Sugar Gum

''Eucalyptus cladocalyx'', commonly known as sugar gum, is a species of eucalypt tree found in the Australian state of South Australia. It is found naturally in three distinct populations - in the Flinders Ranges, Eyre Peninsula and on Kangaroo Island.

Description

The tree notable for its mottled colourful yellow to orange bark, strongly discolourous leaves and inflorescences grouped on leafless branchlets inside the tree crown. The old bark is smooth and grey, shedding in irregular patches to expose the fresh yellowy-brown bark. Flowers are creamy-white in summer. The capsules are barrel to urn shaped.

Sugar gums from the Flinders Ranges reach up to in height and have the classic "gum" habit - with a straight trunk having a diameter at breast height (dbh) of and steep branches occurring about halfway up. Each main branch ends with its own little canopy. They are commonly cultivated as farm windbreaks and for timber. However, Eyre Peninsula and Kangaroo Island trees are much shorter, typically between in height, and often have crooked trunks and a dbh of . The crown has an open spreading habit with a typical spread of .

The strongly discolorous, glossy adult leaves are arranged alternately supported on a petiole that is in length. The leaf blade is darker green on upper side and paler below with slightly falcate to lanceolate shape, a length of and a width of , with a base usually tapering to the petiole. The side-veins in the leaf are at an acute or wider angle and densely reticulate. The intramarginal vein is parallel to but removed from margin, with small and obscure oil glands.

It flowers in summer, producing white-cream-yellow flowers. The axillary unbranched inflorescence occur in groups of buds 7, 9 or 11 buds per umbel. The oblong pale green, yellow to creamy mature buds have a length of and a width of . The buds are often longitudinally striated and scarred, with a rounded operculum, inflexed stamens and cuboid to oblong anthers. The urceolate or barrel-shaped, longitudinally ribbed fruits that form after flowering are in length and wide, with a descending disc and three or four enclosed valves. The light grey to brown seeds within the fruit have a flattened-ovoid shape that can be pointed at one end and are long.

Taxonomy

The species was first formally described by the botanist Ferdinand von Mueller in 1853 in the journal ''Linnaea: Ein Journal für die Botanik in ihrem ganzen Umfange, oder Beiträge zur Pflanzenkunde''.

In 1860, von Mueller referred to ''Eucalyptus corynocalyx'' in '' Fragmenta phytographiae Australiae'', citing several earlier publications, including the ''Linnaea'' journal article, but all only have a description of ''E. cladocalyx''. ''Eucalyptus corynocalyx'' is therefore a nomen illegitimum and a synonym of ''E. cladocalyx''.

The specific epithet is taken from the Ancient Greek words ''klados'', meaning ''branch'', "twig" or "stem" and ''kalyx'', meaning "cup", "cover" or "outer envelope of a flower", in reference to the leafless branchlets that bear the flowers.

In 2013, Dean Nicolle describe three subspecies of ''E. cladocalyx'' and the names have been accepted by the Australian Plant Census:
* ''Eucalyptus cladocalyx'' F.Muell. subsp. ''cladocalyx'' is a lower-growing, more spreading tree than the other subspecies and has short, broad leaves and larger fruit;
* ''Eucalyptus cladocalyx'' subsp. ''crassa'' D.Nicolle is the tallest-growing subspecies and has long, narrow leaves and large fruit;
* ''Eucalyptus cladocalyx'' subsp. ''petila'' D.Nicolle is a tall subspecies with erect branches, narrow adult leaves and relatively small fruit.

Distribution

''Eucalyptus cladocalyx'' is endemic to southern parts of South Australia. It is found in three distinct populations: in the southern and central-eastern parts of the Eyre Peninsula, through much of the Flinders Ranges, and on Kangaroo Island. It is most likely part of relic forests of wetter climates from the past.

''E. cladocalx'' has now become naturalised in the South West region of Western Australia, in southern Victoria and, beyond its native range, in some parts of south-eastern South Australia. It is also naturalised overseas in northern and southern Africa, in California, Hawaii, Arizona, Israel, Chile, Greece, Portugal and Spain.

Subspecies ''cladocalyx'' is restricted to the southern and eastern Eyre Peninsula, subspecies ''crassa'' to Kangaroo Island and subspecies ''petila'' to the southern Flinders Ranges.

Uses

The tree has been widely planted across southern Australia, often as a windbreak or shelterbelt, but also for timber and firewood production. The wood is termite resistant, with moderate strength and durability, and can be used for furniture, flooring, posts, construction timber and railway sleepers.

It is a fast-growing tree but is best planted in open sun in clay, loam or sandy soils. It is an efficient user of water and drought and frost tolerant, with flowers that attract bees. It is also known to be a suitable breeding habitat for the Yellow-tailed Black-Cockatoo.

''E. cladocalyx'' is well adapted to regular bushfires and can resprout epicormically. It also produces a large number of seedlings through wind dispersal of seeds.

The hard and heavy heartwood is a pale yellow-brown colour and has fine uniform texture with an interlocked grain. The density of air-dried wood is around and is moderately durable.

The dwarf subspecies ''cladocalyx'' is sold in the nursery trade as ''E. cladocalyx'' 'Nana'.

Weed potential

''E. cladocalyx'' has invaded bushland in Western Australian, where it has been introduced. It has the capacity to spread up to 70 metres away from locations where it has been planted, and seems to survive bush fires more effectively than several local eucalypt species. It has become an invasive species in South Africa, where it is now registered as a category 2 invader plant.

References

* Holliday, I. ''A field guide to Australian trees (3rd edition)'', Reed New Holland, 2002
* Cronin, L. ''Key Guide to Australian Trees'', Envirobook, 2000

Rawlings, M. ''Regional allozyme divergence in Sugar Gum, Eucalyptus cladocalyx'', 2005, Centre for Plant Biodiversity Research

{{DEFAULTSORT:Eucalyptus cladocalyx
Trees of Australia
Trees of Mediterranean climate
cladocalyx
Flora of South Australia
Myrtales of Australia
Plants described in 1853
Taxa named by Ferdinand von Mueller