Eucalyptus (Gum Tree)
is a genus of flowering trees and a few shrubs in the family Myrtaceae, comprising more than 700 species. Most of the species are native to Australia, and a few are found in New Guinea, Indonesia, and the Philippine achipelago. Only 15 species occur outside Australia and only 9 do not occur in Australia. Species of Eucalyptus are cultivated throughout the tropics and subtropics regions, including the Americas, Europe, Africa, the Mediterranean Basin, the Middle East, China and the Indian Subcontinent.
Eucalyptus is also known as Gum tree because many species exude copious sap from any break in the bark. The plant is grown mostly for its attractive silvery foliage and peeling bark. Although most of the trees will grow large, they respond well to pruning and can be kept small enough for planting in gardens. The juvenile leaves, which are like small silver-grey coins, are usually more attractive than the mature foligae.
Nearly all Eucalyptus are evergreen but some tropical species lose their leaves at the end of the dry season. As in other members of the myrtle family, Eucalyptus leaves are covered with oil glands. Its oil can be used for cleaning and functions as a natural insecticite. The copious oils produced are an important feature of Eucalyptus.
Eucalyptus has distinctive flowers and fruits (capsules or gumnuts). The flowers have numerous fluffy stamens which may be white, cream, yellow, pink or red. The flowers have no petals but instead decorated themselves with the colorful, showy stamens. The flowers also produce a great abundance of nectar, a source of food for pollinators including insects, birds, bats and possums.
The appearance of the Eucalyptus bark varies with the age of the plant, the manner of the bark shed, the length of the bark fibres, the degree of furrowing, the thickness, the hardness and the color. All mature Eucalypts put on an annual layer of bark, which contribute to the increasing diameter of the stems.
An essential oil extracted from the Eucalyptus leaves contains compound that are powerful natural disinfectants and can be toxic in large quantities. However several marsupial herbivores, notably koalas and some possums, are relatively tolerant of it. The close correlation of these oils with other more potent toxins called formylated phloroglucinol compounds allows koalas and other marsupial species to make food choices based on the smell of the leaves. These compounds are the most important factor in making leaf choices for koalas.
(cider gum), 25 x 15 m, grows into dense single or multi-stemmed tree. It can however, be pruned hard and grown as a shrub in a mixed border. The regular pruning also encourage the production of juvenile leaves, which are like silver coins.
(cabbage gum), 20 x 15 m, is a dense and spreading tree. The whitish bark sheds to reveal brown or green patches. The cream-colored flowers are borne from late spring to summer.
(snow gum) has blue-grey, oval juvenile leaves, and sickle-shaped mature leaves.
Eucalyptus grows well in sun, in moisture-retentive, neutral to acid soil. Protect the plants from cold winds. propagation is by seed in spring or summer. Silver leaf is a type of fungal disease that can attack the plant.
Brittle Gum (Eucalyptus mannifera)