Classification of the genus Acacia (in the wider sense) has been subject to considerable debate. It is generally agreed that there are valid reasons for breaking it up into several distinct genera, but there has been disagreement over the way this should be done. As of 2017, it is widely (but not completely) accepted that the section that includes the majority of the Australian species (including this one) should retain the name Acacia, whilst other sections of the genus should be transferred to the genera Acaciella, Mariosousa, Senegalia and Vachellia[].

Common Name: Mulga Acacia

General Information

Mulga acacia is an evergreen shrub or a tree. In the higher rainfall areas of its range it can become a single stemmed tree growing 10 - 15 metres tall, though on dry locations or on very shallow soils, it is more likely to be a stunted low shrub 2 - 3 metres tall. The bole is usually short, fissured and sometimes twisted[, ]. Although it produces true leaves as a seedling, llike most members of this section of the genus, the mature plant does not have true leaves but has leaf-like flattened stems called phyllodes[].
This species was one of the most important food plants for the native Australians and it is still often gathered from the wild by local people for its many edible, medicinal and other uses. It has been suggested as a potential commercial seed crop for areas such as Western Australia[]. The attractive foliage of the plant has made it a popular ornamental[]. It has been introduced to a number of tropical countries in Asia, Africa and Latin America[].
Acacia aneura is a widespread species occurring in most vegetation communities in inland Australia. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

The seed of many Acacia species, including this one, is edible and highly nutritious, and can be eaten safely as a fairly major part of the diet. Not all species are edible, however, and some can contain moderate levels of toxins[]. Especially when harvesting from the wild, especial care should be taken to ensure correct identification of any plants harvested for food[].
Especially in times of drought, many Acacia species can concentrate high levels of the toxin Hydrogen cyanide in their foliage, making them dangerous for herbivores to eat.

Botanical References

Range

Australia - New South Wales, Queensland, South Australia.

Habitat

Arid areas in all mainland states except Victoria[, ]. A dominant species in open woodland or shrubland in arid and semi-arid zones at elevations from sea level to about 1,000 metres[].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	15.00 m
Pollinators	Bees, Insects
Cultivation Status	Ornamental, Wild

Cultivation Details

A plant of arid and semi-arid areas of the tropics and subtropics, growing naturally at elevations from sea level to about 1,000 metres[]. It is found in areas with an annual rainfall in the range of 100 - 500 mm[]. It its native range it experiences hot summers and cool winters with light frost[]. It has been known to experience occasional temperatures as low as -7°c in its native range[].
Prefers a sandy loam and a very sunny position[]. Succeeds in any good garden soil that is not excessively limey[]. Most species of Acacia become chlorotic on limey soils[]. In the wild this species tolerates periodic inundation[]. Young plants quickly produce a long taproot with an extensive lateral root system in the top 30cm of the soil and, once this is established, they become very drought tolerant[, ].
Growth rate is generally slow, but is related to moisture conditions. In central Australia planted specimens receiving an average of 370mm of rainfall a year grew in ten years into multi-stemmed shrubs 3 metres tall with a bole 2 - 4cm in diameter and with a crown diameter of 2 metres[]. Cultivated specimens receiving regular irrigation have reached 10 metres tall with a bole diameter of 10cm within 10 years[].
In trials where rainfall is relatively high, the Charleville, Queensland provenance, a broad phyllode form, has grown more rapidly than provenances from central Australia[].
Plants are very sensitive to fire, and can also be killed by severe lopping[, ].
Trees can flower several times over the year, usually with two distinctive periods of heaviest flowering[]. It is an excellent pollen producing species that is important to beekeepers[].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].

Edible Uses

Flowers - cooked[]. Rich in pollen, they are often used in fritters[].

The bark exudes an edible gum[]. Some species produce a gum that is dark and is liable to be astringent and distasteful, but others produce a light gum and this is sweet and pleasant. It can be sucked like candy or soaked in water to make a jelly[]. The gum can be warmed when it becomes soft and chewable[].

Seed - cooked. It is dried, ground into a flour and used with cereals in making cakes etc[, , , ]. The flavour is somewhat like peanut butter[]. The pods are up to 10cm long, containing seeds up to 6mm long[]. Acacia seeds are highly nutritious and contain approx 26% protein, 26% available carbohydrate, 32% fibre and 9% fat[]. The fat content is higher than most legumes with the aril providing the bulk of fatty acids present[]. These fatty acids are largely unsaturated which is a distinct health advantage although it presents storage problems as such fats readily oxidise[]. The mean total carbohydrate content of 55.8 + 13.7% is lower than that of lentils, but higher than that of soybeans while the mean fibre content of 32.3 + 14.3% is higher than that of other legumes such as lentils with a level of 11.7%[]. The energy content is high in all species tested, averaging 1480+270 kJ per 100g[]. Wattle seeds are low glycaemic index foods. The starch is digested and absorbed very slowly, producing a small, but sustained rise in blood glucose and so delaying the onset of exhaustion in prolonged exercise[].

The ground seed can be used to produce a high quality, caffeine-free coffee-like beverage[].

A sweet red or white 'lerp' that forms on the leaves and branches is eaten[]. Lerp is a protective shield secreted from the anus of sap-sucking insects[]. The taste is sweet and it was used as a staple food by the Aborigines in some areas of Australia[]. It is not clear if the lerp is eaten when the insects are still present or if it can be eaten after they have gone[].

A large succulent gall, known as 'mulga apple' is produced by the tree and is said to quench the thirst[, ].

Medicinal

The plant (part not specified) has been used for its healing properties for treating colds and flu-like illness and in postnatal care[].

The bark of all Acacia species contains greater or lesser quantities of tannins and are astringent. Astringents are often used medicinally - taken internally, for example. they are used in the treatment of diarrhoea and dysentery, and can also be helpful in cases of internal bleeding. Applied externally, often as a wash, they are used to treat wounds and other skin problems, haemorrhoids, perspiring feet, some eye problems, as a mouth wash etc[, ].
Many Acacia trees also yield greater or lesser quantities of a gum from the trunk and stems. This is sometimes taken internally in the treatment of diarrhoea and haemorrhoids[].

Agroforestry Uses:

The nitrogen-fixing capacity, tolerance to drought and extensive root system of this plant makes it suitable for erosion control and soil improvement[, ].
In arid areas the species is used to provide shelter and shade[].

Other Uses

A yellow dye is obtained from the flowers[].
A green dye is obtained from the seed pods[].

The twigs are used to make a dish mop[].

The resinous phyllodes are used as an adhesive resin[].

The bark is a source of tannins. Yields can range from 10 - 20%[]. Bark harvested for its tannins should only be taken from mature stems, and only when the sap is rising at the beginning of the growing season – which is when the tannin content is highest and the bark is most easily removed from the wood[].

The heartwood is dark brown with contrasting markings of golden yellow; it is clearly demarcated from the white sapwood. The wood is close-grained, very hard; durable in the ground. It turns well and takes a high polish. Traditionally used for making weapons and tools, it is a useful, decorative wood, but unfortunately its log size, which rarely exceeds 5 x 25 cm, restricts its use to small turnery items, inlay etc[, , ]. It is used extensively for ornaments and fencing posts[, , , , ].
The wood makes an excellent firewood and charcoal[, ].

Propagation

Seed - best sown as soon as it is ripe in a sunny position in a nursery seedbed[]. Like many species within the family Fabaceae, once they have been dried for storage the seeds of this species benefits from scarification before sowing in order to speed up and improve germination. This can usually be done by pouring a small amount of nearly boiling water on the seeds (being careful not to cook them!) and then soaking them for 12 - 24 hours in warm water. By this time they should have imbibed moisture and swollen - if they have not, then carefully make a nick in the seedcoat (being careful not to damage the embryo) and soak for a further 12 hours before sowing[]. Treated seed germinates in 3 - 4 weeks at 25°c[]. As soon as the seedlings are large enough to handle, prick them out into individual pots and grow them on in a sunny position. Nursery growth is slow with seedlings often taking 6 - 8 months to reach 20cm tall[].
Dormancy is evident in fresh seed but disappears after 1 year. Viability is maintained for 13 years with air-dried seeds stored at room temperature and increases with seed age up to 3 years. Even when 20 years old, a germination rate of 13% has been achieved[].
Cuttings of half-ripe wood with a heel, planted in individual pots[]. Fair percentage[].

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