Xanthorrhoea johnsonii
forest grasstree
Eastern Australia (Queensland, New South Wales)
Overview
Xanthorrhoea johnsonii is an evergreen perennial in the Asphodelaceae forming a single thick trunk topped with a dense crown of long, narrow leaves. The trunk develops slowly, at roughly 0.4-0.8 inch (1-2 cm) per year, and reaches 3-10 feet (0.9-3 m) tall over many decades, often blackened by past fire. Leaves are stiff, grass-like, and roughly square in cross-section, 1.5-3 feet (45-90 cm) long and about 0.1 inch (2-3 mm) wide, arching from the crown in shades of green to grey-green. In maturity or after fire, the plant sends up a flowering spike on a bare stalk, with cream flowers packed along a cylindrical head 3-7 feet (0.9-2 m) tall that opens over several weeks. Old leaves persist as a brown skirt below the green crown unless removed by fire. A resin secreted at the leaf bases binds the trunk. Growth is very slow, and trunk-forming plants may be several decades old. Plants are slow to recover from root disturbance and transplant poorly once established.
Native Range
Native to eastern Australia, mainly Queensland and north-eastern New South Wales. Grows in dry sclerophyll forest, woodland, and heath on well-drained, low-nutrient sandy and gravelly soils, often on ridges and slopes.Suggested Uses
Planted as a specimen in native, low-water, and dry-climate gardens on free-draining soil, spaced 3-6 feet (0.9-1.8 m) apart. Used in fire-adapted and habitat landscapes. Slow growth and sensitivity to root disturbance limit its use as a transplanted advanced specimen.How to Identify
Appearance
Size & Dimensions
Height3' - 10'
Width/Spread3' - 5'
Reaches mature size in approximately 30 years
Colors
Bloom Information
Flowering is irregular and often triggered by fire, occurring mainly in spring and early summer. When it occurs, the spike opens its cream flowers over 4-8 weeks, progressing up the stalk. Many years can pass between flowering events on an individual plant.
Detailed Descriptions
Foliage Description
Green to grey-greenGrowing Conditions
Sun Requirements
Requires 6-10 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Grows in full sun to light shade in sharply drained sandy or gravelly soil of low fertility. Water sparingly; established plants tolerate long dry periods and are sensitive to wet, poorly drained soil, which causes root rot from Phytophthora. Phosphorus-rich fertilisers and rich soils damage the roots. The species grows very slowly and may take decades to form a visible trunk. Root disturbance during transplanting often kills established plants. Routine pest treatment is rarely needed.Pruning
Old brown leaves can be left as a skirt or trimmed from the trunk to expose it. Spent flower spikes can be cut once seed has shed. The green leaf crown holds the single growing point, so cutting it removes the plant's only point of growth.Pruning Schedule
J
F
M
A
M
J
J
A
S
O
N
D
summer
Container Growing
✓ Suitable for container growing
Minimum container size: 10 gallons