A fast growing, nitrogen fixing tree to 6 - 10 m. It is adapted to a wide range of sites receiving 600 - 925 mm rainfall and at altitudes from near sea - level to 200 m. Native to south - eastern Australia.
Black wattle occurs in the understorey of tall, open forest dominated by eucalypts. It can form dense thickets where it has recolonised cleared land. Its native companions include Eucalyptus saligna, Eucalyptus bosistoana, Eucalyptus muellerana, Eucalyptus ovata, Eucalyptus globulus, Eucalyptus viminalis, Eucalyptus cypellocarpa, Eucalyptus radiata and Eucalyptus smithii.
The leaves have a high protein content (15%) but palatability trials with sheep showed milled leaves to be unpalatable on their own. It has been fed to cattle in Hawaii in drought periods. It is an efficient nitrogen fixer and is an ideal tree for regenerating impoverished soils. In Indone-sia where the tree is used extensively, it is found to yield 21 - 28 t/ha/yr of wet leaves, contain-ing 240 - 285 kg of nitrogen. Indonesian farmers claim that vegetables and tobacco grown in rotation with A. mearnsii give twice the yield because of the green manure the trees provide.
It yields high quality tannin (36 - 44% ) from the bark; the powdered bark extract is used to prepare tannin formaldehyde adhesives for exterior grade plywood, particle board and timber.
The wood is hard, but is moderately easy to work, and takes a good polish. The wood is used for house poles, mine timbers, tool handles, cabinet making, joinery, flooring, construction timber, matchwood and hardboard. It is used for rayon pulp arid paper pulp, although the hard wood makes chipping expensive. It has good strength characteristics for wrapping paper, and is an excellent fuel wood and charcoal.
It is cultivated in India, South Africa, eastern Africa and South America. South African plantations cover 160,000 hectares, and there are over 125,000 hectares in Brazil. This acacia is probably the best example of an Australian tree which is used extensively overseas but almost ignored in its homeland.