Xanthorrhoea glauca (Queensland Grasstree)

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Xanthorrhoea, Genus, glauca, Species,

Genus & species

Queensland grasstree

Asphodelaceae Eastern Australia

Attracts Pollinators Attracts Butterflies Drought Tolerant Container Friendly

SunFull Sun – Part Shade

WaterVery Low · drought-tolerant

HardinessZones 9–10

Overview

Xanthorrhoea glauca is a slow-growing grasstree forming a stout, blackened woody trunk topped by a dense crown of long, narrow, blue-green leaves. The trunk reaches 6-16 feet (2-5 m) over many decades and may branch in old plants, while the arching leaves are 24-48 inches (60-120 cm) long and roughly square in cross-section, the blue-grey colour giving the species its name. From the centre of the crown a tall flowering spike rises after suitable conditions or fire, made of a bare lower scape and a dense cylindrical spike of small cream flowers, the whole structure reaching 6-13 feet (2-4 m). The flowers are rich in nectar and open over several weeks. The trunk is built from accumulated leaf bases bound by resin, and the plant grows only a few centimetres in height each year, so large specimens are very old. It grows on rocky slopes and ridges in eastern Australia. Its slow growth and sensitivity to root disturbance make it difficult and slow to establish in cultivation.

Native Range

Xanthorrhoea glauca is native to eastern Australia, in Queensland and New South Wales. It grows on rocky hillsides, ridges, and gorges in dry sclerophyll forest and woodland, often on shallow stony soils.

Suggested Uses

Used as a long-lived feature plant in rockeries, dry native gardens, and large containers with sharp drainage. The architectural trunk and grassy crown suit water-wise and bushland-style plantings. It is grown for habitat value, as the flowers feed nectar-seeking birds and insects.

How to Identify

Recognized by a thick black woody trunk topped with a dense skirt of long, narrow blue-grey leaves 24-48 inches (60-120 cm) long that are square in cross-section. A tall flowering spike of small cream flowers on a bare scape rises from the crown, reaching 6-13 feet (2-4 m). The blue-grey square leaves separate it from green-leaved grasstree species.

Appearance

Size & Dimensions

Height6' - 16'

Width/Spread4' - 8'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~6 weeks

Flowers: September–December

Spring Summer

Flowering is irregular and often triggered by fire or by warm conditions after rain, mainly in spring and summer. The cream flowers open in waves up the dense spike over several weeks. Heavy nectar flow draws bees, birds, and other insects.

Detailed Descriptions

Foliage Description

blue-grey green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 5-12 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

Soil Requirements

pH Range5.0 - 7.0 (Acidic to neutral)

3579

Soil Types

rocky sand loam

Drainagewell drained

Water & Climate

Water Needs

Very Low

Frost Tolerance

hardy

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Grows in full sun to light shade on very free-draining rocky or sandy soils and tolerates extended drought once established. It is highly sensitive to root disturbance and to wet, poorly drained soil, which cause root rot and sudden collapse. The plant grows extremely slowly, adding only a little height each year, so it serves as a long-term feature. It is grown from seed, with transplanting of established plants risky and often fatal. It tolerates fire, which can prompt flowering and clears competing growth. Watering is kept minimal, especially in humid conditions.

Pruning

Old, dead outer leaves are trimmed away where a clean trunk is wanted, though many growers leave the natural leaf skirt intact. Spent flower spikes are cut once seed is shed. No other pruning is needed for this slow-growing plant.