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Growing Grass Trees - The Queensland Experience

Harry Franz

Grass trees (Xanthorrhoea species) are uniquely Australian. All varieties of Queensland Grass trees are classified as Protected. It is now illegal to dig up wild plants anywhere without a licence. There are some licensed operators digging up wild plants for sale to the public. Some of these grass trees are salvaged from sites threatened by development, mining or other processes. Many grass trees dug up from the wild die even when the best practises are used. They resent disturbance and can take up to two years to die even if they look good for awhile.

Grass trees are easily grown from seed. The seed remains viable for up to two years at room temperature. Dried seed will live for many years if kept in a refrigerator. Store in moisture proof containers. Freezing would probably kill the seed.

Xanthorrhoea minor    Xanthorrhoea sp fruits

A seed-grown Xanthorrhoea minor in a native garden, showing the overall plant and the clusters of small flowers

To propagate seed, use a very sandy mix. Seedlings are very intolerant of poor water quality and can die quickly. Use tank water for good results if available. Seedling grass trees usually grow quickly when planted into the garden from about two years of age.

They do not like waterlogged soils. They will grow in full sun or dappled shade, and respond to a light fertilising of blood and bone or manures, can use mulch as normal. A regular watering is necessary only during establishment, in fact over watering can be detrimental to some species.

Local species appear to be frost hardy. Avoid using herbicides in close proximity to grass trees. Avoid spraying with any oil based insecticides as losses of plants have occurred, particularly when sprayed onto the growing centres of the plants.

Some species appear to flower better after bush fires, Xanthorrhoea latifolia is one of these. Xanthorrhoea glauca is damaged by fire and may not flower for some years after the skirt of old leaves burns. Xanthorrhoea glauca flowers irregularly at best.

The ABC Gardening Show suggested that transplanted grass trees would benefit from several applications of a brown sugar and water mixture to stimulate micro-organisms. The mixing rate is half a cup of brown sugar to 5 litres of water. Small plants would require a smaller quantity of mixture. Water monthly with the brown sugar solution for two years.

From the newsletter of ANPSA's Wildlife and Native Plants Study Group, Spring/Summer 2008.

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