Acacias are from the mimosa subfamily, which is itself part of the Fabaceae family. Fabaceaes are legumes and acacias have the typical pods which split to release hard seeds. The greater percentage of acacia species are found in Australia but acacias are also found in the tropical Americas, Africa, Asia and islands of the Pacific and Indian Oceans. The flowers are very small but crowded into spikes and globular heads. The brilliant white, cream, yellow or orange flower heads make an attractive display.
The acacia or wattle as it is commonly known is the floral emblem of Australia. Acacia pycnantha or Golden Wattle is the species most often used to depict the emblem. It is an adaptable variety and is a favourite with birds and insects, providing nectar and seeds in ample quantities.
The acacia converts nitrogen from the air into soil nitrogen. Most are quite hardy. Under ideal, temperate conditions, the acacia can become an environmental nuisance.Most need well-draining soil and full sun. They are generally regarded as short-lived. Propagation is mostly by seed.
Acacias range from prostrate, spreading plants to small and large shrubs through to large forest trees.
Acacia aculeatissima or thin-leaf wattle is a prostrate form which spreads to 2 metres. It has an open habit with slightly prickly foliage. The flower heads are pale to bright yellow and appear from June to November. It is an adaptable low wattle which likes well-drained soil and partial or filtered sun. It can be grown in sand or gravel soils and is drought tolerant. It will also adapt to protected sites in coastal gardens and it is not affected by frost.
Another prostrate wattle is Acacia pravissima ‘Golden Carpet’. This is the prostrate form of Ovens wattle and has a profuse display of bright yellow flower heads. It is a hardy plant which tolerates both dry and moist conditions. If it is to retain the prostrate habit it needs to be propagated from cuttings. It will spread to about 5 metres.
The Gold Dust Wattle (Acacia acinacea or Acacia rotundifolia) is a shapely shrub which is native to semi-arid, open woodlands. It has arching branches and is adaptable to a wide range of conditions providing drainage is good. It has small oblong or oval phyllodes to around 2.5cm long and deep golden globular flower heads. The pods are curved and spirally coiled. The variety ‘Red Tips’ (or ‘Ruby Tips’) has bright red new growth.
Acacia boormanii or Snowy River wattle comes from the Snowy River region of south-eastern Australia. It is an erect, bushy shrub with slender branches and narrow, grey-green phyllodes. The flowers are bright yellow balls. It will tolerate wet periods and makes a good windbreak or screening plant. It is frost tolerant and will grow in a variety of soil types.
Acacia acuminata is known as the ‘jam tree’ in its native Western Australia. The freshly cut wood smells like raspberry jam hence the name. It is a quick growing small tree with narrow foliage and bright yellow, rod-like flower-heads produced from July to October. It likes well-drained soils and a sunny position. Once used for fence posts, Acacia acuminata has again come into prominence over recent years as it is used as a host tree for commercial plantations of sandalwood. The quandong, like the sandalwood, is also a root parasite and favours the jam tree as a host.
Acacia jibberdingensis is a medium to tall shrub with long, narrow phyllodes. It is very showy during the long flowering season with deep yellow, rod-shaped flowers. Acacia calamifolia (Wallowa) is of a similar size and is drought tolerant. It too has profuse, golden globular flower heads. It is a striking shrub and makes a good screening plant. Acacia ligulata (Umbrella Bush) is hardy and decorative. It is bushy from the ground up and makes a
good screening choice.
If your soil doesn’t drain so well, Acacia stenophylla would be a good selection. This small to medium tree has pendulous foliage and cream to yellow flowers. It is frost resistant and does well in coastal gardens if afforded some protection from salt winds and spray. The Myrtle wattle is an excellent option if you wish to attract parrots and pigeons to your garden. Its seeds are a favourite with birds. It often has attractive, reddish stems but is not always long-lived.
Larger acacias that are well worth growing include Acacia decora or western silver wattle. This is very adaptable provided drainage is good. The box-leaf wattle (Acacia buxifolia) is also hardy and flowers profusely from July to December. It can be used for many ornamental and landscape purposes. The Golden Rain wattle (Acacia prominens) grows dense and tall and is useful as a shade, screen or windbreak tree.
Acacia redolens is an excellent screening plant and is also available in a low, spreading form. As a hedging plant, it would be hard to find better than Acacia fimbriata or fringed wattle. It has dense clusters of pleasantly perfumed bright yellow flowers.
With over 1,200 species, there is an acacia to suit every garden and every situation. Your nurseryman will be able to help choose one to suit your requirements.