Acacia decurrens Willd.
Acacia decurrens Willd.
Black Wattle, Green Wattle
Endemic to N.S.W. chiefly on the coast and tablelands from the Hunter Valley S to the A.C.T.; naturalised in south-western W.A., south-eastern S.A., south-eastern Qld, parts of N.S.W. and A.C.T., Vic. and possibly Tas. The ‘natural’ or native distribution is confused by naturalisation caused by widespread plantings in the past in N.S.W., including the A.C.T. where it is adventive according to N.T.Burbidge & M.Gray, Fl. Austral. Cap. Terr. 204 (1970).
Tall shrub to tree to 10 (–15) m high. Bark smooth or fissured, brown, greyish black or black, with conspicuous internodal flange marks. Branchlets with winged ridges 0.5–2 mm high, glabrous or sparsely appressed-puberulous. Young foliage-tips light green or greenish yellow to yellow when pubescent. Leaves dark green; petiole above pulvinus (0.7–) 1.5–2.8 cm long, angular, with a prominent orbicular gland mostly at base of or to c. 7 mm below basal pinnae; rachis 2–12 cm long, angular, furrowed, with orbicular jugary glands at all pairs of pinnae; interjugary glands absent; pinnae 3–13 pairs, (2.5–) 4–7 (–9) cm long; pinnules 15–45 pairs, widely spaced, linear, 5–15 mm long, 0.4–0.8 mm wide, glabrous or rarely sparsely appressed-ciliate, obtuse or subacute. Inflorescences in axillary elongated racemes or terminal false-panicles; peduncles 3–7 mm long. Heads globular, 20–32-flowered, golden. Pods straight-sided to irregularly and mostly slightly constricted between seeds, 2–10.5 cm long, 4–8.5 mm wide, subcoriaceous, smooth, brown or dark brown, glabrous.
Flowers mostly July–Sept.; fruits Nov.–Jan.
Grows in open forest or woodland, on hillsides or gullies, usually on shale.
W.A.: Burekup, Bunbury to Brunswick, G.J.Keighery 9104 (NSW, PERTH). S.A.: Basket Ra., H.van Dam 208 (AD, NSW). Qld: a few miles S of Toowoomba, L.S.Smith 10241 (BRI, NSW). N.S.W.: Menai, P.Hind 5713 & G.D’Aubert (MEL, MO, NSW); 9.5 km SW of junction with Tarago–Goulburn road, L.Thomson 117 (AD, BRI, CANB, K, MEL, NSW, PERTH, US); near Faulconbridge Railway Stn, Blue Mtns, 14 Jan. 1961, M.D.Tindale s.n. (NSW); Old Windsor road–Castle Hill, 30 Aug. 1958, M.D.Tindale s.n. (NSW). A.C.T.: 4.8 km from Queanbeyan on Sutton Rd, H.S.McKee 7348 (NSW). Vic.: Trawalla State Forest, on Western Hwy 0.5 km E of turn-off to Snake Valley, I.C.Clarke 2441 (MEL, NSW).
According to J.H.Ross, Fl. Southern Africa 16: 108 (1975), ‘A decurrens is usually attributed to “(Wendl.) Willd.” with Mimosa decurrens J.C.Wendl., Bot. Beob. 57 (1798), being taken as a basionym. However, Willdenow cites only Mimosa decurrens Donn, Hort. Cant. 1: 114 (1796) which is a nomen nudum. As he provided no reference to Wendland, either direct or indirect, Willdenow’s binomial must be treated as a new name.’
Acacia decurrens was introduced to South Africa, where it has played an important role in the tanning bark industry. The bark has a high tannin yield but not as high as A. mearnsii (q.v.). Hybrids between A. baileyana and A. decurrens are common. Further information on the biological and ecological features, and the utilisation potential, of this species is given in B.R.Maslin and M.W.McDonald, AcaciaSearch: Evaluation of Acacia as a woody crop option for southern Australia, RIRDC Publication No. 03/017, 68–75 (2004).
Data derived from Flora of Australia Volumes 11A (2001), 11B (2001) and 12 (1998), products of ABRS, ©Commonwealth of Australia
Minor edits by B.R.Maslin & J.Reid
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