Eucalyptus haemastoma, commonly known as Scribbly Gum, is a medium size Australian eucalypt that can grow up to about 15 m. It belongs to Family Myrtaceae. Eucalyptus haemastoma is found in dry sclerophyll woodland on the coastal plains and hills in the Sydney Region. It grows well in shallow infertile sandy soil.

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A street tree of Eucalyptus haemastoma in a Sydney suburb

The bark of the lower part of the tree is dark brown, fibrous-flaky. It is only persistent on lower trunk (a few metres only). After the shedding of the bark in short ribbons, the tree trunk and the branches are smooth with scribbles, white, grey or yellow.

The common name ‘Scribbly Gum’ is a reference to the ‘scribbles’ left on the trunk from the feeding larvae of the scribbly gum moth (Ogmograptis scribula). Eggs are laid between layers of old and new bark. The larvae burrow tunnels into the new bark and, as the old bark falls away, the trails are revealed. The diameters of the tunnels increase as the larvae grow, and the ends of the tracks are where the larvae stopped to pupate.

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Some dark brown bark still stays on the lower part of the tree trunk. Most of those dark brown bark has shed leaving the trunk pale grey, white and pale yellow.

 

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‘Scribbles’ left on the trunk from the feeding larvae of the scribbly gum moth
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More groups of ‘scribbles’ left on the trunk

The adult leaves are stalked, lanceolate to broad-lanceolate or curved, 12 – 17 cm long, 1.5 – 4 cm wide, green or grey-green, glossy. The leaves contains a lot of oil glands.

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The adult leaves are stalked, lanceolate to broad-lanceolate or curved,. The colour of the upper and lower epidermis is grey green and similar

 

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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
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Details of the above image

 

The flowers are in clusters of 11 or more. Flower buds are ovoid or clavate, 6-8 mm long, 4-5 mm in diameter. Operculum (calyptra or bud cap) is hemispherical or shorter and narrower than hypanthium.

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This inflorescence or cluster contains 14 flower buds
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The flower bud with the operculum has been sagittally cut in halves to show the arrangement of the stamens
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The operculum is about to detach from the flower bud exposing the white stramens inside
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The flower bud without the operculum is cut sagittally into halves to show the white stamens and the green style

The white flowers appear from mid autumn to late winter (April to August) in Sydney.

The conspicuous part of the flowers are the white filaments of the stamens. The style is green in colour.

The flower does not have petals or sepals, instead it has a hypanthium. The ovary commonly has 4 carpels (4-locular ovary).

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The flower in full bloom

 

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The flower has been sagittally cut into halves. The stamens in the centre of the flowers have their anthers pointing downwards. The style is not too long and is green in colour. Large ovules in the ovary.
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The ovary has been cut open to show the 4 carpels with ovules inside.

After fertilisation, the ovules develop into seeds and the ovary develops into fruit (gum nut).

The fruit is conical or pyriform in shape, 6–9 mm long, 6–9 mm in diameter; the disc is slightly raised; the valves are on rim-level.

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The fruit is conical or pyriform in shape, 4 valves
Diagram of a fruit
Diagram of a fruit
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The detail of the top part of the fruit showing the 4 valves
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The disc is slightly raised
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The development of the flower bud to flower and finally to fruit

 

Acknowledgements

I would like to thank Mr Andrew Orme of the National Herbarium of New South Wales (Royal Botanic Garden) for his help in identifying the tree.

 

Bibliography

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

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

http://www.hornsby.nsw.gov.au/media/documents/environment-and-waste/bushland-and-biodiversity/native-tree-database-fact-sheets/Fact-sheet-Eucalyptus-haemastoma-Broad-leaved-Scribbly-Gum.pdf

 

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