Acacia - or Wattle. To celebrate Wattle Day, September 1st.

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Have you ever wondered why our national colours are green and gold? Australia's National Floral Emblem, seen on Australia’s Coat of Arms, is Acacia pycnantha, the Golden Wattle and it is the green and gold colours of the foliage and flowers that provide Australia's official colours.
The genus Acacia belongs to the family Fabaceae (previously Mimosaceae). There are about 1350 species of Acacia found throughout the world in Australia, Africa, Madagascar, throughout the Asia - Pacific region and in the Americas. Nearly 1000 species of Acacia are found in Australia where it forms the largest genus of our flowering plants.

In Australia the common name of Wattle developed from a plant that the early convicts and colonists around Sydney called black wattle (although the plant in question was not actually a wattle). The branches of this shrub were used to build the walls of their huts. The branches were woven to form a rough framework that was then daubed over with mud to make a more permanent structure. This "wattle and daub' building method is the oldest known method for making a weatherproof structure and was used as far back as the Iron Age (1100 BC).
Acacias grow over vast areas of Australia and occupy a wide range of differing habitats from coastal to sub-alpine regions and from high rainfall to arid inland areas. They are particularly common in the arid and semi-arid and the dry sub-tropical regions of the country where mulga is dominant over huge areas.
Australian acacias are generally small to large shrubs, but there are a few which in high rainfall areas grow into large trees, eg Acacia melanoxylon (Blackwood) and Acacia dealbata (Silver Wattle). Surprisingly, one of the larger growing species is Acacia peuce (Waddy Wood) that is only known from two locations on the edge of the Simpson Desert. Other desert acacias include Mulga (Acacia aneura) and Gidgee (Acacia cambagei).
Acacias have a range of foliage types while the colour of both leaves and phyllodes ranges from light or dark green to blue or silver-grey. The true leaves are divided into leaflets, and the first leaves grown by a wattle seedling will have this fern-like appearance. Some wattles eg Cootamundra wattle, retain these true leaves throughout their life. However a large group of wattles has developed leaf-like structures from flattened and modified stem of the leaf. These are called phyllodes and appear soon after germination. The phyllodes of different species are vary enormously in size and shape.[Image not found]
On the top margin of the phyllode or on the leaf stalk of the fern-like leaves there are usually one or more glands appearing as an indented or raised “pimple”. These are nectar glands that produce small quantities of nectar that attracts insects and some birds.
A few species lack true leaves or phyllodes altogether and in these plants cladodes (or modified stems) function as the leaves. Australian acacias do not have thorns or prickles unlike acacias from other parts of the world.
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Many of us welcome the flowering of wattles as signalling the coming of spring as many species start to flower in late winter. However a wattle can be found in flower somewhere at any time of the year.
The golden "flowers" are actually a head of tiny individual flowers that are clustered together into an inflorescence that is either a globular head or a cylindrical spike. Each inflorescence may comprise from as few as 3 to as many as 130 or more individual flowers. The inflorescences may be solitary or be grouped into large clusters of bloom. Acacia flowers vary in colour through cream, pale yellow to orange and gold. The flowers of many species are sweetly or delicately perfumed and many produce large amounts of pollen, although the flowers don’t produce nectar.
Following flowering, seeds develop in pods that vary in size and shape between species and may be flat or cylindrical, short or elongated. The seeds are attached inside the pod by a seed stalk or aril that contains oils and fats that are relished by ants. After a few weeks of ripening the pods burst open to release the seeds that can then lie dormant in the soil for many years. Ants will carry away the fallen seed, taking the aril plus seed underground to store as a food source. This ant harvesting helps distribute seed as well as storing it until it is released by soil disturbance or fire, when quick vegetation cover is again required.
Acacias are legumes (like the pea-flowered plants) and are able to take-up (or "fix") their nitrogen directly from the atmosphere with the aid of soil bacteria (Rhizobium sp). This occurs in nodules or lumps on the roots of the plants. This ability allows wattles to live in areas of poor soil and to quickly colonise bare areas eg disturbed land along roadsides and in logged forests, where Acacias are one of the first species to reappear.
Acacias are generally quite fast growing, with many of them, especially in wetter areas, not living a long time (maybe 10-20 yrs), although a few species may live longer than fifty years. Conversely desert wattles like mulga have a very slow growth rate but may live to 100 years or more in age, something to think about as we throw another mulga branch on the campfire.
Many Acacia species occur in areas where bushfires are common, such as dry forests, woodlands and arid shrub-lands. In these habitats they are often "pioneer" species, quickly recolonising burnt-out areas and then over time being gradually replaced by other species in the plant community.
Many acacias exude gum from their stems and branches and this, together with the seeds, arils and pollen, forms an important food source for some possums, other small mammals like gliders and small kangaroos, birds and insects.
All parts of many Acacia species have been used by humans for varying purposes. Aborigines ground dried wattle seeds between stones to form a flour which was then baked as a damper. It is thought that Aboriginal people in central Australia have been grinding grass or wattle seed for no more than 4 000 years. Green seeds were also eaten, like green peas. It is currently believed that only desert dwellers ate acacia seeds, with the exception of coastal SA and Tasmanian tribes, who roasted the pods and then ate the seeds of Acacia sophorae (Coast Wattle).
Various extracts from the bark, leaves or phyllodes have been used by Australian Aborigines for a wide variety of medicinal purposes such as relieving toothache or colds or applying to wounds and burns.
The gum from some species is also edible. In colonial days around Sydney gum from Acacia decurrens (Green Wattle) was collected and turned into a kind of chewing gum that was quite popular.
It is only fairly recently that research has begun to determine the nutritional potential of several Acacia species, as well as any toxic effects. Some limited use of Acacia as a food is occurring in the "bush food" industry with, for example, ground Acacia seeds being used as a component of a bread known as "Wattle Damper" and as a flavouring for ice cream.
A feature of many Acacias is their dense hard wood. Some of the heartwoods also have distinct graining and colouring or odours. The Aboriginal people used wood from different species for just about anything that they made out of wood, such as clubs, spears, spear heads, digging sticks, shields, woomeras, boomerangs etc.
Europeans too recognised the value of the wood from some species and used the wood from a few species for cabinet making and ornamental work, including coach building and for beer barrels. Other species were used for such things as gunstocks and even machine bearings, as well as fence posts.
Acacia melanoxylon (Blackwood) is the best known and most highly valued temperate Acacia, producing sought after timber. In Australia, most commercial harvesting of Blackwood is from natural stands in Tasmania. Plantation-grown timber is produced mainly in New Zealand, South Africa and Chile. Blackwood timber is used for construction and furniture, both as solid wood and veneer. In recent years, commercial plantations of Blackwood for timber production have been established in Australia
Tannin has been extracted from the bark of a number of species for use in tanning leather. The most important species include Acacia dealbata (Silver Wattle), A. mearnsii (Black Wattle) and A. pycnantha (Golden Wattle). These species provide commercial returns both in Australia and overseas. The bark of A.mearnsii is valuable in the tanning industries and commercial plantations exist in a number of countries (eg.South Africa, Brazil). Australia actually imports A.mearnsii bark tannin from South Africa where the tree has unfortunately escaped from plantations to become a pest species. Although historically planted for its tannin-rich bark, its wood is also used for paper pulp, cellulose for rayon, charcoal and round timber. In Australia Black Wattle, along with its relative A. dealbata (Silver Wattle), is sometimes harvested from natural stands for paper pulp.
The quick-growing characteristics of many of the larger Acacia species makes them useful for fodder, the control of soil erosion and for providing fuel for cooking and heating. On our travels into drier parts of the country many of us delight in camp fires of mulga (Acacia aneura) wood, or despair as the sharp points of old roots stake our tyres. Mulga has also provided many graziers with emergency drought fodder, although its nutritional status is not high. The trees must be felled or pushed over so stock can reach the foliage and seed pods. When rain falls the mulga will quickly regrow.
Prickly acacia, a native of Pakistan was introduced into Queensland in the early 1900s for shade and fodder. Unfortunately it is now regarded as one of the worst weeds in Australia because of its invasivness, potential for spread, and economic and environmental impacts. At present millions of hectares of arid and semi-arid land across northern Australia are infested with prickly acacia, mainly in the Mitchell Grass Downs. Prickly acacia could potentially infest vast tracts of grasslands and woodlands throughout Australia.
Wattles have been so significant to our social and economic development that we have a special day to celebrate them. Wattle Day, with its long history is celebrated on the 1st of September each year. In 1889 the formation of a Wattle Blossom League in SA was proposed, aiming to "promote a national patriotic sentiment among the woman of Australia" by wearing sprigs of wattle on all official occasions. The group inspired the formation of a Wattle Club in Melbourne. During the 1890s people went into the country on September 1 each year to view the wattles.
The concept of Wattle Day spread to New South Wales and the first Wattle Day was held on September 1, 1910 in Sydney, Melbourne and Adelaide. On that day the Adelaide committee sent sprigs of Acacia pycnantha to the Governor and other notables in Adelaide. It was this Acacia that become accepted as the official national floral emblem.
The celebration of Wattle Day reached its height during World War 1. The day was a focus for fund raising for the war effort. Many trees were denuded to supply the sprigs of wattle sold on that day. Boxes of wattle were sent to soldiers in hospitals and a sprig of wattle was enclosed in letters to soldiers to remind them of home. After the war celebration of Wattle Day was continued in schools.

Although the date of Wattle Day has been changed many times it is currently set for September 1st.