Acacia longifolia

The narrow, flattened phyllodes are the most useful field mark. They are straight or slightly curved, usually 4 to 25 cm long and 1 to 3.5 cm wide, with two to four prominent veins and a gland 3 to 8 mm above the base.

The branchlets are smooth, and the bark is grey and smooth or finely fissured. The plant typically grows 1 to 10 meters tall.

The flowers are golden yellow, sometimes paler, and grow in one or two mostly stalkless spikes 2 to 5 cm long in the leaf axils. The pods are mostly cylindrical, straight to strongly twisted, 5 to 15 cm long and 3 to 6 mm wide, with a thin, leathery or papery texture that turns brittle when dry.

The seeds are elliptic, 4 to 6 mm long and shiny, with a large, skirt-like aril.

Sydney golden wattle is native to southeastern Australia, from the extreme southeast of Queensland through eastern New South Wales, Victoria, southeastern South Australia and Tasmania. In New South Wales it is common on the tablelands and along the coast.

The plant grows in a variety of habitats there, including foredunes, sclerophyll woodland, and coastal heath and scrub. In South Australia it occurs on the Eyre, Yorke and Kangaroo Island peninsulas and in the southern Mount Lofty Ranges, and across the south-east it is mostly restricted to sand dunes. In Tasmania a subspecies, sophorae, grows in coastal sand dunes.

Outside its native range, the species has become naturalized in coastal areas of southwestern Western Australia, from around Perth in the north to around Albany in the south. It is thought to have spread from escapes from gardens or from revegetation plantings.

It has also established in many countries outside Australia, including New Zealand, South Africa, Portugal, Spain, Italy and India.

Sydney golden wattle is a perennial that grows rapidly. It is a shrub or erect, spreading tree, typically 1 to 10 meters tall, and it reaches a mature height of about 6.1 meters.

Its growth is fast enough that it is used where quick cover is needed. Its branchlets stay smooth throughout its life.

Insects visit the flowers, including bees, wasps, flies, beetles and butterflies, but these visits do not make them pollinators.

The plant's main parasites include a wasp, Trichilogaster acaciaelongifoliae, and the bacterium Agrobacterium tumefaciens.

The species grows in sand dunes, sclerophyll woodland and coastal heath, where it helps hold loose sand in place.

Sydney golden wattle tolerates a range of conditions. It grows in soils with a pH from about 6 to 8.3 and copes with many soil types.

The plant handles both shade and drought well, and it is frost hardy, surviving temperatures down to about -10 degrees Celsius. It suits low-maintenance sites such as road batters, and it is valued as a hedge or screening plant.

It is regarded as a hardy, fast-growing species that is suitable for hydroseeding on banks to stabilize soil.

Sydney golden wattle is widely cultivated in subtropical regions. It is planted to prevent soil erosion and to secure uninhabited sand in coastal areas, mainly where hard frosts are rare.

People have used its parts in several ways. The flowers yield a yellow dye, the pods yield a green dye, and the wood and bark have modest uses, with the bark used in tanning, mainly for sheepskin. In Tasmania, ripening pods and seeds were eaten.

In Southern California it is widely used as a street canopy tree. It grows quickly, reaching about five meters within a year or two of planting, and tolerates drought and heavy pruning.