circular motion to spread out the soothing balm on the chest. A flannel cloth is at times laid over the skin rubbed with the Vapo-Rub - this results in warm stimulating and penetrating effect persisting for a longer time on the skin.
Among all native tree species in Australia, the Eucalyptus globulus species of tree is considered to be one of the most widely cultivated trees as far as commercial and non-commercial acreage is concerned. This tree species can be easily spotted at many of the parks and gardens in all Australian cities and urban centers. This tree has also been naturalized in many countries around the world. For example, Algeria on the North African coast, Brazil in South America, France, Spain, Portugal and India all have fully naturalized and teeming populations of eucalyptus plants - the eucalyptus is almost cosmopolitan in distribution in the contemporary world and grows all over the world. Many Californians even regard the eucalyptus as a native species and are unaware that it is an introduced species due to its huge success there.
Eucalyptus is classified into four primary recognized sub-species - each of which differs from the other trees, in a range of physical or morphological characteristics that includes the type of bark, the habit and the arrangement of flowers when in bloom.
The Eucalyptus tree known as the “Tasmania blue gum” is botanically known as the - E. globulus tree. This sub-species of eucalyptus is found growing in the eastern and south-eastern parts of the island of Tasmania including a population in the islands of Bass Strait. This sub-species of eucalyptus can also be found in some areas in the southern part of the state of Victoria. This sub-species of eucalyptus is characterized by bearing flowers singly on the axils of the leaf. The bark of this sub-species is rough and most of the bark at the base of the tree trunk never peels off. The state of Tasmania uses the flowers of this sub-species of Eucalyptus as its floral emblem.
The sub-species of Eucalyptus called the “Maiden's gum” is botanically called the-E.globulus maidenii-tree. This sub-species of the eucalyptus can be found growing in North eastern regions of the state of Victoria and in south-eastern New South Wales. The flowers of this sub-species of eucalyptus form into groups of seven along the axils of the leaf when in bloom. The bark at the base of the trunk normally peels away in this tree type.
The sub-species of Eucalyptus called “Gippsland blue gum” is known as the “E.globulus pseudoglobulus” to botanists. This sub-species of eucalyptus can be seen growing in south eastern New South Wales State, Flinders Island in the Bass Strait as well as in eastern and southern parts of the state of Victoria. This sub-species bears flowers primarily in floral groups of three attached along the axils of the leaves. The bark at the base of the trunk usually peels away leaving the tree base bare.
The sub-species of Eucalyptus called the “Southern blue gum” are known as the E.globulus bicostata to botanist. This sub-species of eucalyptus is mainly found in a number of places along the Great Dividing Range in Australia, extending from the northern region of the state of New South Wales to the western region of the state of Victoria. This sub-species of eucalyptus tends to bear flowers primarily in groups of three on the leaf axils. This sub-species of eucalyptus possesses a rough bark that is usually retained at the base of the tree.
Eucalyptus is cultivated in many parts of the world and is a popular tree for cultivation and reforestation efforts as it is quick growing. The sub-species globulus is especially a popular tree for cultivation in many parts of the world. Some of its characteristics including the pretty and blue-grey - glaucous - juvenile foliage and its rapid growth make it ideal for land wasteland reclamation and reforestation efforts. This sub-species may not be suitable for all locales and places as it may be too big and demand too much space for average sized sub-urban blocks. This sub-species of the eucalyptus also has a very robust and vigorous root system that fans out rapidly underground - the spreading roots can damage housing and underground pipes if the tree is not sited at a suitable location.
The globulus sub-species of the eucalyptus possess an open textured wood that is marked off by distinct growth rings - which can be used to identify the age of the tree. This wood of this sub-species is also hardy and strong as well as being durable; it therefore finds use in a variety of roles and manufactures, such as in the manufacture of railway sleepers, to make piles and planks, the paper industry, as well as a being a source of wood oil and in the manufacture of honey. Wood of this sub-species has also being used as a fuel and the tree coppices well. The quantity of volatile oil obtainable from this sub-species is relatively low compared to the other sub-species of eucalyptus. However, this sub-species still serves as a substantial source of volatile oil and commercial extraction of the oil from this sub-species species is carried out on an extensive scale in Spain and Portugal and on a lesser scale in other places. The soap making and perfumery industry utilizes this pale yellow volatile oil in the manufacture of a variety of products.
The Australian aborigines traditionally used various herbal remedies made from different parts of the Eucalyptus to treat fevers and all kinds of infections. These days, remedies made from the eucalyptus are used by many people all over the world for the treatment of these types of complaints. The potent anti-septic and anti-viral power of the eucalyptus makes it very helpful to treat colds, flu, and it is often used as a gargle to treat sore throats.
Other medical uses
Habitat and cultivation
The eucalyptus is an indigenous Australian species, originally it was found only there. Due to the great popularity of the eucalyptus as a quick growth tree, it is now extensively cultivated in plantations around the world in countries that have a tropical, sub-tropical or temperate climatic regime. Eucalyptus trees are quick growing hardy species, however, it has been increasingly realized that planting the eucalyptus plants without planning can bring great ecological disruption and environmental problems to any area. One of the primary reasons is that these trees often absorb huge volumes of water from the ground and this can prevent the normal growth of native plant species - often endangering the local plant community. However, the water absorption capability of the eucalyptus species is considered very beneficial in some cases, especially when trees are planted to help dry up marshy areas - thus lowering the risk of malaria in an area. The leaves of cultivated trees are harvested and subjected to distillation to obtain the essential oil or they are dried and used for other purposes.
In cultivation, the ideal site to grow eucalyptus is in sites that have a good exposure to sunlight. The tree grows best in soils that are moderately fertile and are well drained. Eucalyptus also prefers moisture retentive and circum-neutral soils and gives optimal growth in such soils. However, as already mentioned the eucalyptus is a hardy plant and can easily grow with success in most soil types. It is a strong plant and can tolerate even poor and very dry soils. The tree is tolerant of even those soils that are particularly low in essential mineral elements required by most other plant species. One eucalyptus has been grown on a site, the established mature trees become very tolerant to drought and prolonged dry periods. When planting the eucalyptus, it is best to avoid planting in frost pockets or along windy sites. Growing eucalyptus plants usually need a sheltered position; the young eucalyptus plants may not be able to tolerate extreme cold temperatures and will also not grow well if exposed to winds that are dry or desiccating during the crucial early growth stage. Eucalyptus plants are tolerant of moderate rainfall and are tolerate annual precipitation from 80 to about 160cm. The species also tolerates fluctuations in annual temperature ranging from 16 to 20°C. As the eucalyptus is a sub-tropical species, it does not possess the deciduous habit of stopping growth in cold weather and trees will continue to grow until it turns too cold for any growth to occur. This factor makes the eucalyptus plants vulnerable to physical and tissue damage from the appearance of sudden cold conditions and frosts. Eucalyptus trees resist the cold better, when the fluctuation in the temperature is much more gradual such as in woodlands and sub-temperate areas, often stopping growth and becoming dormant - eucalyptus plants grown in such conditions or areas are much more cold resistant than plants grown in temperate or colder regions. The eucalyptus trees also survive much better and grow at an optimal rate if provided with a deep mulch in the site around the roots - this mulching prevents the freezing of the soil and aids the resistance of the trees to cold weather. The Genus Eucalyptus is nevertheless one of the most adaptable plant genuses around and the trees are remarkably hardy in all kinds of weather conditions. The hardiness of each generation can undergo a dramatic as seeds from subsequent generations of plants grown in the temperate zones are planted - the tree adapts to the local conditions in a few generations. Among all the different eucalyptus sub-species, the “Tasmanian blue gum” with a total number covering about 800,000 ha in dozens of countries around the world is considered to the most extensively planted sub-species of eucalyptus. The Tasmanian blue gum is the eucalyptus species of choice in S. Europe and can commonly be seen there, particularly in countries such as Italy, Spain and Portugal. This sub-species of eucalyptus is used as a source form commercial timber, as a tree for soil stabilization in degraded lands and as a source of the essential eucalyptus oil found in the leaf extract. Eucalyptus trees are also extensively planted in bogs and marshy areas to help lower the wetness of the land in land reclamation projects or to rid such areas of breeding mosquitoes - the high transpiration rate of eucalyptus plants is the reason for their efficiency in clearing excess water from bogs and marshes. Eucalyptus plants are shallow rooting during the early growth periods and have to be planted at the permanent sites while they are small to protect them from the danger of high winds. Eucalyptus saplings do not tolerate disturbance to the root system very well and are best grown in containers initially before they are taken for planting at permanent sites. Eucalyptus trees are also favored by apiarist as the nectar rich flowers are a good source of nectar for bees. The typical balsamic eucalyptus aroma is given off by leaves when they are slightly bruised - a stand of eucalyptus trees can be identified by the presence of this peculiar aromatic smell.
Eucalyptus trees are propagated using stored seeds. The seeds are sown on the soil surface either in February or March, usually in seedbeds within greenhouse - sites with good exposure to incoming sunlight is preferred. The best method to grow seedlings of sub-species that are from high altitudes is to subject them to cold stratification for six or eight weeks. As soon as the second sets of seed leaves appear, the seedlings are placed into individual pots - this is done because, it becomes difficult to successfully move or transplant the seedlings at a later stage. Early in the summer, seedlings are planted out into the permanent positions and at this stage, usually given them some protection from the cold during the winter of the first year of growth. Eucalyptus seeds are often sown in June as well, in such a case, the young trees are only planted at the permanent site late in the spring of the next year. Eucalyptus seeds are viable for long periods of time and can be stored for years on end.
There have been numerous and extensive research into the essential oil of the eucalyptus in the last half century. The essential oil has been shown to possess a distinct and potent antiseptic action as well as a power to dilate the bronchioles and respiratory passages in the pulmonary system. The main constituent of the oil is a compound called cineole, however, the potency of cineole when used alone is weaker compared to the whole essential oil - other compounds in the oil are also responsible for the beneficial effects in addition to the cineole.
The volatile oil contains about 70% eucalyptol (1, 8-cineole), as well as pinene, limonene, alpha-terpineol, and linalool. While it is similar to the oils of related species, this oil appears to be better tolerated by the skin.