How to Grow Johnsonii Grass Tree
iNaturalist
Johnsonii Grass Tree
Xanthorrhoea johnsonii
shrubXanthorrhoea johnsonii is a distinctive Australian native shrub characterized by a stout trunk topped with a dense rosette of long, narrow, grass-like leaves. This striking architectural plant produces tall flower spikes with small, cream-colored flowers that attract wildlife. It is a slow-growing, long-lived plant highly valued for its dramatic form and low-maintenance requirements.
When should you plant Johnsonii Grass Tree in your zone?
Get a personalized planting timeline — when to start seeds, transplant, and harvest — based on your USDA zone and local frost dates. Free to start.
Example Johnsonii Grass Tree timeline · Pittsburgh, PA (Zone 6b)
-
Plant Johnsonii Grass Tree
Around Apr 17Near Pittsburgh's average last spring frost.
-
Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
-
Harvest Johnsonii Grass Tree
Late summer into fallBefore the first fall frost (≈ Nov 8)
Sample dates for Pittsburgh, PA. Sign up to get exact Johnsonii Grass Tree dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in USDA zones 9b-11, tolerates mild frosts and warm temperate climates
Sign up free to see if Johnsonii Grass Tree grows in your zone — and get a personalized planting timeline.
Get my Johnsonii Grass Tree timeline →Growth Stages
Establishment
1-2 yearsYoung plant with small rosette of grass-like leaves, developing trunk base
Establish regular deep watering schedule; protect from frost; ensure excellent drainage; do not fertilize heavily; mulch lightly around (not touching) the base
Vegetative Growth
2-5 yearsTrunk extends upward, rosette becomes fuller and more dense; leaf length increases
Maintain consistent watering during dry spells; minimal fertilizer needed; remove dead leaves only when fully brown; watch for drainage issues
Maturation
Ongoing (maturity reached at 5-10 years)Distinctive thick trunk formed; dense crown of long leaves; plant reaches characteristic architectural form
Reduce supplemental watering; allow natural rainfall to sustain; minimal fertilization; prune only dead material; plant becomes very drought tolerant
Flowering
Several weeks of bloom; spike persists monthsTall, columnar flower spike (inflorescence) emerges from center of leaf rosette; spike reaches 3-6 feet tall with many small cream-colored flowers
Occurs sporadically, sometimes annually once mature; flowers attract birds and insects; do not cut off spike until fully dry; allow natural seed dispersal
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
-
Prevent with excellent drainage and reduced watering; remove affected plants; improve soil aeration
-
Spray with insecticidal soap or horticultural oil; remove heavily infested leaves
-
Increase humidity if possible; spray with water; use miticide if severe
-
Prune affected leaves; treat with horticultural oil or insecticide; monitor regularly
Uses
Ornamental focal point
LandscapeXanthorrhoea johnsonii is an exceptional architectural specimen plant that creates dramatic visual interest in landscapes. Its distinctive silhouette and dramatic form make it ideal as a focal point in contemporary, xeriscape, or tropical-inspired gardens. [source]
Bird and pollinator attraction
WildlifeThe tall flower spikes attract native birds, bees, and other pollinators, supporting local ecosystems. This plant is particularly valuable in native gardens and wildlife corridors. [source]
Dried flower arrangements
CraftThe dried flower spikes can be harvested and used in dried floral arrangements and botanical crafts. The sturdy structure and natural form make them valuable decorative elements. [source]
Low-maintenance landscaping
HouseholdOnce established, Xanthorrhoea johnsonii requires minimal maintenance, no fertilization, and drought tolerance makes it ideal for water-conscious landscaping and sustainable gardens. [source]
Harvest Tips
Not typically harvested. Allow flowers to mature and dry on plant for seed dispersal. Dried flower spikes can be cut and used for dried arrangements once fully brown.
Fun Facts
- 🌱 Xanthorrhoea species are sometimes called 'grass trees' or 'blackboys' (though the latter term is now considered outdated), and can live for 150+ years, making them truly long-lived landscape specimens.
- 🌱 The resinous trunk and flower spikes of Xanthorrhoea were traditionally used by Australian Aboriginal people for various purposes, including fire-making and tool production.
- 🌱 The flower spike can grow exceptionally tall—sometimes 4-6 feet or more—and flowers are rich in nectar, making them a significant food source for native Australian birds and insects.
Gardening Terms
New to gardening? Learn about terms used in this guide:
Join 30,000 gardeners planning their gardens with LizPlants.
Get your personalized Johnsonii Grass Tree planting timeline
Tell us your zip code and we'll calculate exactly when to start Johnsonii Grass Tree seeds, transplant seedlings, and harvest — based on your USDA zone and local frost dates. Includes calendar reminders and printable task lists. Free to start.
Get my Johnsonii Grass Tree timeline →