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Photographer: B.R. Maslin
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Photographer: B.R. Maslin
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Seed from one herbarium voucher. Scale in mm. Photographer: F. McCallum.
Botanical name
Acacia pruinocarpa Tindale, Contr. New South Wales Natl Herb. 4: 73 (1968)
Common name
Western Gidgee (preferred common name), Christmas Wattle (Hamersley Range area), Southern Gidgee, Black Gidgee, Black Wattle and Gidgee
Aboriginal name
Burlurru or Burluru (Ngarluma and Yindjibarndi), Jilpajilpa (Nyangumarta), Marlkan (Kariyarra), Bulurru (Banyjima), Ngalkurra (Putijarra) and Yallari, Yalari, Bulluru or Pulurru (Kurrama)
Description
Handsome trees commonly 5-6 m but on favourable sites may attain 12 m, with a single trunk (bole may reach 6 m long) or sparingly branched near ground level into a few main trunks, trunks straight or somewhat crooked, crowns spreading and dense or relatively open, frequently with a rounded habit when young, readily suckers if roots are disturbed. Bark grey or dark brown, rough on main trunks, otherwise smooth. Branchlets glabrous, often pruinose. New shoots bright green. Phyllodes linear to very narrowly elliptic, 6-17 (-22) cm long, (5-) 6-20 (-30) mm wide, somewhat thick and leathery, normally wide-spreading, straight or shallowly recurved, glabrous, sub-glaucous (glaucous on young plants); with a single, prominent, longitudinal central nerve ; lateral nerves obscure; the marginal nerves prominent; apex obtuse to sub-acute. Glands 2-5 along the upper margin, small, the largest being at the base of the phyllode. Inflorescences 6-20-headed racemes 3-15 cm long, the raceme axes stout, often pruinose and glabrous; peduncles 10-40 mm long, mostly grouped 2 or 3 together along raceme axes, glabrous; heads globular, 7-9 mm in diameter when dry, bright light golden, very showy, densely 55-100-flowered. Flowers 5-merous; sepals united; bracteole laminae and sepal apices densely golden-hairy. Pods oblong to narrowly oblong, flat but raised over the seeds along the midline, not constricted between seeds, 3-12 cm long, 9-17 mm wide, rather papery, glabrous, pale brown, pruinose. Seeds transverse to oblique in the pods, ovoid to obloid-ellipsoid or sub-rounded, 5-6 mm long, 4-4.5 mm wide, not shiny, black; funicle short and flat, aril small.
Characteristic features
Tree or large coppicing shrub growth form. Branchlets glabrous and often pruinose. Phyllodes rather large (mostly 6-17 cm x 6-20 mm) and leathery, sub-glaucous (glaucous on young plants), normally wide-spreading, prominently 1-nerved. Inflorescences long-racemose (racemes 3-15 cm); peduncles long (10-40 mm); heads globular, very showy, densely 55-100-flowered, flowering in late spring and summer. Pods narrowly oblong, broad (9-17 mm), flat but raised over the seeds along the midline, rather papery, pale brown, pruinose. Seeds transverse to oblique in the pods.
Distribution and ecology
Occurs in arid areas from the Pilbara and Ashburton-Murchison regions in Western Australia eastwards to far northwestern South Australia and west-central Northern Territory. Within the Pilbara it is mostly found from the Fortescue River southwards, however, there are scattered occurrences north to Nullagine and the Abydos - Woodstock Aboriginal Pastoral Reserve. Throughout its extensive geographic range Western Gidgee grows in a variety of topographic situations but, as in the Pilbara, it is commonly found on rocky hills and Mulga plains in shallow loam or clay over rock or hardpan, often with a soft spinifex understorey; it also occurs alluvial washes associated with drainage lines. Further ecological details are provided by Turnbull (1986). Western Gidgee is often not uncommon in the places where it grows but commonly occurs as scattered individual plants; it sometimes forms moderately dense stands of widely spaced individuals.
Flowering and fruiting period
Flowers from October to December. This species produces a profusion of large golden heads and because it is one of the few Pilbara Wattles that flowers in summer months it is conspicuous in the landscape at that time of the year. Because of the paucity of mature fruiting specimens it is difficult to accurately determine the fruiting period. Pods with mature seeds have been collected in January, March and from June to October. The pods collected in the June-October period were possibly collected from the ground under the plants and if so it is not known if this seed was simply retained in pods that had dropped many months earlier.
Variation
This species is generally reasonably invariate. However, a few plants with unusually narrow and long phyllodes (about 5 mm wide and to up to 22 cm long) have been recorded from a population of typical A. pruinocarpa near Tom Price (E. Thoma, pers. comm.).
Affinities
Most closely allied to A. ensifolia (a Queensland species).
Notes
A slow-growing species that both coppices from the base and produce root suckers following damage; it readily resprouts from the roots when they are disturbed. Western Gidgee is fire tolerant and will sprout from rootstock just outside the intact canopy after a burn. As with A. pachyacra the seeds have a high propensity to germinate without any formal removal of a dominancy mechanism (Fox and Dunlop 1983).
An attractive tree which is well suited for shade and ornamental purposes in inland areas but its root-suckering may possibly constrain its horticultural use.
The wood is an attractive dark ebony colour, has a high density and as such has potential for use in furniture manufacture, as a craft wood and for musical instruments (Hill and Brennan 2000). However, it is very susceptible to attract by borers and quickly rots once such damage occurs.
The foliage is readily eaten by sheep and cattle during periods of feed shortage but the foliage is often out of reach of the stock; contains about 13% crude protein and is high in total minerals (Mitchell and Wilcox 1994).
As reported by Juluwarlu Aboriginal Corporation (2003) and by Young (2007) indigenous peoples of the Pilbara burn then grind the ash (jurnpa) from young dry stems and phyllodes of A. pruinocarpa and combine this with chewing tobacco to make burrgu or pulkurr, a mixture which acts as a stimulant; ash from burnt wood was also used with native tobacco (Nicotiana species) as a chewing quid. This species is a source of a sweet, edible gum (gardangu or ngarkarla) and the root may contain edible grubs (pilu or nyamirla). This species, however, is not renowned for large gum production; the chemical characterisation of its gum is provided by Anderson and McDougal (1988).
Conservation status
Not considered rare or endangered.
Origin of name
The botanical name is derived from the Latin pruina (hoarfrost) and the Greek karpos (fruit) and alludes to the white powdery substance (pruinosity) that appears on the surface of the pods.
References
Anderson, D.M.W. and McDougal, F.J. (1988). Chemical characterization of the gum exudates from eight Australian Acacia species of the series Phyllodineae. Food Hydrocolloides 2(4): 329-336.
Fox, J.E.D. and Dunlop, J.N. (1983). Acacia species of the Hamersley Ranges, Pilbara Region of Western Australia. Mulga Research Centre. Occasional Report No. 3. pp. 94. (Western Australian Institute of Technology: Bentley.)
Hill, P. and Brennan, G.K. (2000). Wood properties of southern gidgee (Acacia pruinocarpa) from different sites in the Pilbara and goldfields regions of Western Australia. CALM Science 3(3): 317-322.
Juluwarlu Aboriginal Corporation (2003). Wanggalili: Yindjibarndi and Ngarluma Plants. pp. 128. (Juluwarlu Aboriginal Corporation: Roebourne, Western Australia.)
Mitchell, A.A. and Wilcox, D.G. (1994). Arid shrubland plants of Western Australia. Edn. 2. pp. 478. (University of Western Australia Press in association with the Department of Agriculture: Perth.)
Turnbull, J.W. (ed.) (1986). Multipurpose Australian trees and shrubs: lesser-known species for fuelwood and agroforestry. pp. 316. (Australian Centre for International Agricultural Research: Canberra.)
Young, L. (2007). Lola Young: Medicine Woman and Teacher. Complied by Anna Vitenbergs. pp. 160. (Fremantle Arts Centre Press: Fremantle.)