Grass Tree (Xanthorrhoea)
Picture this scene. You are driving through the outback. The ground is a never ending expanse of red soil, the sky is rich blue. Under the blazing sun you catch a glimpse of long haired people standing by the side of the road, holding spears. Look again. Those ‘people’ are the iconic Australian plant Xanthorrhoea commonly known as the Grass Tree. Their very appearance led to them being known as Black Boys in the past, though this name is now considered offensive and not often used.
There are 28 species of this perennial grass found throughout Australia ranging from 500mm high mounds up to 6 metre high specimens with hauntingly sculptural forms. All are extremely slow growing with the fastest putting on about 25mm per year. Some of the larger ones you see may be 600 years old.
The ‘spear’ is a flower spike which can rise up to 5 metres above the plant with a head covered in small white or cream coloured flowers. The trunk is, in fact, a ring of dead leaf bases surrounding a cluster of aerial roots which feed the actively growing crown. The trunk has adapted to protect the roots from grass fires and bush fires. As a result it gets the charcoal coating which gives it the black look.
Grass trees rely on a mychorrhizal relationship with fungi in the soil to supply them with nutrients. Therefore it is critical that any time one is relocated, a large amount of the original soil is relocated with the plant. When transplanting a potted specimen, do not knock away the soil around the base. Apply a dose of seaweed extract to stimulate new roots.
Seeds germinate readily between 5-7 weeks and this exercise can be very rewarding for the amateur propagator, though as the Grass Tree grows so slowly, don’t expect to see a tall or multi trunked plant in your lifetime.
In general, Grass Trees are hardy. The key points to remember are to plant them in full sun with well drained soil. Over watering can lead to root rot and eventual death of the plant. Many species survive in harsh conditions. While their nutrient requirements are low, several home growers I know have suggested that a cup of sugar around the base can stimulate growth and flower development.
I have not experienced any pest related issues with grass trees. Brown tips or spots on the older leaves are okay. To determine the health of the plant, pay more attention to the new growth in the crown. It should be a brighter green than the mature leaves.
Xanthorrhea’s have benefited humans in many ways beyond their beauty. The indigenous population used the flower spike of some species as a spear. The perfumed, young flower head can be soaked in water to provide a sweet drink. A resin obtained from the base of the leaves can be used as a glue to bind on spear heads or a putty to repair water carriers. In fact it is this resin which gives the grass tree its botanic name. Xanthorrhoea is derived from the Greek xanthos, meaning yellow, and rheo, meaning to flow; referring to the resin. During the Second World War the resin was used as a coating on food tins to prevent rusting.
Many mature or trunked Grass Trees available from nurseries have been harvested from the bush or as a result of land clearing. There are strict laws governing the harvest and trade in Grass Trees to protect them. Ensure that any you buy have a registered tag.
Treat them well and this low maintenance plant will be a pleasure to you, your children and your children’s children.