Eucalyptus (Eucalyptus)

Eucalyptus is a genus of diverse flowering trees or shrubs from the myrtle family (Myrtaceae). Species of these plants are found predominantly in Australia, where there are around 700 known species of Eucalyptus. Most originate from Australia, with very small numbers of plants found in adjacent parts of New Guinea and Indonesia, or the Philippine islands.

Eucalyptus species are cultivated throughout the tropics and subtropics, including the Americas, England, Africa, the Mediterranean, the Middle East, China and the Indian subcontinent.

Eucalyptus is one of three similar plant genera commonly referred to as "eucalypts", the others being Corymbia and Angophora. Many are also called gum trees, as they are characterized by large amounts of sap when the bark is damaged. The name eucalyptus comes from Greek: εὐκάλυπτος - eukályptos, meaning "well covered". Eucalyptus has very smooth, often silky glossy bark that can be white, cream, grey, green or copper.

Since global development, Eucalyptus has attracted the attention of researchers and ecologists. Both as a fast-growing source of timber, or for its oil, which can be used as a cleaner and also works as a natural insecticide (pest control agent). Eucalypts draw huge amounts of water from the soil. In their homeland, eucalyptus was planted to drain swamps, thereby reducing the risk of malaria. They are also planted as windbreaks and for soil erosion control.

Eucalypts can be shrubs or very tall trees.

Small - up to 10 metres in height

Medium - 10 to 30 metres

Tall - 30 - 60 metres

Very tall - over 60 metres

Nearly all Eucalypts are deciduous trees, only some tropical species shed their leaves at the end of the dry season. As with other members of the Myrtaceae family, Eucalyptus leaves are covered with oil glands. Eucalypts producing abundant oils are therefore an important part of the genus. The leaves of mature Eucalyptus plants are usually lanceolate, petiolate, and waxy or glossy green. But there are many exceptions to this pattern (e.g. E. melanophloia, E. melanophloia, E. setosa).

Most characteristic Eucalyptus species have typical flowers and fruits (capsules). The flowers have numerous striking stamens that can be white, cream, yellow, pink or red. The name Eucalyptus, from the Greek words eu-, well, and kaluptos, covered, meaning "well-covered", describes the cap that covers the stamens. The capsules are roughly cone-shaped and have valves at the end that open to release the seeds.

The appearance of Eucalyptus bark changes with the age of the plant, the length of bark fibres, the degree of wrinkling, thickness, hardness and colour. All mature eucalyptus trees add an annual layer of bark, which contributes to a larger trunk diameter. In some species, the outermost layer dies and forms either long strips (as in Eucalyptus sheathiana), large flakes (E. diversicolor, E. cosmophylla, E. cladocalyx). The bark surface can be matt (E. cosmophylla), glossy or satin.

There are more than 700 species of Eucalyptus. Some of them differ from the mainstream of the genus to the extent that they are genetically completely isolated and may have only a few relatively unchanging characteristics. Most, however, can be considered as belonging to large or small groups of related species that are often in geographical contact. Some species are relatively genetically stable, while others have diverged considerably from their closest relatives.

A small genus of similar trees, Angophora, has been known since the 18th century. In 1995, new evidence, primarily genetic, showed that some Eucalyptus species were actually more closely related to Angophora than to other eucalyptus trees, and were split off into the new genus Corymbia. Although the plant genera are thus separated, some hybrids remain designated as Eucalyptus-Angophora, Corymbia and Eucalyptus, as "Eucalypts".

Several Eucalyptus species are among the tallest trees in the world. The Australian Mountain Ash is the tallest of all flowering plants (angiosperms), measuring 99.6 metres. Six eucalyptus species reach the greatest heights: Eucalyptus obliqua, Eucalyptus delegatensis, Eucalyptus diversicolor, Eucalyptus nitens, Eucalyptus globulus and Eucalyptus viminalis, over 80 m.

Most Eucalyptus species are not very frost-hardy, tolerating light frosts around -3°C. The most hardy is Eucalyptus pauciflora, which can withstand cold and frost down to -20°C. Several other species, particularly from the highland plateaus and mountains of central Tasmania, such as Eucalyptus coccifera, Eucalyptus subcrenulata and Eucalyptus gunnii, have produced hardy seed forms obtained from these genetically resistant strains. Lemon Eucalyptus tolerates temperature drops down to -5°C, yet it is better to grow it indoors for its aromatic and disinfectant properties.

Essential oil obtained from the leaves of eucalyptus plants contains compounds that are powerful natural disinfectants and can be toxic in large quantities. However, several herbivorous marsupials, particularly koalas and some possums, are quite tolerant of this fact. In koalas, these compounds are the most important factor in leaf selection. The plant's flowers produce large amounts of nectar, thereby providing food for many pollinators, including insects, birds, bats and possums.

Eucalyptus oil is easily steam distilled from the leaves and can be used for cleaning, deodorising effects and of course in the food and pharmaceutical industry, especially to support the respiratory tract. It is also used as a natural repellent against moths and mosquitoes.

High-quality honey is obtained from the nectar of some eucalyptus species. Eucalyptus wood is also commonly used to make didgeridoos, the traditional Australian wind instrument.

All parts of eucalyptus can be used to produce dyes, primarily for silk and wool. The colours that can be achieved range from yellow and orange through green, light brown to chocolate. The remaining material after processing can be safely used as compost or fertiliser.