Brigalow, Brigalow Spearwood, Orkor
Brigalow is common in inland areas from central Queensland to north-central New South Wales. It mainly occurs between latitudes 21-30o S and altitudes 120-330 m (NSW, QLD)
A nitrogen-fixing shrub or medium sized tree usually 12-20 m tall. Phyllodes are curved, tapering to each end, 10-23 cm long and 7-20 mm wide, and silver grey in colour. Golden yellow flower heads are clustered on a common stalk in leaf axils. The reddish brown pod is 7-12 cm long, 5-8 mm wide and indented between the seeds. Flower production is irregular, influenced by climatic conditions, and seed is not set every year. Flowering is mainly in July - September. There are about 19 000 viable seeds per kilogram and seed viability is lost quickly unless the seeds are stored at low temperature. The seed has a thin seed coat and does not require any pre-treatment to promote germination.
Ecology/Way of Life:
Brigalow is found in warm, subhumid and semi-arid climatic zones. Summers can be very hot but there are some winter frosts. Annual rainfall is 500-750 mm throughout most of its distribution but there is high variability from year to year. Rain falls mainly in summer and there is a dry season of 5-7 months. It grows on wide flats, plains and gentle undulating lowlands rarely extending to hill-slopes and ridges. The soils are mainly heavy clays, often alkaline or saline, and usually quite deep. Brigalow dominates open forest communities in wetter areas and is very common in woodlands and low open woodlands in drier areas. Casuarina cristata (commonly called Belah) is a common associate in the north, and in drier areas Brigalow may be equally dominant with other acacias such as Acacia cambagei and Acacia excelsa.
Interaction with Humans/Threats:
The hard, heavy and strong timber makes a good fuel, a high quality charcoal and can be used for posts, poles and some forms of joinery. The heartwood resists decay and termites. Its foliage may be eaten by sheep and cattle when other forage is unavailable but it is not regarded a good fodder tree. This acacia is excellent for shade, shelter and ornamental purposes. Lack of seed and a slow growth rate may limit its use. It reproduces from root suckers and once established it is not easily eradicated.
Other Comments:Acacia harpophylla was named in 1864 by Ferdinand J.H. von Mueller, Government Botanist of Victoria. The genus name is from the Greek akakia = a thorny plant, specifically Acacia arabica; the species name is also from Greek, where harpe= sickle; and phyllon = a leaf, referring to the curved sickle-shaped phyllodes).
Doran, J.C. and Turnbull, J.W. (eds.) 1997. Australian trees and shrubs; species for land rehabilitation and farm planting in the tropics. ACIAR Monograph no. 24. Australian Centre for International Agricultural Research, Canberra. 384p.
Cunningham,G.M., Mulham, W.E., Milthorpe, P.L and Leigh, J.H. 1981. Plants of western New South Wales. Soil Conservation Service. New South Wales Government Printer, Sydney.
Stanley, T.D. and Ross, E.M. 1983. Flora of south-eastern Queensland.Vol. 1. Queensland Department of Primary Industries. Queensland Government Printer, Brisbane.
Topics:Soils Vegetation types Climatic zones Timber Aboriginal resources Germination Fodder Nitrogen-fixation
Text & map from Australian Trees and Shrubs, courtesy Australian Centre for International Agricultural Research; text edited by J. Turnbull; photo courtesy M. McDonald.
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