Sydney red gum fact sheet – kajimbourra | Field of Mars EEC

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 branching twisted branches and richly patterned pink or orange smooth bark, often with pink-grey patches. They can often be seen growing out of cracks and crevices in sandstone around the Sydney area.

Sydney red gum trees in a forest with smooth orange bark and twisted branching trunks.

Sydney red gums growing in Lane Cove National Park

Fast facts – Sydney red gum

Scientific name – Angophora costata – Angophora from Greek for “goblet or vessel” and costata from Latin for “ribbed”, describing the ribbed seed capsules.

Appearance – Medium to tall tree (up to 30m) with twisted branching limbs and richly patterned pink or orange smooth bark with pink-grey patches.

Where it grows – Found from the NSW south coast to central Queensland, mostly along the coast and ranges, often on sandy soils over sandstone and even from cracks in sandstone rock.

Pollinators and visitors – Clusters of cream flowers in November and December; it sheds bark in summer in irregular pieces. Long-lived trees (hundreds of years) that provide hollows and fallen logs used by possums, kookaburras, owls, parrots and many other animals.

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. Sydney red gum seed capsules are 13 to 15 millimetres long with five prominent ribs. The ribs distinguish them from the seed pods of eucalypt trees. The leaves grow in an opposite formation along the stems, which also distinguishes Sydeny red gums from eucalypts.

Sydney red gums are also known by the name smooth-barked apples. They can grow up to 30 metres tall and usually have clusters of cream flowers in November and December each year. They shed their bark in summer in irregular shaped pieces.

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.

Close-up of a Sydney red gum trunk showing smooth pink and grey mottled bark.

Sydney red gum trunks and branches are usually pink or orange with grey patches.

Woody Sydney red gum seed pods with five raised ribs along their sides.

The seed pods of Sydney red gums are ribbed.

Bright red Sydney red gum sap oozing from a trunk with pieces of shed bark on the ground.

The sap or gum from the Sydney red gum is dark red. The bark sheds in irregular pieces.

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.

Smooth pink and grey Sydney red gum trunks growing in bushland among large sandstone rocks.

Sydney red gums often grow on sandstone.

Sydney red gum roots spreading over a sandstone rock as the tree grows from a small crack. Sydney red gums can grow in small cracks in rocks spreading their roots over the rocks for support.

What eats Sydney red gums?

The blossoms of Sydney red gums attract many native animals such as possums, grey-headed flying foxes, rainbow 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 are an important food source for a range of mammals, birds and invertebrates. Many invertebrates, including spiders, will make a home in or under the bark of the Sydney red gum. Red triangle slugs shelter in the leaf litter at the base and eat the algae on the trunk.

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 kookaburras, owls and parrots. It is important to protect these trees so that they can grow large and old enough to produce hollows.

Large old Sydney red gum with bent twisted branches and bulbous lumps that can form hollows for wildlife.

Large old Sydney red gums provide hollows for shelter and nesting.

Chain-link pattern trail left by a red triangle slug on the smooth pink trunk of a Sydney red gum. Red triangle slug trail on the trunk of a Sydney red gum

Sydney red gum leaf with irregular-shaped holes showing damage from leaf miner insects. Evidence of leaf miners that have eaten the leaves of a 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.

Because of their spreading branches, protecting the plants below them, some local Aboriginal Peoples refer to Sydney red gums as 'grandmother trees'.

The red sap, the gum – y arra in Darug – can be used as an adhesive, a sweet lolly, a toothache remedy or applied directly to sores, cuts and bites. The gum has antiseptic properties and can be boiled in water and used as an antiseptic wash or consumed in diluted and small amounts to help treat diarrhoea.

A single Sydney red gum provides many resources for Darug Peoples who have deep knowledge of its uses.

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 do not require a lot of water to grow and have hard 'sclerophyll' leaves to prevent water loss. 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 the environment is low in water and nutrients.

Large spreading Sydney red gum with bent twisted branches known as a “grandmother tree” by some Aboriginal Peoples.

The sclerophyllous leaves of a Sydney red gum growing in opposite formation

As part of the Australian landscape, Sydney red gums are also well adapted to fire. After fire, leaves re-sprout from special ‘back up’ buds, called epicormic buds, found beneath the bark of the trunk and also from their lignotuber, a woody swelling under the soil at the base of the tree.

Also, after fire, the Sydney red gum 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.

Dark green Sydney red gum leaves growing in opposite pairs along a reddish stem.