Xanthorrhoea The Australian Grass Tree

Xanthorrhoea is a icon of the Australian bush and the Australian coastal garden. Whether you are designing a small garden, a medium sized garden or a large garden, the Australian Grass tree or Xanthorrhoea is a great choice. For a small garden, it is a great focal point with its dark charcoal coloured truck its green leaves and its beige cream coloured flowers. The impact can be even greater when lite with some well designed garden lighting.

How much do grass trees grow per year?

For small gardens, slow growing plants like these are ideal. With a growth rate of around 25mm per year, it will take a long time to outgrow any garden. In larger gardens, the irregularly shaped trunk and profuse leaves can be used to soften any sharp edges in your design. It is estimated that Xanthorrhoea will live to around 400 years. It is also a great pot plant, but should be repotted at least every 50 years or so. To create an interesting contrast, consider planting some orange, red, or pink Anigozanthos ‘Bush Pearl’ kangaroo paws nearby. Kangaroo paws also thrive in similar growing conditions.

How many species of Xanthorrhoea are there?

It will surprise many people to learn that there are around 30 species and that these are only found in Australia. As with most plants, it is important to understand their natural habitat to recreate ideal growing conditions.

How do you take care of a grass tree?

In our blog on orchids and vertical gardens we mentioned the symbiotic relationship with mycorrhizal fungi helps plants to survive nutrient poor conditions. This means that if you take care of the mycorrhizal fungi, you take care of the host plant. To boost mycorrhizal fungi try diluting 1/2 cup of brown sugar in 5 litres of water. Apply this solution every month.

How did Xanthorrhoea get its name?

Every year of its growth, the Xanthorrhoea species produces a ring of leaves around the trunk. At the base of the leaves are resin secreting glands. It is this resin that gives the plant its name. The names Xanthorrhoea comes from the ancient Greek – Xanthos meaning yellow and rhoia meaning flowing. This resin binds the leaf bases together into a bundle. The glued bundle of leaves forms an effective insulator that restricts air circulation and combustion in the trunk. The resin was used as a glue by the original inhabitants of Australia for making tools and spears. Even if the trunk is destroyed by fire, plants can regenerate from root or stem buds.


Garden design with Xanthorrhoea - Reds Landscaping & Design


Types of Xanthorrhoea

Some species of Xanthorrhoea have been known to reach 6 metres, whilst some others, like Xanthorrhoea gracilis, have a branched trunk. Some species, like the swamp grass tree Xanthorrhoea fulva, have no trunks at all.
In Queensland and northern NSW, a common and widespread species is Xanthorrhoea johnsonii. The nectar rich flower spikes attract birds, bees, and butterflies.

Xanthorrhoea johnsonii. Mareeba, Queensland - Reds Landscaping & Design
Xanthorrhoea johnsonii. Mareeba, Queensland


Xanthorrhoea glauca is another one native to Queensland and New South Wales. The blue grey green leaves give the plant its glauca name. γλαυκός or glaukós, comes from the ancient Greek for "blue-green." When designing your landscape, use contrasting mulch to highlight the rich colour.

The blue-green leaves of Xanthorrhoea glauca - Reds Landscaping & Design
The blue-green leaves of Xanthorrhoea glauca create a great contrast with pebbles or stone mulch.

Swamp grass tree Xanthorrhoea fulva. This species has been know to hybridise with both glauca and johnsonii.


Xanthorrhoea fulva or Swamp Grass Tree - Reds Landscaping & Design
Xanthorrhoea fulva or Swamp Grass Tree.

This compact species with no trunk is great for any sized garden and is more tolerant of heavier soils. Like the other species, it it a great way to attract wildlife to your garden.


Grass trees are great for attracting wildlife including birds to your garden - Reds Landscaping & Design
Grass trees are great for attracting wildlife including birds to your garden.


Grass trees are great for bees and other insects - Reds Landscaping & Design
Grass trees are great for bees and other insects.

Do grass trees need to be burnt?

Xanthorrhoeas have adapted over the years to not only endure bushfires but to thrive on them. Grass trees have evolved to induce flowering after bushfires as this is the optimal time for offspring to germinate. With little to no competition around and with ash present in the soil, the grass tree germination strike rate is greatly improved. It has been said that some people even do controlled burns on their grass trees using chicken wire and newspaper. It is believed by many that this artificial simulation of a bushfire can induce the plant to flower or stimulate new foliage and root growth after transplanting.

Choosing and caring for your Xanthorrhoea

It is very important to only buy your Xanthorrhoea from a reputable garden nursery. Grass trees are often harvested as a food source. This means that they are usually removed from the land and re-potted for sale. They have a Xanthorrhoea Glauca hybrid which is entirely pot grown. It is important to note that it is illegal to remove plants from the bush in Queensland without a permit.
A reputable supplier should always be used in this process to ensure the mycorrhizal fungi are maintained in good contact with the grass tree root system in the potting process. When planting your Xanthorrhoea, ensure you keep as much soil as possible around the roots. These plants prefer sandy, well drained soil and full sun. If you have heavy clay soil, dig out an area equivalent to around 2-3 times the pot diameter and replace the soil with a sandy loam soil. Building up the level of the garden or adding extra sub soil drainage will help.

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