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Eucalyptus globulus subspecies globulus

Brian Walters

Eucalyptus globulus subsp. globulus is one of the most widely cultivated of Australia's native trees. It can be found in parks and gardens in many parts of Australia and is well established overseas (eg. Algeria, Brazil, France, India, Spain and Portugal). In California it is so well known that many regard it as a native Californian species. Although it is Tasmania's floral emblem and is commonly known as the Tasmanian blue gum, it occurs naturally in other parts of Australia.

It is a medium to very tall forest tree which may reach 70 metres in ideal conditions but is more commonly 15-25 metres in height. In very harsh and exposed conditions it can adopt a shrubby habit. It is popular in cultivation, particularly for its attractive, blue-grey (glaucous) juvenile foliage and fast growth. However, it is really too large for normal-sized suburban blocks and it has a strong and vigorous root system which can cause damage to buildings and underground pipes if the plant is not properly located.

Eucalyptus globulus
The Tasmanian Blue Gum, Eucalyptus globulus is found naturally in New South Wales and Victoria as well as in Tasmania. Select the thumbnail image or highlighted phrase for a higher resolution image (52k). Photo: Bruce Champion

The tree has a rough, greyish bark at the base but sheds the bark on the upper trunk and branches in long ribbons. The white flowers usually occur singly in the leaf axils in spring and early summer. They are followed by greyish, 4 or 5-valved fruits ("gum nuts") about 20 mm in diameter.


Distribution and Forms

E.globulus subsp. globulus is a common tree which can be found in eastern and south-eastern Tasmania, as well as in the islands of Bass Strait. It also occurs in southern Victoria (the Otway Ranges and Wilson's Promontory). It can be found from sea level up to about 450 metres.

Distribution Map

Apart from E.globulus subsp. globulus, there are three other sub-species which differ from the Tasmanian blue gum in a range of characteristics including bark , habit and flower arrangement:

  • Maiden's gum - E.globulus subsp. maidenii; found in south-east New South Wales and north-east Victoria; flowers in groups of 7 in the leaf axils; bark usually shed to base.

  • Gippsland blue gum - E.globulus subsp. pseudoglobulus; found in the far south-east of New South Wales, eastern and southern Victoria and Flinders Island in Bass Strait; flowers mainly in groups of 3 in the leaf axils; bark usually shed to base.

  • Southern blue gum - E.globulus subsp. bicostata; found in a number of locations along the Great Dividing Range from northern New South Wales to western Victoria; flowers mainly in groups of 3 in the leaf axils; rough bark usually retained at base.

Commercial Uses

E.globulus subsp. globulus has an open textured wood with distinct growth rings. The timber is strong and durable and has been used for a variety of purposes including railway sleepers, piles, paper making, oil and honey. The tree coppices well and has been used for fuel.

In earlier days the timber had uses in shipbuilding:

"One such, built at Geeveston in the 1870s for a Dunedin Scot, was of blue gum with Huon pine top sides and the Otago Times described her as 'the most sightly ship ever seen in these waters'".
Alexander Rule, Forests of Australia.

The volatile oil content of E.globulus is relatively low but that hasn't prevented substantial oil harvesting from the species, particularly in Spain and Portugal. The oil is pale yellow in colour and is used in perfumery and in soap making.


...in the eye of the beholder!

Not everyone loves the blue gum.

In California it is loved by some and loathed by others. The tree was introduced in the mid 1800s and was promoted as a wonder of nature, able to cure disease and purify the air. However, the major stimulus for it's widespread planting resulted from the California gold rush and the devastation that this wrought on the native vegetation. During this boom period, the plant was promoted for all sorts of money-making ventures, some of which succeeded but many failed when, by the early 1900s, commercial use of blue gum was generally abandoned.

The tree by this time had become well entrenched in it's new home and, without the natural predators found in eastern Australia, it spread into areas of natural vegetation and replaced native Californian species. Today it is listed among the exotic pest plants of greatest concern by the California Exotic Pest Plant Council.

Despite these problems there are many who view the blue gum as a significant contributor to California's planted environment. Here is a selection of comments that were posted to the internet mailing list "Medit-Plants" on this topic:

".... Eucalyptus were originally imported to be grown for lumber for railroad ties when the railroads were being built in California. Turns out the kind that were imported were the wrong kind, and were not able to be used..... Eucalyptus have been used extensively for windbreaks in agricultural areas, and have grown well".

"...even though Eucalyptus is not a California native, I think that they are so much a part of the landscape that I couldn't imagine living here without them. I have read that their narrow, pendulous leaves condense fog and remove significant moisture from the atmosphere that way, troubling native species that depend on getting their water from the air. But that's the only bad thing I can say about them."

"I wouldn't say that Eucalyptus are unwanted.....the trees are the signature of the community and are incredibly beautiful so long as they don't drop branches on your head.....It is a great windbreak and provides wonderful shade on hot days."

"The trees are certainly very vigorous. In some areas they are a fire hazard. Eucalypts were blamed in part for the massive house-consuming fire in Oakland several years back. In some areas they have run wild, producing dense groves of trees that crowd out everything else.......One spot that's definitely not an eyesore is an old Eucalyptus grove, originally part of a failed timber venture, along Interstate 5 in Central California. It has now been turned into a highway rest stop and it's the shadiest place for twenty miles. Very nice."


References

  • Boland, D, Brooker, M, Chippendale, G, Hall, N, Hyland, B, Johnston, R, Kleinig, D and Turner, J (1984), Forest Trees of Australia, Thomas Nelson, Australia and CSIRO.
  • Brooker, M and Kleinig, D (1990; Revised Ed.), Field Guide to the Eucalypts, Vol.1 South-eastern Australia, Inkata Press, Melbourne and Sydney.
  • Elliot, R and Jones D (1986), The Encyclopaedia of Australian Plants, Vol.4, Lothian Publishing Company Pty Ltd, Melbourne.
  • Heyman, H (1995); Blue Gum Fever, Pacific Horticulture 56 (3) 1995.
  • Rule, A (1967); Forests of Australia, Angus and Robertson.




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Australian Plants online - March 1998
The Society for Growing Australian Plants