How to grow grass tree
Overview
Xanthorrhoea australis, the grass tree, is a slow-growing Australian native with a tufted crown of fine, arching leaves atop a thick, woody trunk. It is grown for its striking silhouette, textural contrast, and resilience in dry, sunny gardens. The key to success is patience—it can take years to develop a visible trunk and must never have its roots disturbed after planting.
Varieties
- Xanthorrhoea australis 'Standard' — The typical form with a single trunk, reaching 2–3 m in 20 years.
- Xanthorrhoea australis 'Dwarf' — A compact, multi-stemmed selection from the Grampians, rarely exceeding 1 m.
Soil Preparation
Grass tree thrives in neutral to slightly acidic soil (pH 6.0–7.0) that is sandy or gravelly and free-draining. If your soil is heavy clay, raise the bed 30 cm with a mix of coarse sand and decomposed granite. Do not add compost or manure, which can retain too much moisture.
Growing Guide
Plant grass tree in full sun in well-drained, sandy or gravelly soil; avoid clay or wet areas. Dig a hole twice as wide as the root ball but no deeper, and backfill with native potting mix or coarse sand. Space specimens at least 1.5 m apart to allow for eventual spread. Water deeply once a week for the first summer, then reduce to monthly in cool seasons. Do not fertilise until the second year, and use only low-phosphorus native food.
Sowing
Seeds are slow to germinate (6–12 months) and best sown in a seed-raising mix with extra sand. Sow 5 mm deep, keep moist but not wet, and place in a warm, bright spot. Direct sowing is unreliable; use a pot or punnett and transplant carefully after 2 years.
Care
Feed with a low-phosphorus native fertiliser (e.g., 2:3:2) in early spring only. No regular pruning is needed; remove only dead or damaged leaves by hand. Avoid disturbing the root system once established, as grass tree has a single, sensitive taproot.
Companion Planting
Pair with other low-water natives such as kangaroo paw (Anigozanthos), grevillea, and banksia for a textured, bird-friendly garden. Avoid planting near thirsty lawns or irrigation-dependent shrubs, as grass tree resents wet feet. Also keep clear of invasive grasses that may compete for light and nutrients.
Common Pests & Risks
Grass tree is generally pest-free, but root rot (Phytophthora) can strike in poorly drained or overwatered soil. Scale insects may appear on the trunk; treat with a soft brush or horticultural oil. Snails and slugs sometimes graze on new leaves in damp weather—use iron-based bait sparingly.
Troubleshooting
Yellowing leaves: caused by overwatering or poor drainage—reduce watering and check soil. Brown leaf tips: caused by dry air or underwatering in hot weather—increase misting or water deeply. Slow growth: normal for the first 5 years; do not fertilise more. Trunk rot: caused by water pooling at the base—ensure soil is free-draining. Leaf drop: caused by transplant shock—avoid moving once planted.