Do you know how the beautiful mountains of South India, the ‘Nilgiris’, got their name? In the mid- 19th century, a species of tree soaring 65m tall, with a smooth steel-blue bark, was planted in these mountains on a large scale, to meet the locals’ requirement of fuel wood. The tree was a native of Australia, a species of eucalyptus called the blue gum. The blue-tinged foliage and trunk of this tree gave the Nilgiris their characteristic color.
In Australia, eucalyptus, especially ones that have a smooth bark, are called gum trees, because the trees exude a sticky resin. There are 600 species of eucalyptus growing in a variety of habitats, ranging from the snow-clad Australian Alps to the semi-arid desserts. Since eucalyptus are fast-growing, resistant to drought and provide useful timber, over 200 species have been introduced all over the world, including India. In fact, millions of eucalyptus trees have turned the treeless wastelands and semi-arid areas of Rajasthan and Punjab green.
Eucalyptus trees have a number of uses. They provide oil and tannins besides timber. The trees are planted for their shade and to prevent soil erosion by the wind and rain. Koalas feed solely on eucalyptus leaves and the honey possum lives on the nectar of eucalyptus flowers. Less than a dozen of the eucalyptus species are exploited for their oil. The oil is extracted from the leaves by steam distillation. Eucalyptus oils are used in medicines, perfumes, and disinfectants. Some eucalyptus produce oil rich in cineole which is an important ingredient in ointments, inhalants, lozenges and gargles. Others contain phellandrene used in disinfectants and liquid soaps. Piperitone or peppermint eucalyptus lend their icy coolness to synthetic menthols. Perfume manufacturers use oils with citronella, which has a pleasant fragrance.
The giant mountain ash or eucalyptus regnans is the tallest hardwood tree in the world. It towers to a height of 100 meters or more.