Queensland Blue Gum is a fast-growing Australian eucalyptus tree producing valuable timber and essential oil.
There are two recognised subspecies, one native to small parts of Victoria state, in the temperate south of Australia, the other to a much wider area extending over much of the eastern coast of the continent, from near Batemans Bay in southern New South Wales to Cooktown in tropical north Queensland. This description is limited to the latter, or more widely distributed of the two subspecies.
It attains heights of 20 to 40 m (65 to 130 ft), depending on the growing conditions, and develops a straight trunk for one-third to half the tree's height. This supports a heavily branched, rounded crown of steeply ascending branches. The bark peels off in patches leaving a mottled grey to blue-grey surface.
The leaves and flowers are typical of eucalyptus, the mature leaves being long and narrow with a pointed tip and dull green, and the flowers small with long, creamy-white stamens. The flowers bloom in small, open clusters from winter through spring and are followed by small, woody, bowl-shaped capsules containing numerous seed.
Queensland Blue Gum wood is heavy, averaging out at around 800 kgs per cubic meter (50 lbs per cubic ft) and has medium to high natural resistance to decay, making it suitable for indoor and outdoor construction.
Suitably sized logs are sawn into beams used in heavy construction, including structural timber for house-building and railway sleepers, and into planks used for flooring, outdoor decking and for making furniture and cabinets. Small diameter logs and branchwood are cut for poles, posts and turnery. It is also prized as firewood and as a source-wood for making charcoal.
The leaves yield, on steam distillation, fair quantities of Eucalyptus oil of the cineole (aka. eucalyptol) type. The oil has a wide range of uses, including as a flavouring agent in food and medicines, a disinfectant and antiseptic agent, an active ingredient in insect repellents and as a stain remover, having proven effective in removing grease, glue and dried stains from both skin and fabric.
The flowers are a major source of pollen and a moderate source of nectar for honeybees, especially during the winter months when many other plants are not in bloom. The honey is pale to medium amber in colour with a distinctive toffee or caramel flavour.
The tree has a long history of use in rehabilitating degraded land, including use as a pioneer species on tailings leftover from copper mining. It also serves as a major food tree for koalas, which eat the leaves, and is a habitat for some of Australia's native possum species.
Queensland Blue Gum grows well and produces good quality, valuable timber in a range of climates, from warm-temperate to tropical and from sub-humid to humid conditions. The climate in its native range is characterised by annual lows of 9 to 25 °C, annual highs of 19 to 36 °C, annual rainfall of 800 to 3500 mm and a dry season of 7 months or less.
New plants are usually started from seed, which germinate readily without the need for any pre-treatment. The seed are sown in individual containers with a free-draining potting mix and the seedlings planted out when 40 cm (16 in) tall or taller, with the best result achieved when planted at the start of the rainy season.
Queensland Blue Gum performs well on clay, loam and sand soils, providing they are well-drained and of a slightly acid to slightly alkaline nature, generally with a pH of 6.0 to 7.5. Sites should have full sun exposure.
It has good tolerance to drought and seasonal flooding, but not waterlogging and is moderately salt tolerant with growth reported to be unaffected by moderately saline conditions, the equivalent of up to 3.2 grams of dissolved salt per litre of water.
The small seed are easily dispersed by wind and flowing water, enabling its spread beyond cultivation. Assessment of its weed potential is, however, conflicting. It is assessed as a low weed risk species for Hawaii but as a high weed risk species for Florida, respectively by the Hawaii Pacific Weed Risk Assessment project (HPWRA) and the IFAS Assessment of Non-Native Plants in Florida's Natural Areas.
Prolonged skin contact with Eucalyptus essential oil may cause burning dermatitis and blisters in some people and can be poisonous if ingested in large amounts.
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