Grass tree fact sheet – gulgadya

What is a grass tree?

Grass trees, scientifically known as Xanthorrhoea, are a plant that belong to the Asphodelaceae family. They can be found in the understorey layers of  eucalypt forests  and in heathlands. There are 66 species of grass tree and they are only found in Australia.

Grass trees range in height from one metre to 6 metres tall, with  Xanthorrhoea media  growing to around 3 metres. The leaves of the grass tree are hard, long and narrow.

Grass trees such as  Xanothorrhoea media  develop a ‘trunk’ from old leaf bases stacked on top of each other.

When flowering grass trees develop a 2 to 4 metre long spear-like spike that grows out of the middle of the plant. The top of the spike is covered in hundreds of small flowers.

Growth and flowering is often stimulated by bushfire.

Xanthorrhoea media in the Field of Mars Reserve

Where are grass trees found?

Grass trees are native to Australia and found in all states and territories, particularly on the east and west coast. Grass trees grow well in nutrient poor soils and respond to bushfires by flowering profusely. The species found within Field of Mars Reserve is Xanthorrhoea media.

The 'stem' of a grass tree is made up of old leaf bases.

What role do grass trees play in the ecosystem?

Grass trees provide food for birds, insects and mammals that feast on their nectar, pollen and seeds. Beetle larvae and carpenter bees also live within the flower spikes.

Reptiles and small native mammals such as  bandicoots  can shelter and nest in the ‘skirt’ of leaves around the trunk. This 'skirt' is formed as the leaves fall around the trunk of the grass tree as they age.

The ability of grass trees to re-sprout and quickly produce flowers after a bushfire makes them a lifeline for animals living in recently burnt areas

Grass trees are pollinated by invertebrates such as bees.

How are grass trees used by Aboriginal Peoples?

The Darug Peoples of the Sydney basin refer to the grass tree as gulgadya. Grass trees are very important to Aboriginal Peoples as they are a highly valued resource with many uses.

The resin, called yakka, found in the base of the tree is mixed with kangaroo droppings and used as a glue to attach tool heads to handles and can also be used to seal containers –  coolamons –  for use with water.

The dry long flower spike is used to make land and fishing spears. Fishing spears have 3 or 4 prongs glued to the shaft, each with barbs glued to the end. The prongs and barbs are glued using grass tree resin.

The flowers of the grass tree are soaked in water to make a sweet drink and the leaves and roots of some species can be eaten. Seeds are also collected and ground into flour to make damper.

The base of some grass trees leaves can be eaten.

What structural adaptations do grass trees have to their environment?

Most grass trees are adapted to fire. They have a thick coating of dead leaves called a 'skirt' around their base. The skirt acts as insulation to protect the stem from flames and heat. The living growth-point of the grass tree is buried underground and this is covered above by many moist, tightly packed leaf bases.

Many species of grass tree are stimulated to flower after exposure to fire. The leaves of the grass trees produce toxic chemicals to deter herbivores from eating them.

Grass trees have a symbiotic relationship with mycorrhiza, a type of fungi, deep within its root system. A symbiotic relationship is one that benefits both species. The fungi increases the grass tree root’s access to water and nutrients in the soil helping to increase tree growth especially in poor conditions. The grass tree in return supplies the fungi with sugars.

Grass trees are often the first green shoots to appear after a bushfire.

How do grass trees grow and reproduce?

Grass trees are perennial, which means they live for many years. Some species can potentially live for 600 years. They are very slow growing plants with their 'trunks' only growing up to 6 centimetres per year for the taller species. The ‘trunk’ is formed from old leaf bases stacked up on each other and stuck together with their resin.

Tall grass trees in Lane Cove National Park. Their black trunks are evidence of surviving many bushfires.

To reproduce grass trees will send up a towering green spike that erupts into thousands of tiny cream flowers. Grass trees are pollinated by a number of different pollinators such as insects, birds and mammals.

Once pollinated the flowers form a tough, pointed seed pod that starts green and dries to black. Some grass tree flower spikes can produce up to 10,000 seeds.

Grass trees with their tall green flower spikes. There is an old dry flower spike on the right.

Grass tree flower spike in covered in hundreds of tiny nectar-rich flowers. The old spike on the right contains dried seed pods.

Related Fact Sheets

More plant fact sheets

• Hairpin banksia fact sheet
• Scribbly gum fact sheet
• Sydney red gum fact sheet

Habitats and environments where grass trees grow

• Field of Mars Reserve fact sheet
• Eucalypt forest fact sheet

Animals that use grass trees

• Long-nosed bandicoot fact sheet
• Rainbow lorikeet fact sheet
• Insects fact sheet