Xanthorrhoea preissii (synonyms X. pecoris, X. reflexa), with the common name balga, is a widespread species of perennial monocot in Southwest Australia. This plant, and other members of the genus Xanthorrhoea, are also known as grasstrees. The form of the plant resembles a tree, with very long and bunched, grass-like, leaves that emerge from a central base.
The trunk may grow over 3 metres tall, the often blackened appearance is evidence of its ability to withstand fire. The remains of the flammable leaves and the annual regrowth produce banding, allowing the age of the plant to be determined, and giving a record of previous fires in its habitat. The inflorescence appears on an upright spike, 1.5 m to 2.5 m long, between June and December. The sessile flowers, creamy or white, appear more profusely when stimulated by bushfire.
It is found throughout coastal plains, near watercourses, and inland forest regions, in a range extending from Geraldton to Albany and in the Avon Wheatbelt. It occurs on a wide variety of soil types and is sometimes associated with laterite and granite.
The species had a high economic importance to the Noongar people, who named it balga, using the gum it contains, the spike for fish spears, and the bardi grub as a source of food. Anecdotal information on the species refers to an association with fire in the culture of those people. It was first described by Stephan Endlicher in the 1846 volume of Plantae Preissianae. The appearance of the plant was seen as resembling a native inhabitant, holding a spear, by the early settlers of the region; in Western Australia it is commonly referred to as a blackboy.
The species is named as one of the dominant taxa in Corymbia calophylla – Xanthorrhoea preissii woodlands and shrublands of the Swan Coastal Plain, a critically endangered ecological community, once widespread and now restricted to a narrow range. Its occurrence is a characteristic of two other marri (Corymbia calophylla) communities, but the marri/Xanthorrhoea community is distinguished by the drier soils of the communities range along the eastern edge of the Swan Coastal Plain.
- "World Checklist of Selected Plant Families". The Board of Trustees of the Royal Botanic Gardens, Kew. Retrieved 2011-06-27.
- "Xanthorrhoea preissii". FloraBase. Department of Environment and Conservation, Government of Western Australia.
- Ward, D J; Lamont, B B. "Probability of grasstrees (Xanthorrhoea preissii) flowering after fire" (PDF). Journal of the Royal Society of Western Australia (83): 13–16.
- Lehm., Plantae Preissianae 2:39 (1846)
- Gardner, C.A. (1981). Wildflowers of Western Australia. Perth: St George Books. p. 10. ISBN 0-909699-01-1.
- "Corymbia calophylla – Xanthorrhoea preissii woodlands and shrublands of the Swan Coastal Plain.". Threatened species & ecological communities. Department of the Environment, Water, Heritage and the Arts. 19 Feb 2007. Retrieved 2009-05-31.
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