How to Grow Australian Grass Tree
Xanthorrhoea preissii
The Australian Grass Tree is one of the slowest-growing plants on earth — a 1 m trunk can be over 50 years old. Plant in full sun in sandy, perfectly drained soil. It resents disturbance — choose the final position carefully and do not move it once established. Water sparingly after planting and almost not at all once settled. Never fertilise with phosphorus — it is toxic to this plant. The dramatic flower spike, up to 2 m tall, may appear after fire, drought, or seasonal stress. Patience is the key virtue — this is a plant for decades, not seasons.
Yearly Lifecycle
Care Essentials
Almost never. This plant evolved in nutrient-poor soils — do not fertilise with phosphorus, which is toxic to it. If needed, apply a slow-release fertiliser labelled as phosphorus-free in late spring, once every 2-3 years at most.
Watch For
- Root rot in poorly drained or heavy soils
- Scale insects on the trunk
- Leaf blight in humid conditions
Companions
Kangaroo Paw (Anigozanthos), Grevillea, Banksia, Lomandra
Care Requirements
Light
Full sun, open position
Requires full sun and an open, exposed position. Does not tolerate shade. Evolved in harsh Australian sun and needs maximum light.
Watering
Almost none once established
Water deeply once a month during the first 2-3 years in summer drought. Once established, needs no supplemental watering. Never water in winter. Overwatering is fatal.
Fertilizing
Almost never, no phosphorus
Evolved in nutrient-poor soils. Never fertilise with phosphorus, which is toxic. At most, a phosphorus-free slow-release feed once every 2-3 years.
Growing Tips
Never fertilise with phosphorus
Phosphorus is toxic to Xanthorrhoea and most other Australian native plants. Use only phosphorus-free fertilisers, or better yet, none at all. Poor soil is exactly what this plant prefers.
Drainage is non-negotiable
The single most common cause of death is waterlogged soil. Plant on a slope, in a raised bed, or in pure sand if your soil is heavy. Never allow water to pool around the crown.
A flower spike is a good sign
The dramatic 2 m flower spike appears after the plant experiences stress — drought, fire, or a cold snap. It is not a sign that the plant is dying; it is the plant at its most spectacular. Enjoy it.
