Most eucalyptus trees are native to Australia and its neighboring islands. The hardier species were brought from there to the warmer regions of the world from there. This has created much needed industry, as well as problems. The oil and the wood are the most useful products, but there are purposes for every part of the tree.
In areas where eucalyptus can be grown, it is an attractive landscape plant. It is tall and narrow, so it can be grown in small spaces. Some species do get very large, but the snow gum (Eucalyptus pauciflora niphophila) tops out at only 25 feet. It is one of the hardiest species and can be grown in USDA zone 7 and up. This is the most adaptable eucalyptus for the home garden. Another hardy gum is the cider gum (Eucalyptus gunnii). These trees need plenty of water and sunshine.
Eucalyptus is an important timber crop in countries like Africa and Peru. The trees grow fast and will re-grow from the roots after they are harvested. They grow so well that they can replace native vegetation at a rapid rate. This is a growing concern. Native forests have been replaced by eucalyptus for the pulp industry. The wood is also used to make furniture and musical instruments (digeridoos) and is burnt for firewood. In Australia, there are checks and balances to keep the trees contained. The leaves are eaten by koala, marsupials and opossum, and natural fires keep the trees under control.
Eucalyptus oil had been used medicinally by Australian Aborigines for centuries. It was not commercially produced until the 1800s. Eucalyptus oil is steam distilled from the leaves. The most common constituent (cineole) is taken from Eucalyptus globulus. This oil is used in disinfectants and insecticides. The oil also has anti-bacterial and anti-fungal qualities. It is used both externally and internally. The oil can become toxic if too much is ingested. It is sold as a supplement, but should only be used if it is monitored by a health professional. Children should never take eucalyptus oil internally. External use is relatively safe if not used to the extreme. In aromatherapy, it is used to calm nerves, open bronchial tubes, treat asthma and relieve congestion. A few drops of the oil can be added to a carrier oil and rubbed into the skin. This is helpful for rheumatic pain and inflammation. There is also a citrus oil obtained from Eucalyptus citriodora, and a peppermint oil from Eucalyptus piperita.
Eucalyptus trees produce interesting pom-pom like flowers. They supply nectar to beneficial pollinators, such as bees, bats, butterflies and moths. The blossoms are responsible for a very delicate honey. The seeds are only used in tree reproduction.
Eucalyptus leaves are evergreen and aromatic. They are incorporated into living and dried flower arrangements. When preserved with glycerin they remain pliable for long periods. The leaves retain their color and scent well. The floral industry uses a large quantity of eucalyptus leaves.