Corymbia maculata (syn. Eucalyptus maculata), commonly known as Spotted Gum, is a gum tree endemic to Queensland, New South Wales and Victoria. It belongs to Family Myrtaceae. It occurs on infertile and dry sites of shales and slates.

Spotted Gum is a tall tree with a straight trunk, growing up to 45 metres in height. Spotted Gum has smooth powdery bark which is white, grey or pink; often with characteristic patches (‘spots’). The name maculata is derived from the Latin word maculosus, meaning ‘spotted’. The bark is shed in polygonal flakes.

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Five Spot Gum trees planted in Royal Botanical Garden, Sydney
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A label on the Spotted Gum tree
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The tree in the right at a height of about 2 to 3 metres is equipped with a dendrometer, a data reader gathering information on tree growth rates.
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Smooth powdery bark which is white, grey; often with characteristic patches (‘spots’)

 

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Details of the characteristic patches (‘spots’)

The adult leaves are lanceolate (shaped like a lance head; of a narrow oval shape tapering to a point at each end.) They are about 10 to 21 cm long and 1.5 to 3 cm wide.

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The leaves of Spotted Gum are lanceolate in shape
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Leaf venation and oil glands in a fresh leaf viewed with transmitted light. The yellow white structure in the middle is the midrib.
Details of the above image
Details of the above image

 

The genus Corymbia is named from the Latin corymbium; a ‘corymb’ refers to the form of the flower clusters.

Spotted Gum has small, white flowers occur from late autumn to spring. The flowers are in panicles with umbels of 3, some are in umbels of 2. They are known as umbellasters of 3 or 2 flowers. The pedicel of the flower is very short, 3-6 mm long and cylindrical.  The operculum (bud cap or calyptra) is hemispherical and shorter than the hypanthium. The stamens are numerous and white in colour. There are carpels in the ovary.

 

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Flower buds are in panicles with umbels of 3, some are in umbels of 2.
More samples of umbels in groups of 3 and 2.
More samples of umbels in groups of 3 and 2

 

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The flower bud still has its operculum (bud cap). The operculum is semicircular in shape. Below the operculum is the hypanthium.
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The operculum has been removed to show the coiled up stamens
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The flower bud has been cut sagitally into halves. The operculum is still partially attached onto the flower bud. The stamens are coiled up in an orderly manner.

 

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The stamens are made up of long white filaments and yellowish white anthers. The pistil is in the middle. The stigma is pale green in colour.
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The ovary has been cut transversely to show the three carpels inside.

 

The fruit is ovoid or slightly urceolate (urn shaped with a swollen middle and a narrow top) in shape. Most Corymbia species have thick-walled woody fruit that are more or less urn-shaped. The dimensions of the fruit are about 10–14 mm long, 9–11 mm in diameter; disc depressed; valves enclosed.

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Three fruits of the tree, the one on the left is younger as the colour is still green whereas the other two are older.
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The fruit is ovoid or slightly urceolate in shape

 

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The development of a flower bud to a flower and eventually into a fruit

 

The species is often used for planting in parks and as a street tree, however its mature size makes it unsuitable for most home backyards.

The hard and durable timber is utilised for a number of purposes including poles, posts, construction timber, panelling, joinery, tool handles, furniture, plywood, firewood and charcoal.

 

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The dendrometer is a data reader which gathers information on tree growth rates. This is a joint project of researchers from University of Melbourne and the Royal Botanic Garden, Sydney.

Botanical Drawing

Edward Minchen 1897
Eucalyptus maculata by Edward Minchen from: ‘The Flowering Plants and Ferns of New South Wales – Part 6’ (1897), J H Maiden

 

Bibliography

https://en.wikipedia.org/wiki/Corymbia_maculata

http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Corymbia~maculata

https://www.florabank.org.au/lucid/key/Species%20Navigator/Media/Html/Corymbia_maculata.htm

 

 

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