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How Much Do You Know About the Eucalyptus Tree? Check These Facts

Eucalyptus Tree Facts
Did you know that some species of eucalyptus trees are among the tallest trees in the world? You would be amazed at some of the wonderful facts about eucalyptus trees - also known as gum trees.
Sonia Nair
Last Updated: Jan 21, 2018
The very name 'eucalyptus' reminds us of the aromatic oil with a unique smell. Extracted from the leaves of eucalyptus trees, this oil has various medicinal, agricultural, and industrial uses. Apart from extraction of eucalyptus oil, these trees are used for various other purposes. Eucalyptus is also a major source of firewood as well as pulpwood.

Eucalyptus trees belong to the family Myrtaceae, and genus Eucalyptus. More than 700 species of eucalyptus trees have been identified so far, and most of them are natives to the Australian subcontinent. However, many species of eucalyptus are grown in different parts of the world, and some of them are commercially cultivated in tropical and subtropical regions. As they are believed to consume large amounts of water, eucalyptus trees are grown near marshy areas to drain water, and to prevent water-borne diseases. Scroll down for some amazing facts about eucalyptus trees, which are also used for making natural dyes for certain types of fabric.
Eucalyptus Trees - Some Interesting Facts
What is the link between the Blue Mountains and eucalyptus trees? Of course, this mountain range is located in Australia, where you can find eucalyptus trees abundantly. This mountain range may have a bluish hue, when viewed from a distance. It is believed that the bluish tinge is due to the haze created by the evaporated oils from the eucalyptus leaves; hence, the name, Blue Mountains.
The Blue Mountains in Australia
Both koalas and most of the eucalyptus species are natives to Australia. These animals are mainly found in eucalyptus forests, and their staple diet consists of eucalyptus leaves. However, they prefer certain eucalyptus species over others, for feeding purposes. They are adapted to this diet in various ways, and are found to consume around 200 to 500 grams of eucalyptus leaves per day.
If you take a look at the list of the tallest trees in the world, you may come across certain eucalyptus species too. Eucalyptus Regnans is said to be the tallest flowering plant in the world. Otherwise known as Australian mountain ash or swamp gum, it is one of the tallest trees in the world. Eucalyptus Regnans can grow to a height of around 115 meters.
Eucalyptus regnans, the tallest flowering plant
The image below shows the eucalyptus trees in Australian Alps, covered with snow. Snow gum (Eucalyptus pauciflora) is one of the commonly found trees in this region. They are tolerant to the extreme winter temperature in Australian Alps. These trees do not shed leaves during this season, but are adapted to survive the snow. They will bend down, till the branches touch the ground. This will prevent breaking of branches due to the weight of the snow. They can tolerate temperatures as low as -9 °F.
Eucalyptus trees in snow-covered Australian Alps
Rainbow Eucalyptus
This is the most beautiful eucalyptus tree, with a color palette on its bark. Commonly known as rainbow eucalyptus, Eucalyptus deglupta sheds its bark several times a year. Such shedding reveals the inner green bark that gradually changes to different shades of red, blue, and even purple - hence the name, rainbow eucalyptus.
The image shows a didgeridoo, which is an Australian aboriginal wind instrument. Traditionally, it is made from eucalyptus branches that are hollowed out by termites. These insects feed on the inner heartwood of eucalyptus branches, leaving the outer sapwood that contain certain chemicals which can repel termites.
Characteristic Features
Eucalyptus Tree
As mentioned above, there are more than 700 species of eucalyptus trees that differ in size as well as growth habits. While some species grow as shrubs, others are trees that can be small, medium, or very tall. They are divided into four categories - single-stemmed forest trees with a crown, which forms a small part of the whole tree height; single-stemmed woodland trees, which may produce branches; 'mallees', which develop multiple stems from the ground level itself and grow up to 10 meters in height; 'mallets' with dense terminal crowns, relatively long trunks and steeply branching habits; and 'morells' with long, straight trunks and a rough bark. Even the shape of the leaves and the nature of the bark may vary from one species to another.

The shade of eucalyptus trees will be patchy, even if they have a dense crown. This is because, the leaves of these trees usually hang downwards. In fact, this is an adaptation to avoid water loss, by exposing less areas to the scorching sun.
The hanging leaves of an eucalyptus tree
Eucalyptus trees are grown for both commercial and ornamental purposes. Either way, the leaves of this tree are of much significance. It is from the mature leaves that eucalyptus oil is extracted. In general, leaves of adult trees are green in color with a glossy finish. Some species may have leaves with a powdery coating. The shape and size of eucalyptus leaves may vary with different species. While most of the eucalyptus trees are evergreen, there are some species, which lose leaves after the dry season.
Scribbles on Eucalyptus
Certain eucalyptus species develop scribble marks on their smooth bark. These marks are not human-made, but are caused by insect larvae that feed on the surface layer, thereby leaving a trail that may appear scribbled.
Bark of Eucalyptus
Most of the eucalyptus species develop a thick bark that increases the girth of the trunk. Many of them shed the outermost layer of the bark annually, revealing the inner, smooth layer. Others do not shed the bark annually, but it remains as the outermost dried layer. Such eucalyptus trees may retain the rough bark on the entire trunk and branches, or only on the trunk, or at the base of the trunk.

The bark of eucalyptus trees is categorized on the basis of its thickness, nature, manner of shedding, etc. Stringy bark has long fibers, which exfoliate into long pieces that are thick and spongy; tessellated bark is broken into small distinct flakes; ribbon bark sheds long and thin pieces, which resemble ribbons; and iron bark consists of hard and rough pieces, which are deeply furrowed.
Flower and fruit
The showy part of eucalyptus flowers are actually the stamens, and not the petals. The cone-shaped fruits are also called gum nuts, which have valves that allow the seeds to be shed.

Different species of eucalyptus trees have flowers in varying colors. Usually, these flowers are found in white, pink, yellow, and reddish shades. In most species, the buds appear in clusters on a single stalk that develops on the axil of the leaves. During the bud stage, the stamens are covered by the operculum, which is a structure formed by fused sepals or petals. As the buds open, the operculum is forced open and discarded. The shape of the seeds may also vary with different species.
The flowers of eucalyptus
Sap oozing out of the bark
Eucalyptus trees are also known as gum trees, as they exude a sticky sap from the cuts and wounds on the bark.
Common Uses of Eucalyptus Trees
Considering the economic importance of eucalyptus trees, they are being cultivated in large numbers, in various places across the globe. While the leaves are used for extraction of essential oil, eucalyptus wood is popular as firewood as well as pulpwood.
Eucalyptus Oil
Being rich in oil, eucalyptus trees promote wildfire, but they are well-adapted to survive the condition. These trees have epicormic buds beneath the bark. After the fire, these buds produce shoots that grow to new branches. It is said that these buds are connected to the outer surface of the bark through special channels that contain hormones. The hormones get activated with the heat caused by the fire, thereby triggering germination of shoots from the epicormic buds.

1. They drop branches: This is one of the disadvantages of growing eucalyptus trees in areas with human inhabitation. Certain species, like river red gum drop their branches very often, thereby causing damage to person as well as property. This tendency is said to be due to the high resin content in the bark. Another possible reason is diseases that can weaken the wood.

2. They are invasive: Certain species of eucalyptus are said to be invasive, thereby replacing the local flora to a great extent. Such loss of native plants and trees may affect the animals and birds that live in that area.

3. They are flammable: Being rich in oils, eucalyptus trees are highly flammable. Even a small fire can transform to a major wildfire in eucalyptus forests, due to the huge amount of leaf litter, the oil-rich leaves on the trees, and flammable bark.

It is also said that these trees absorb water in very large quantities, and this is the reason why they are planted near wetlands and marshy areas. However, the water-sucking nature of these trees can affect the growth of other plants in the vicinity. It may also affect the ground water levels, if the area has too many eucalyptus trees.
Fallen branches
Invasive eucalyptus trees
Eucalyptus engulfed in fire
Several varieties of eucalyptus are grown for ornamental and commercial purposes. Eucalyptus tree care is not a difficult task, as the tree maintains itself, once established. Though resistant to many pests and diseases, there are some diseases that can cause harm to the trees, which can incur huge losses, if grown for commercial purposes.