Northern Wattle, Thick-podded Salwood
This acacia occurs in the lowland tropics in north-eastern Queensland, south-western Papua New Guinea and south-eastern Irian Jaya, Indonesia. The latitudinal range is 8-20o S and it occurs mainly below 200 m altitude. (QLD)
A very fast-growing, nitrogen-fixing tree, rarely exceeding 15 m in height and bushy in form in Queensland but up to 30 m and with a single stem in Papua New Guinea. The bark is hard with deep vertical furrows. Phyllodes are smooth, grey-green, curved, 11-22 cm long and 10-40 mm wide with numerous longitudinal nerves. Flowers are bright yellow in spikes, 4-7 cm long, on thick stalks, clustered in groups of 2-6 in leaf axils. Pods are dull brown, oblong, woody, flat or twisted, 5-8 cm long by 2-4 cm wide, with oblique veins. The main flowering period is May - June and pods mature in October - November. There are about 36 000 viable seeds per kilogram. Seeds need pre-treatment with boiling water for one minute to promote germination.
Ecology/Way of Life:
The Northern Wattle is found in warm to hot, humid and sub-humid zones with a mean annual rainfall of 1000-3500 mm. Rainfall follows a monsoonal pattern. The entire range is frost-free. In Australia it is commonly found behind coastal foredunes, on slopes of stabilised sand dunes, and on coastal plains and foothills. In New Guinea it occurs on the gently undulating alluvial plain of the Oriomo Plateau. It is found mainly on well-drained, strongly acidic, infertile soils but also on poorly drained soils subject to flooding. In Queensland it occurs in the understorey of open forest or open woodland dominated by Eucalyptus pellita, E. tessellaris or E. tereticornis and in low woodland near the beach adjacent to Casuarina equisetifolia. In Papua New Guinea and Indonesia it commonly fringes swamps associated with Acacia auriculiformis, A. leptocarpa, A. mangium, Melaleuca spp. and Lophostemon suaveolens.
Interaction with Humans/Threats:
The wood is golden brown, strong and durable and moderately heavy. It has been used for heavy construction, furniture, boat building, flooring and veneer. Acacia crassicarpa is one of the fastest growing of the tropical acacias and large areas of it have been planted in Sumatra, Indonesia to provide paper pulp. It shows promise for rehabilitating tin-mining sites in Malaysia. Care must be taken to choose appropriate seed sources because of the variation that exists throughout its range.
Other Comments:Acacia crassicarpa was named in 1842 by explorer and botanist Allan Cunningham, based on the Greek akakia = a thorny plant, specifically Acacia arabica; the species name is based on the Latin crassus = thick, and carpus = fruit, referring to the thick pod).
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.
Maslin, B.R. and McDonald, M.W. 1996. A key to useful Australian acacias for the seasonally dry tropics. Western Australian Herbarium, Department of Conservation and Land Management, Bentley, Western Australia and Australian Tree Seed Centre, CSIRO Forestry anf Forest Products, Canberra. 80p.
Thomson, L.A.J. 1994 Acacia aulacocarpa, A. cincinnata, A. crassicarpa and A. wetarensis: an annotated bibliography. Australian Tree Seed Centre, CSIRO Division of Forestry, Canberra. 131p.
Topics:Soils Germination Vegetation types Timber Firewood Nitrogen-fixation
Text & map from Australian Trees and Shrubs, courtesy Australian Centre for International Agricultural Research; text edited by J. Turnbull; photo courtesy B. Gunn.
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