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Your complete guide to grass trees

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Your complete guide to grass trees
By
All Green
All Green
July 20, 2021
5
minute read

Understanding this unique Australian plant

Grass trees are a quintessential example of an Australian native plant. It grows naturally right across Australia's diverse landscapes. Grass tree thrives in stony, sandy, and low-nutrient soils and responds to fire with vibrant plumage.

Grass trees come in a wide variety of species with different sizes, colours. The species that are local to your area will be most likely to thrive in your garden.  

[content_aside]Native grass tree makes a stunning feature plant in any landscape. Talk to the horticulturalists at All Green Nursery and Garden about growing grass trees in Melbourne.[/content_aside]

Connection to Australia's history

grass trees landscape

Grass trees have a spiritual significance for Aboriginal people. When growing atop a hill, the trees cast a silhouette across the surrounding landscape. The Aboriginal name for grass tree is 'balga' or black boy, referring to the blackened trunk of the plant that remains after a fire sweeps a region. You may also hear grass tree referred to as 'yacca', a name that may originate from the Kaurna people in South Australia.  

Traditional Aboriginal techniques use grass tree stalks to start a fire, utilising the friction between the thick and thin parts of the stalks. The resin from the trunk makes a strong glue or waterproof varnish both by native Australians and European settlers.

In Victoria, the Grey Grass Tree (X. glauca anguvstifolia) is a threatened species under the Flora and Fauna Guarantee Act.

Grass tree trunk formation

Grass tree gets its name from the grass-like foliage that plumes from the base. The trunk of the grass tree doesn't form rings like a regular tree trunk. Instead, the grass tree trunk consists of the tightly-packed leaf base of old grass foliage, held together by the resin produced by the plant.

Not all species of Xanthorrhoea will form a trunk above ground. Species with resilience to fire will survive because the living growth point is underground, protected by the tightly-packed leaf base.

Grass tree flowers and pruning

grass trees flowers

This unique Australian plant may flower after a fire. Flowers are long spikes, often white or yellow, that will grow to a height between one and three metres. Flower stalks may grow up to 2.5cm in a day!

These flowers bloom rapidly after a fire, providing a source of food for insects and birds in an otherwise scorched environment. Birds, bats and insects pollinate the flowers, which can produce up to 10,000 seeds.

While fire plays a pivotal role in the life of a grass tree in the bush, it's not safe or practical to burn grass trees in your garden. Instead, shape the tree by pruning the foliage from underneath. Pruning keeps the new growth at the centre while reducing decaying leaves to ensure the tree remains fresh and healthy.

Grass tree maintenance

Grass trees with an established root system have the highest replanting success rate. After replanting, the tree needs around 30-60L of water, depending on its size, for the first two seasons. After this, the plant becomes self-sufficient.

Grass tree is low-maintenance if correctly replanted with the original soil. You can feed it with a native compatible fertiliser every 6 to 12 months.

The only disease this resilient plant contracts is scale, a white insect that appears on the tree's inner crown. White oil helps to treat scale quickly. Spray weekly onto the affected areas, rubbing the leaves to dislodge the insects.

In the bush, the grass tree is also susceptible to phytophthora cinnamonia, a mould that attacks the delicate tree root system. Generally speaking, it is less likely to occur in a tree propagated for transplanting.

How much does a grass tree grow each year?

Grass tree grows around 1cm each year. These trees can live for centuries, reaching heights of over three metres.

If you're planting a grass tree in your garden, a smaller plant of up to a metre will grow slowly.

What to plant with a grass tree

When planning your garden, we recommend choosing plants that grow in a similar environment. Grass tree grows will with kangaroo paw (Anigozanthos), a native flowering plant that thrives in sunlight and sandy, well-drained soil.

Grass tree grows well in any native rockery or amongst plants such as banksias or eucalyptus. Grass trees prefer full sun, so planting native grasses and other drought-tolerant plants allow the plants to thrive.

For the ground cover to plant alongside grass trees, look for plants that thrive in full sunlight and rocky soil, such as pig face or yellow buttons. These vibrant plants will add a pop of colour against the dark truck and grey-green foliage of your grass tree.

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