Swamp she-oak fact sheet | Field of Mars EEC

What are swamp she-oaks?

Swamp she-oaks are native Australian trees that often grow beside creeks, estuaries, wetlands and other low-lying places where fresh water and salt water can mix. Their scientific name is Casuarina glauca. They are not true oaks or pines, even though their drooping branchlets can look a little like pine needles.

Swamp she-oaks have rough grey-brown bark, long grey-green branchlets and tiny scale-like leaves around the joints of each branchlet. Female trees produce small red flowers that develop into woody cones containing winged seeds. In the Field of Mars Reserve, swamp she-oaks grow near Buffalo Creek and help create shady, quiet creekside habitat for animals.

A swamp she-oak branchlet.

Tiny scale leaves encircle the joints of swamp she-oak branchlets.

Where do swamp she-oaks grow?

Swamp she-oaks grow along the east coast of Australia, from Queensland to southern New South Wales. They are usually found near water, especially in brackish places along estuaries, coastal streams, creek banks and low floodplain areas. Brackish water is slightly salty.

In NSW, swamp she-oak is the main canopy tree in Swamp Oak Floodplain Forest, an endangered ecological community found in parts of the NSW North Coast, Sydney Basin and South East Corner bioregions. At Field of Mars Reserve, swamp she-oaks grow near Buffalo Creek, where their roots help hold creek banks together.

Swamp she-oak roots help stabilise sandy and muddy creek banks.

How are swamp she-oaks used by Aboriginal Peoples?

Some Aboriginal Peoples in parts of Australia used the hard wood of she-oaks, including Casuarina and Allocasuarina species, to make objects such as clubs and boomerangs. This is a broad plant-use example and should not be read as meaning that all Aboriginal Peoples used swamp she-oaks in the same way.

Local cultural knowledge shared with Field of Mars EEC by Sydney D’harawal Saltwater Knowledge Keeper Shannon Foster describes swamp she-oaks as “babysitter trees”. Their shade, open ground layer and soft carpet of fallen branchlets could create a place where children could rest and be watched nearby while adults worked.

The breeze moving through swamp she-oak branchlets also creates a soft, whispering sound. This local story reminds students that plants can be important for practical, ecological and cultural reasons. This knowledge should be shared with care, acknowledgement and respect for the knowledge holders and Country it comes from.

Swamp she-oak leaf litter can form a soft open ground layer beneath the trees.

What animals use swamp she-oaks?

Many animals use swamp she-oaks for food, shelter or nesting. Insects visit the flowers and pollen, while insect-eating birds hunt among the branchlets. Crimson rosellas, red-browed finches, yellow-tailed black cockatoos and sometimes glossy black cockatoos may feed on the seeds inside or around the woody cones.

Small mammals such as long-nosed bandicoots forage in the soil and leaf litter around swamp she-oaks. At Field of Mars Reserve, bandicoot snout pokes are often seen near the base of these trees. Birds such as willy wagtails, magpie-larks and butcherbirds may also nest or perch in the branches.

Yellow-tailed black cockatoos are among the birds that may feed on swamp she-oak seeds.

What is the life cycle of swamp she-oaks?

Swamp she-oaks are dioecious, which means male and female flowers usually grow on separate trees. Male trees produce pollen on flower spikes near the ends of branchlets. Female trees produce small red flowers that can develop into woody cones after pollination.

The cones mature and release small winged seeds that can be carried by wind or water. Some seeds land in suitable damp soil and grow into seedlings. Swamp she-oaks can also spread by suckering, where new shoots grow from existing roots. This helps them form groves and regrow after disturbance.

Male swamp she-oaks produce flower spikes on the end of their branchlets.

Swamp she-oak seeds have small wings that help them disperse.

What adaptations do swamp she-oaks have to help them survive?

Swamp she-oaks are adapted to wet, sometimes salty and low-oxygen soils. Their spreading roots help them take up water and nutrients in creekside and estuary habitats. They can also tolerate some salt and waterlogging, which helps them survive where many other trees cannot grow.

Their green branchlets do much of the photosynthesis, while their true leaves are reduced to tiny scales. This helps reduce water loss. The woody cones protect seeds until they are ready to be released, and suckering from roots helps swamp she-oaks regrow and form dense stands after disturbance.

Tiny scale leaves help reduce water loss, while green branchlets carry out photosynthesis.

Woody swamp she-oak cones protect the seeds inside.

Why are swamp she-oaks important?

Swamp she-oaks are important creekside and estuary trees. Their roots help hold soil together, reduce erosion and protect banks from moving water. Their fallen branchlets add leaf litter to the ground, where fungi, bacteria and small invertebrates help recycle nutrients.

Swamp she-oak groves provide shade, shelter, nesting places and food for wildlife. They are also part of threatened floodplain and coastal wetland ecosystems in NSW. Protecting healthy swamp she-oak stands helps protect animals, water quality, soil stability and the natural links between creeks, wetlands, saltmarsh and mangrove forests.

Swamp she-oak groves help protect creekside habitats in Field of Mars Reserve.

How can you help swamp she-oaks?

You can help swamp she-oaks by protecting creek banks, wetlands and bushland edges. Stay on tracks, avoid trampling roots and seedlings, and do not pull off cones, bark or branchlets. Keeping rubbish, chemicals, soil and garden waste out of drains and creeks also helps protect the water environments where swamp she-oaks grow.

Students can help by learning to identify swamp she-oaks, observing animals that use them, joining local bushcare activities and sharing why creekside plants are important. Planting local native species can help wildlife, but swamp she-oaks should only be planted where they are suitable for the site and will not damage drains, pipes or small garden spaces.

Healthy swamp she-oaks are best protected by caring for creekside bushland.

Related fact sheets

More plant fact sheets

• Plant fact sheets – Explore native plant fact sheets about trees, shrubs, grasses and other plants of Sydney and NSW.
• Grey mangrove fact sheet – Compare another wetland tree that grows near salty water and protects shorelines.
• Paper-bark tree fact sheet – Learn about another moisture-loving tree found around wetlands and waterways.

Habitats and ecosystems

• Field of Mars Reserve fact sheet – Learn about the local reserve where swamp she-oaks grow near Buffalo Creek.
• Mangrove forest fact sheet – Explore another coastal and estuarine ecosystem connected to sheltered waterways.
• Coastal salt marsh fact sheet – Discover a nearby wetland habitat that can occur beside swamp she-oak and mangrove communities.
• Water habitats fact sheet – Find out how creeks, ponds and wetlands support plant and animal life cycles.

Animals that use this habitat

• Yellow-tailed black cockatoo fact sheet – Learn about a large cockatoo that may feed on she-oak seeds and other native plant material.
• Crimson rosella fact sheet – Explore a strong-beaked parrot that feeds on seeds, fruit and flowers.
• Long-nosed bandicoot fact sheet – Learn about a native mammal that forages in soil and leaf litter around bushland plants.

Food webs and ecological relationships

• Tree habitats fact sheet – Discover how trees provide food, shelter, nesting places and perches for wildlife.
• Birds fact sheet – Learn how birds use plants for food, nesting, shelter and movement through habitats.
• Invertebrate fact sheets – Explore insects, spiders and other small animals that live in leaf litter, bark, flowers and branches.

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