Acacia is the largest genus in the family Mimosaceae, the Mimosa family, which is mainly tropical and sub-tropical in distribution.
Acacia pycnantha, Golden Wattle, is a shrub or small tree about 4 to 8 metres tall. After the seedling stage, true leaves are absent, their function being performed by phyllodes which are modified flattened leaf stalks lacking leaf blades. The leathery phyllodes are 6 to 20 cm long, broadly lance or sickle-shaped and bright green in colour. In spring large fluffy golden-yellow flower-heads with up to eighty minute sweetly scented flowers provide a vivid contrast with the foliage. The dark brown mature fruit, 7 to 12 cm long, splits along one side to release the seeds.
Golden Wattle occurs in the understorey of open forest or woodland and in open scrub formations in South Australia, Victoria, New South Wales and the Australian Capital Territory, in temperate regions with mean annual rainfall of 350 mm to 1000 mm. It has been introduced into the Stirling Ranges near Perth where it threatens to become weedy. It regenerates freely after fires, which usually kill the parent plants but stimulate the germination of seeds stored in the soil if rain follows soon after. Regeneration may produce dense thickets in forests and woodlands and along roadsides.
The brilliant yellow, fragrant flowers of Golden Wattle make it a popular garden plant. It is moderately frost tolerant and grows well in a wide range of soils provided drainage is effective, but tends to be short-lived in cultivation. It is easily propagated from seed soaked in hot water to break the hard seed coat, and the seedlings can be transplanted to pots of soil mix for growing on before planting out in a lightly shaded or open position.
Golden Wattle is grown abroad in temperate regions for its bark which has a higher content of tannin than other species of Acacia cultivated for tanbark, although its relatively small size reduces the overall yield. Golden Wattle flowers have been used in perfume making. It was introduced to horticulture in the northern hemisphere about the middle of the nineteenth century. In Britain it survives outdoors only in the mildest areas. In California it has escaped from garden cultivation and now grows wild but it is not considered a pest. In South Africa, however, it has become a significant weed species.