Acacia falcinella Meisn.
Acacia pycnantha, commonly known as the golden wattle, is a tree of the family Mimosaceae native to southern Australia. It flowers in late winter and spring, producing a mass of fragrant, fluffy, golden flowers. It is the official Floral Emblem of Australia.
Acacia pycnantha generally grows as a small tree to between 3 and 8 metres (10-25 ft) in height, though trees of up to 12 m high have been reported in Morocco. The bark is generally smooth, dark brown to grey, while branchlets may be glabrous or covered with a white bloom. The mature trees do not have true leaves but have long, sickle-shaped phyllodes that hang down from the branches. Shiny and dark green, these are between 9 and 15 cm long, 1 to 3.5 cm wide and falcate to oblanceolate in shape. New growth has a bronze coloration. Flowering usually takes place from July to November in the species' native range. The rounded inflorescences are bright yellow and occur in groups of 40 to 80 in axillary 2.5-9 cm-long racemes. Each inflorescence is made up of 50 to 100 tiny flowers. The later developing pods are flattish, straight or slightly curved, 5 to 14 cm long and 0.5 to 0.8 cm wide.
Species similar in appearance include mountain hickory wattle (A. obliquinervia), A. leiophylla and orange wattle (A. saligna). A. obliquinervia has grey-green phyllodes, fewer flowers in its flower heads, and broader (1.25-2.5 cm-wide) seed pods. A. leiophylla has paler phyllodes.
Acacia pycnantha was first formally described by botanist George Bentham in the London Journal of Botany in 1842. The type specimen was collected by the explorer Thomas Mitchell in present-day northern Victoria between Pyramid Hill and the Loddon River. Bentham thought it related to Acacia leiophylla, which he described in the same paper. The specific epithet pycnantha is derived from the Greek words pyknos (dense) and anthos (flowers), a reference to the dense cluster of flowers that make up the globular inflorescences. Queensland botanist Les Pedley reclassified the species as Racosperma pycnanthum in 2003, in his proposal to reclassify almost all Australian members of the genus into the new genus Racosperma, however this name is treated as a synonym of its original name.
Other synonyms include:
- Acacia falcinella Meisn.
- Acacia petiolaris Lehm.
- Acacia pycnantha var. petiolaris H.Vilm.
- Acacia pycnantha Benth. var. pycnantha
- Acacia westonii Maiden
Other common names recorded include green wattle, black wattle, witch and broad-leaved wattle.
Hybrids of the species are known in nature and cultivation. In the Whipstick forest near Bendigo in Victoria, putative hybrids with Acacia williamsonii have been identified; these resemble Acacia hakeoides. Garden hybrids with Acacia podalyriifolia raised in Europe have been given the names Acacia x siebertiana and Acacia x deneufvillei.
Distribution and habitat
Golden wattle occurs in south-eastern Australia from South Australia’s southern Eyre Peninsula into western Victoria and northwards into inland areas of southern New South Wales and the Australian Capital Territory. It is found in the understorey of open eucalypt forests on dry, shallow soils. Cultivars outside Australia have been attacked by dormant pests, leading the Australian Invasive Species Council to demand action to be taken in case the pests reach Australia.
The species has become naturalised beyond its original range in Australia. In New South Wales it is especially prevalent around Sydney and the Central Coast region. In Tasmania it has spread in the east of the state and become problematic in bushland near Hobart. In Western Australia, it is found in the Darling Range and western wheatbelt as well as Esperance and Kalgoorlie.
Outside Australia it has become naturalised in South Africa, Tanzania, Italy, Portugal, Sardinia, India, Indonesia, New Zealand and California. The gall-forming wasp Trichilogaster signiventris has been introduced in South Africa for biological control and has reduced the capacity of trees to reproduce throughout their range.
The wood serves as food for larvae of the jewel beetle species Agrilus australasiae. The larvae of a number of butterfly species feed on the foliage including the fiery jewel, icilius blue, lithocroa blue and wattle blue.
On the phyllodes are located nectaries, which produce nectar that birds feed upon just before or during flowering. These only become active on phyllodes near flowers. While feeding, birds brush against the flower heads and dislodge pollen. Several species of honeyeater, including the white-naped, yellow-faced, New Holland,, and occasionally white-plumed and crescent honeyeaters as well as the silvereye have been observed foraging in this way.
Golden wattle has been grown in temperate regions around the world for the tannin in its bark, which provides the highest yield of all the wattles. Trees can be harvested for tannin from seven to ten years of age. Commercial use of its timber is limited by the small size of trees, but is has high value as a fuel wood. The scented flowers have been used for perfume making, and honey production in humid areas. However, the pollen is too dry to be collected by bees in dry climates. In southern Europe, it is one of several species grown for the cut-flower trade and sold as "mimosa". Like many other species of wattle, Acacia pycnantha exudes gum when stressed. It was eaten by indigenous Australians and has been investigated as a possible alternative to gum arabic, commonly used in the food industry. Trees can be planted with the taller Eucalyptus cladocalyx for a two-layered windbreak.
Golden wattle is cultivated in Australia and was introduced to the northern hemisphere in the mid-1800s. Although it is short lived, it is widely grown for its bright yellow, fragrant flowers. As well as being an ornamental plant, it can be used as a windbreak or in controlling erosion. The species has a degree of frost tolerance and is adaptable to a wide range of soil conditions, however it prefers good drainage. It can suffer yellowing (chlorosis) in limestone-based (alkaline) soils. Highly drought-tolerant, it needs 370 to 550 mm winter rainfall for cultivation. It is vulnerable to gall attack in cultivation. Propagation is from seed which has been pre-soaked in hot water to soften the hard seed coating.
Symbolic and cultural references
Although wattles, and in particular the golden wattle, have been the informal floral emblem of Australia for many years, it was not until Australia’s bicentenary in 1988 that the golden wattle was formally adopted as the floral emblem of Australia. The date of gazettal was 1 September which was marked by a ceremony at the Australian National Botanic Gardens which included the planting of a golden wattle by Hazel Hawke, the Prime Minister’s wife. In 1992, 1 September was formally declared "National Wattle Day".
The Australian Coat of Arms includes a wreath of wattle, however this does not accurately represent a golden wattle. Similarly, the green and gold colours used by Australian international sporting teams were inspired by the colours of wattles in general, rather than the golden wattle specifically.
The species was depicted on a stamp captioned "wattle" as part of a 1959-60 Australian stamp set featuring Australian native flowers. In 1970 a 5c stamp labelled "Golden Wattle" was issued to complement an earlier set depicting the floral emblems of Australia. To mark Australia Day in 1990 a 41c stamp labelled "Acacia pycnantha" was issued. Another stamp labelled "Golden Wattle", with a value of 70c, was issued in 2014. The golden wattle inspired the design and decoration of the Order of Australia which was established in 1975. The crest of the Governor-General of Australia features St. Edward's Crown over a sprig of golden wattle.
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