The Eucalyptus Tree
Eucalyptus Gum Trees are a very large genus of evergreen trees, confined to Australia, except four species of Malayan origin. These trees determine the appearance of the Australian landscape, for eucalypts are more widely distributed than any other genus of trees in this country. Many of the large forest species are valuable timber trees, of very hard texture, so that they are commonly known as hardwoods. Eucalyptus rostrata (Red Gum) produces a particularly durable wood, red in colour, that is used for house-stumps and fence posts; it is resistant to white ants. E. diversicilor (Karri Gum) furnishes a very famous red wood of great durability.
Experts differ on ways of classifying eucalypts, but some consider the main feature for classification to be the bark which may be smooth, scaly, fibrous or furrowed and coloured black, white, pink, bluish, brown or reddish and patterned in streaks, blotches or mottled patches of yellow, olive green, red or brown. Eucalypts are not good shade trees, because the leaves hang vertically with their edges towards the sun. Some species are among the tallest hardwood trees in the world and are also the world's tallest flowering plants. The mountain ash sometimes exceeds 90 m, and one measured in 1880 was over 114 m tall. However, although tall, eucalypts do not have a large girth, and even the huge karri trees seldom exceed 2-3 m in diameter. It is not easy to tell the age of eucalypts by growth rings because, after about 80 years, the rings are indistinct and too close together, but some of the large red gums are estimated to be several centuries old.
Eucalypts are divided into groups according to the type of their hark, and are known as Stringy Bark, when the bark is brown and fibrous; Iron Bark, when the bark is rough and corrugated; Box Trees have bark of a type intermediate between these two; those popularly known as Gums have smooth greyish, pale green, or somewhat mottled smooth bark. In many trees the bark is deciduous, as in E. viminalis (Manna Gum). It is of interest to note that the Manna Gum
is the species on which the koala bear lives.
One group, known as Flowering Gums, has valuable ornamental trees. Most of these are native to Western Australia, and many of them are quite dwarf trees
Eucalyptus flowers are of unique formation. The sepals and petals are united into a lid or cover which falls off as the flower opens. The stamens, which are numerous and highly coloured, form the decorative part of the flower. The fruit is a dehiscent capsule with from three to five carpels, and is commonly known as a nut.
Eucalypt plantations have been established in many parts of the world, including France, Spain, Italy, Egypt, Israel and North and South America. In California and some states of Brazil, eucalypts are a conspicuous feature of the landscape, and many local people regard them as being native trees.