What are Sydney red gums?
The Sydney red gum is a medium to tall tree species that grows in eastern Australia. Whilst not a eucalyptus tree, the Sydney red gum is placed in a larger family of trees commonly known as gum trees. Sydney red gum trees can be easily spotted due to their twisted branches and richly patterned red/orange smooth bark in summer that turns to pink/grey by winter before shedding in small scales.
Sydney red gums are also known by the name smooth-barked apples. They can often be seen growing out of cracks and crevices in sandstone around the Sydney area.
They can grow up to 30 metres tall and usually have clusters of cream flowers in November and December each year. Sydney red gum seed capsules are 13 to 15 millimetres long with five prominent ribs.
The scientific name for the Sydney red gum is Angophora costata. Angophora is derived from the Greek word meaning goblet or vessel, whilst costata is Latin for ribbed. The name Angophora costata describes the ribbed fruit or nut of the Sydney red gum.
Angophora costata was given the common name of Sydney red gum because its gooey sap or gum is bright red. It was this tree and its gum that inspired Sir Joseph Banks to call this large group of trees, including the eucalypts, gum trees.
Aboriginal Peoples from the Sydney region know the tree as kajimbourra.
Where are Sydney red gums found?
Sydney red gums can be found from the south coast of New South Wales all the way up into central Queensland. Generally they grow along the coast and ranges within this area. Most often they grow on sandy soils, particularly when those soils are formed over sandstone.
What eats Sydney red gums?
The blossoms of Sydney red gums attract many native animals such as possums, grey-headed flying foxes, lorikeets and bees who come to feed on the nectar.
What role do Sydney red gums play in the ecosystem?
Sydney red gum trees play an important role in the ecosystem. For example, the roots of these gum trees help control erosion of the loose sandy soils in which they grow. The leaves and flowers on the other hand are an important food source for a range of mammals and birds.
Sydney red gum trees can live for hundreds of years. These mature trees are especially important as they provide habitat in the form of tree hollows and hollow logs. Hollows are used as shelter by a range of native mammals, such as possums, and birds, such as owls and parrots.
It is important to protect these trees so that they can grow large and old enough to produce hollows. Many invertebrates, including spiders, will make a home in or under the bark of the Sydney red gum.
How are Sydney red gums used by Aboriginal Peoples?
Sydney red gums provide numerous resources for Darug Peoples.
The bulges on the trunk can be cut off and hollowed out to make bowls.
The red gum – yarra in Darug – can be used as an adhesive, a sweet lolly, a toothache remedy or applied directly to sores, cuts and bites. The gum can also be boiled in water and used as an antiseptic wash or consumed in dilute and small amounts to help treat diarrhoea.
How are Sydney red gums adapted to their environment?
Like many tree species in Australia, Sydney red gums are well adapted for growth in dry conditions and poor soils. These gums have hard 'sclerophyll' leaves which do not require a lot of water to grow. Their leaves are also covered in a thick waxy layer which reduces the amount of water that is lost through the surface of their leaves.
Inside the leaves are oil glands, which produce a toxic oil which makes most animals sick when eaten. It is important to ward off herbivores as replacing eaten leaves is difficult when there isn’t much water or nutrients available in the environment.
As part of the Australian landscape, Sydney red gums are also well adapted to fire. After fire, leaves resprout from special ‘back up’ buds, called epicormic buds, found beneath the bark of the trunk and also from their lignotuber, a woody swelling at the base of the tree.
Also, after fire, this gum tree drops its seeds to the ground so that they can germinate in ash-rich soil clear from other plants which would otherwise compete for sunlight and water.
