Grass tree

Sun

Full sun; tolerates light shade but develops a less dense crown.

Water

Water regularly while establishing, allowing the soil to drain between waterings. Established plants tolerate drought but may need occasional deep watering during prolonged dry weather.

Soil

Well-drained sandy or gravelly soil, preferably acidic to neutral. Avoid heavy, waterlogged ground; use a raised mound where drainage is marginal.

Height

10-16 ft (3-5 m) over many decades; flowering spikes can extend above the crown.

Spread

5-8 ft (1.5-2.4 m)

Flowers

Usually spring to summer, though flowering is irregular: tiny cream-white flowers densely cover a tall, upright spike. Fire can stimulate flowering, but is not necessary.

Foliage

Evergreen. Long, narrow, stiff green to blue-green leaves form a rounded, arching crown; old leaves can remain as a skirt around the trunk.

Growth

Very slow; developing a substantial trunk takes decades.

Care needed

Medium

• Pollinators
• Drought tolerant
• Heat tolerant
• Wildlife
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Hard

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   7 ft (2 m)

2. After 1 year

   7 ft (2.1 m)

3. After 2 years

   7 ft (2.1 m)

4. After 3 years

   7 ft (2.2 m)

5. After 5 years

   8 ft (2.3 m)

About 32 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Native to

Australia

Growth rate

Slow

• Choose a nursery-propagated plant or a legally salvaged specimen with an established root system; avoid freshly dug, poorly rooted trunks.
• Plant with the crown at its original depth and keep the root ball intact; do not tease out the roots.
• Water the root zone during establishment, but never leave it standing in water.
• Feed sparingly in spring with a low-phosphorus fertiliser formulated for Australian native plants.
• Keep mulch away from the trunk and crown; gravel mulch suits well-drained sites.
• In cold climates, use a container while the plant is manageable and overwinter it in a bright, frost-free place.

Pruning. Remove spent flower stalks near their base once they have dried, unless you want seed. Leave healthy leaves and the growing tip untouched; remove dead leaves only as needed, and do not burn garden plants to encourage flowering.

Spring

Plant after frost risk has passed, keeping the root ball undisturbed.

Spring

Apply a light dose of low-phosphorus native-plant fertiliser if growth is weak.

Summer

Check newly planted specimens regularly and water deeply when the root zone begins to dry.

Late summer

Leave flowering spikes for wildlife and seed, or cut them off once dry.

Autumn

Check drainage and move container plants under cover before frost in cold regions.

Winter

Keep sheltered container plants bright and only lightly watered; prevent prolonged saturation outdoors.

• Use a single mature specimen as a focal point in a gravel courtyard, with space around its arching crown.
• Combine with banksias, grevilleas and low native grasses in an Australian native planting.
• Repeat young plants among rocks and gravel for a strong rhythm in an architectural garden.
• Place against a plain wall where the leaf silhouette and tall flower spike can be seen clearly.

Garden styles it suits: Australian native, Architectural minimal, Contemporary minimal, Dry gravel garden, Desert / xeriscape and Wildlife garden.

Plant it with: Kangaroo paw, Lomandra, Wallaby grass, Dwarf banksia, Prostrate grevillea and Waxflower.

Wildlife: Flower spikes provide nectar and pollen for bees, other insects and nectar-feeding birds. The persistent leaf skirt can shelter small animals and invertebrates.

• Root rot, including Phytophthora: prevent with excellent drainage, clean nursery stock and careful watering; an established infection can be fatal.
• Transplant failure: buy a well-rooted plant, keep its roots intact and maintain even moisture during establishment without waterlogging.
• Frost damage: shelter young plants and protect the crown from severe frost; cold combined with wet soil is particularly damaging.
• Poor growth after feeding: avoid heavy fertilising and high-phosphorus products; use a low-phosphorus native-plant formulation sparingly.

Not known to be toxic to people, cats or dogs, although species-specific safety information is limited. Grass-tree foliage and flowering growth have been associated with livestock poisoning; keep horses and other grazing animals from eating it. The stiff leaf tips can scratch skin and eyes.

• Kingia (Kingia australis)

  It has a similar trunk and grassy crown, but produces several stalks topped by rounded flower heads rather than a long, densely flowered spike.

• Cabbage tree (Cordyline australis)

  Its leaves are much broader and strap-shaped, mature trunks commonly branch, and its small flowers appear in branching clusters.

• Spiny-headed mat-rush (Lomandra longifolia)

  It forms a ground-level clump of broader, flat leaves rather than a substantial trunk, and bears short, branching flower clusters among the foliage.

Xanthorrhoea comes from Greek words meaning 'yellow flow', referring to the resin produced by plants in the genus.

Propagation. Grow from fresh seed in a free-draining seed mix, kept warm and lightly moist. Seedlings develop slowly; pot them on carefully with minimal root disturbance. Mature trunks are not suitable for ordinary division or cuttings.

Accepted botanical name

Xanthorrhoea johnsonii

Native range

New South Wales and Queensland.

Sources: GBIF (CC BY 4.0) and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.