Eucalyptus globulus, commonly known as southern blue gum, is a species of tall, evergreen tree endemic to southeastern Australia. It has mostly smooth bark, juvenile leaves that are whitish and waxy on the lower surface, glossy green, lance-shaped adult leaves,, ribbed flower buds arranged singly or in groups of three or seven in leaf s, white flowers and woody fruit. There are four subspecies, each with a different distribution, occurring in New South Wales, Victoria and Tasmania.
Description
Eucalyptus globulus is a tree that typically grows to a height of but may sometimes only be a stunted shrub, or alternatively under ideal conditions can grow as tall as, and forms a lignotuber. The bark is usually smooth, white to cream-coloured but there are sometimes slabs of persistent, unshed bark at the base. Young plants, often several metres tall, and coppice regrowth have stems that are more or less square in cross-section with a prominent wing on each corner. Juvenile leaves are mostly arranged in opposite pairs, sessile, elliptic to egg-shaped, up to long and wide. Adult leaves are arranged alternately, the same glossy to dark green on both sides, lance-shaped or curved, long and wide on a petiole long. The flower buds are arranged singly or in groups of three or seven in leaf axils, sometimes sessile or on a short thick peduncle. The individual buds are also usually sessile, sometimes on a pedicel up to long. Mature buds are top-shaped to conical, glaucous or green, with a flattened hemispherical, warty operculum with a central knob. Flowering time varies with subspecies and distribution but the flowers are always white. The fruit is a woody conical or hemispherical capsule with the valves close to rim level.
Taxonomy and naming
Eucalyptus globulus was first formally described in 1800 by the French botanist Jacques Labillardière in his book, Relation du Voyage à la Recherche de la Pérouse. Labillardière collected specimens at Recherche Bay during the d'Entrecasteaux expedition in 1792. The d'Entrecasteaux expedition made immediate use of the species when they discovered it, the timber being used to improve their oared boats. The Tasmanian blue gum was proclaimed as the floral emblem of Tasmania on 27 November 1962. The species name is from the Latinglobulus, a little ball or small sphere, referring to the shape of the fruit. In 1974, James Barrie Kirkpatrick described four subspecies and the names have been accepted by the Australian Plant Census. Each subspecies has a characteristic arrangement of its flower buds:
Eucalyptus globulus subsp. bicostata J.B.Kirkp., commonly known as southern blue gum, eurabbie, blue gum or Victorian blue gum has sessile flower buds arranged in groups of three;
Eucalyptus globulus Labill. subsp. globulus, commonly known as Tasmanian blue gum, southern blue gum or blue gum has flower buds arranged singly in leaf axils;
Eucalyptus globulus subsp. maidenii J.B.Kirkp., commonly known as Maiden's gum has flower buds arranged in groups of seven;
Eucalyptus globulus subsp. ''pseudoglobulus J.B.Kirkp., commonly known as Victorian eurabbie has pedicellate flower buds arranged in groups of three.
Distribution and habitat
Blue gum grows in forests in New South Wales, Victoria and Tasmania, including some of the Bass Strait Islands. Subspecies bicostata occurs in montane and tableland areas between the Carrai Plateau in northern New South Wales and the Pyrenees in Victoria. Subspecies globulus is mainly found in lowland parts of Tasmania, but is also found on some Bass Strait islands including King Island, and in the extreme south-west of Victoria. Subspecies maidenii occurs on near-coastal ranges of south-eastern New South Wales and eastern Victoria. Subspecies pseudoglobulus is mostly distributed in eastern Gippsland but there are isolated populations further inland and in the Nadgee Nature Reserve in south-eastern New South Wales. There are naturalised non-native occurrences in Spain and Portugal, and other parts of southern Europe incl. Cyprus, southern Africa, New Zealand, western United States, Hawaii, Macaronesia.
Unusual specimens
They typically grow from tall. The tallest currently known specimen in Tasmania is tall. There are historical claims of even taller trees, the tallest being.
Plantations
Blue gum is one of the most extensively planted eucalypts. Its rapid growth and adaptability to a range of conditions is responsible for its popularity. It is especially well-suited to countries with a Mediterranean-type climate, but also grows well in high altitudes in the tropics. It comprises 65% of all plantationhardwood in Australia with approximately planted. In about 1860 Francis Cook planted the tree on Monserrate Palace, his property at Sintra in Portugal and within twenty years it had attained the height of 100 m and a circumference of 5 m. By 1878 the tree ″had spread from one end of Portugal to the other″. In 1878 the tree was also planted, partly on Cook's recommendation, in Galway, Ireland to reclaim ″useless bog land″. E. globulus begun to be planted as plantations in Los Lagos and Los Ríos regions of Chile in the 1990s. However at these latitudes around the 40th parallel south the tree is at the southern border of the climatic conditions where it can grow, hence good growth in this part of southern Chile requires good site selection such as sunny north-facing slopes. Some of these plantations grow on red clay soil.
Uses
Timber
Blue gum timber is yellow-brown, fairly heavy, with an interlocked grain, and is difficult to season. It has poor lumber qualities due to growth stress problems, but can be used in construction, fence posts and poles.
Pulpwood
Essential oil
The leaves are steam distilled to extract eucalyptus oil. E. globulus is the primary source of global eucalyptus oil production, with China being the largest commercial producer. The oil has therapeutic, perfumery, flavoring, antimicrobial and biopesticide properties. Oil yield ranges from 1.0-2.4%, with cineole being the major isolate. E. globulus oil has established itself internationally because it is virtually phellandrene free, a necessary characteristic for internal pharmaceutical use. In 1870, Cloez identified and ascribed the name "eucalyptol" — now more often called cineole — to the dominant portion of E. globulus oil.
Herb tea
Tasmanian blue gum leaves are used as a herbal tea.
Honey
Blue gum flowers are considered a good source of nectar and pollen for bees.
