Xanthorrhoea preissii (balga)

Xanthorrhoea preissii is restricted to south-west Western Australia, where it is widespread.

Prolific flowering of Xanthorrhoea preissii stimulated by fire. Boulder Rock, Western Australia (Image: Stephen Hopper)

A tree-like monocot (plant with a single seed-leaf) up to 5 m in height, with contractile roots that shrink vertically in seasonal drought conditions, and a trunk up to a height of more than 3 m. The stem is simple or branched and bears one to several uneven crowns. The thick, green leaves are up to 2.8 mm wide and 2.4 mm thick (but are very variable) and are diamond-shaped in cross-section. The scape (leafless flower stalk) is 60-100 cm long and 20-30 mm in diameter. The flowering spike is 150-250 cm long (about 2-3 times longer than the scape), and 30-60 mm wide.

The white or cream flowers are in spirals; the petals are recurved with a proboscis (elongated projection). The  flowers are insect-pollinated. Flowering occurs all year round, but the main season is from June to December. Prolific flowering is stimulated by fire. Arborescent (tree-like) monocots grow very slowly, grasstrees only increasing their stem height by approximately 1-2 cm per year. Recent attempts to age specimens of Xanthorrhoea preissii have given maximum age estimates ranging from 350 to 600 years.

Xanthorrhoea preissii is not a threatened species but it does form part of an endangered ecological community, the Corymbia calophylla – Xanthorrhoea preissii woodlands and shrublands of the Swan Coastal Plain. This community occurs in only one small part of the species’ range, on drier soils on the eastern part of the Swan Coastal Plain. There are approximately 41 hectares of this community remaining in south-west Australia and of these, only 0.3 hectares are formally protected in state Nature Reserves. Those areas not under protection are threatened by clearing, invasive weeds and changes in hydrology due to clearing and draining. The community is also susceptible to an excessive frequency of fires and to the fungal root pathogen Phytophthora cinnamomi.

Xanthorrhoea preissii (Image: Steve Ruddy)

The Aboriginal Noongar people of south-west Western Australia use the resin from Xanthorrhoea species as a reusable thermoplastic. Globules of resin are collected from the bases of old leaves close to the trunk, ground to powder, mixed with charcoal powder and plant fibre or kangaroo dung, heated and added to the handle of the implement under construction. Small bits are then reheated and used as required, for example to fix or replace stone knife blades (taap) and axe heads onto their wooden shafts.

The plants also provide a source of materials for hut (mia) construction and individual plant parts have a variety of other uses. The flowering stems can be used as fish spears and can also be rubbed together to make fire. The dried flower heads and old withered flowers are used as kindling, the leaves are used for torches, and young shoots are used for medicinal purposes to promote healing from wounds.

Flowering begins on the warm (north) side of plants so X. preissii can also act as a compass plant. Dead plants are also useful, and are owned by individuals as a source of highly nutritious bardi grubs (larvae of the beetle Bardistus cibarius). Xanthorrhoea preissii is also used in the restoration of vegetation on the sites of abandoned bauxite mines, and are planted widely in gardens and streetscaping.

Kew's Millennium Seed Bank Partnership aims to save plant life world wide, focusing on plants under threat and those of most use in the future. Seeds are dried, packaged and stored at a sub-zero temperature in our seed bank vault.

Description of seeds: Average 1,000 seed weight = 15.59 g.
Number of seed collections stored in the Millennium Seed Bank: One.
Seed storage behaviour: Orthodox?
Germination testing: 87% germination was achieved on moist filter paper medium, at a temperature of 23 °C, on a cycle of 12 hours daylight / 12 hours darkness.

Xanthorrhoea preissii can be seen growing in the Temperate House at Kew.

Specimens of wood, trunk and resin from X. preissii are held in the Economic Botany Collection, and are available to researchers by appointment.

In 2011, Kew and the British Museum brought to the heart of London a landscape showcasing the rich biodiversity of Australia, and how these fragile systems are under threat from land usage and climate change.

Xanthorrhoea preissii (balga) was one of 12 star plants featured in the Landscape, which took you on a journey across a whole continent, from eastern Australia’s coastal habitat, through the arid red centre, to the western Australian granite outcrop featuring unique and highly endangered plants.

Australia Landscape was part of the Australian season at the British Museum.
Supported by Rio Tinto.

Read Kew's Australia Landscape blog

View photos of the work that went into the creation and building of the Landscape

Find out more about the other star plants in the Landscape.

Search Kew’s science databases for further information on this species

Xanthorrhoea preissii occurs in the South West Australian Floristic Region (SWAFR), one of the world’s biodiversity hotspots and oldest landscapes. Find out more about Kew’s work in this region and other old landscapes of the world.

The Western Australian Government has a website dedicated to the flora of the region. See the entry for Xanthorrhoea preissii.