TASMANIA'S FLORAL EMBLEM
THE MAJESTIC BLUE GUM

Eucalyptus globulus ssp. globulus (Myrtaceae)

Eucalyptus globulus ssp. globulus
This old Tasmanian blue gum (Eucalyptus globulus ssp globulus) is the oldest tree in the gardens. It is all that is left of
the blue gum woodland which grew here prior to the establishment of a large market garden by John Hangan in 1806 and subsequent development of the Royal Tasmanian Botanical Gardens in Hobart.

A SAD FOOTNOTE:   On 19 August, 2006 the Royal Tasmanian Botanical Gardens announced that this tree has to be
removed as it poses a threat to visitors. The 27 metre high tree has been severely weakened from fungal rot and damage by a probable lightning strike and, with its spreading canopy that acts as a large sail in windy conditions, there is a risk of falling limbs.  The decision was made with deep regret.

This was the first hardwood forest tree to have its chloroplast genome sequenced and when the DNA analysis was completed, clones of the tree were produced by the University of Tasmania, one of which has been planted on the RTBG Eucalyptus Lawn.  All timber from the tree will be retained by the gardens and depending on its condition and
the extent of the fungal damage, it may be used for specialist craft projects.


E. globulus flowers
   Photo courtesy Launceston Field Naturalists Club
E.globulus juvenile leaves

E. globulus bark

The tree has a skirt of rough bark, which is smooth, yellowish  or greyish  on the upper trunk and limbs after decorticating above in long strips.  Easily identified by its very large blue-green glaucous juvenile leaves on square stems, its large, up to 30 cm long, dark green sickle-shaped adult leaves, smelling strongly of eucalyptus, and the large blue-green 4 ribbed capsule 2 cm across, covered with white waxy bloom. The flower is large, 15-20 mm across, solitary or 3 together in the leaf axils.  Flowering spring-summer.

A useful and versatile tree, the heartwood is light yellowish brown with open-textured grain; commonly interlocked, distinct growth rings, strong, moderately durable and used for light and heavy construction, poles, piles and railway sleepers.

Notes:

Sclerophyll - a leathery or hard leaf with thick cuticle, hence shrubs and trees with such hard, tough or small stiff leaves.

The botanical name globulus (a little button) refers to the operculum - a cap which separates along a circular line of unripened fruits.


E. globulus bark pattern


Eucalyptus globulus seed capsule  



Like the Oak tree in Britain or the Baobab in South Africa, the Blue Gum is a source of food, shelter and accommodation for a wide variety of wildlife.  Silvereyes and fantails use the height to launch into feeding forays. Wattlebirds use it as a noisy battlefield area for important territorial decisions, as well as upmarket dining during the flowering season where they are joined by Rosellas and Swift parrots. The large Yellow-tailed Black Cockatoos hunt assiduously for borer grubs in the boughs, which they listen for and then extricate. The damage sometimes looks serious, but the damage by borers (larvae of a large moth) is worse and the trees survive.  All honeyeaters need it for nectar, pollen and insects, particularly at breeding time. In winter the Yellow-throated Honeyeater, which is endemic to Tasmania, searches beneath the loose bark strips to vacuum up insect larvae, making quite an audible rustling sound.  The Currawong, a noted pragmatist and snapper-up of unconsidered trifles, (e.g. nestlings, lizards, spiders, frogs, grubs and barbecue scraps) will do the same.    Even tiger snakes are known to use large fallen branches on the ground for sun-bathing, as a handy alternative to poa grass cushions or warm lichen-covered rocks. 

Mammals that typically live in Blue Gums are Brush and Ring-tailed possums, which feed on leaves and flowers and rely on old trees for sleeping and nesting cavities. Certain small members of the kangaroo family such as Bettongs find species of fungi associated with the roots of eucalypts, whilst another, Potoroos, dig for insects and invertebrates in the leaf litter.







Kookaburras, working on the principle of "the One Above sees all", find the boughs a perfect place to survey prospects for the next meal or guarding hollows for nesting sites.

Kookaburra
References Native Trees of Tasmania, J.B. Kirkpatrick and Sue Backhouse
Forest Trees of Tasmania Field Guide

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