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: Ear-Pod Wattle

General Information

Ear-pod wattle is a very fast-growing evergreen tree with dense foliage and an open, spreading crown[]. It grows 15 - 30 metres tall with a crooked bole that is up to 12 metres long and 50cm in diameter[]. Although it produces leaves as a seedling, llike most members of the genus the mature plant does not have true leaves but has leaf-like flattened stems called phyllodes[].
The wood is a very good fuel and is widely utilized for that purpose[], the plant is also harvested from the wild for local use as a medicine. The tree is commonly planted in tropical Asia, particularly as a fuel crop and to provide pulp for the paper industry; and is also sometimes planted in S. America and Africa[, ]. An excellent shade tree, it is planted to provide shelter on beaches and beachfronts[].
The population is currently believed to be stable and no major threats are known at present. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

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 - Queensland, north through Papua New Guinea to Indonesia.

Habitat

A riparian species, ringing perennial rivers and semi-perennial creeks, and tending to form discontinuous populations along drainage systems[]. Savannahs, woodlands, swamp edges, coastal savannas, grasslands, monsoon forests and regrowth[].

Properties

Weed Potential	Yes
Conservation Status	Least Concern
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	25.00 m
Growth Rate	Fast
Pollinators	Insects
Cultivation Status	Cultivated, Wild

Cultivation Details

The tree is predominantly found at low elevations in the seasonally dry tropical lowlands of the humid and sub-humid zones[]. It is usually found at elevations below 80 metres, but can be found up to 400 metres[]. In its natural range, the mean annual rainfall varies from 700 - 2,000 mm, and the dry season (i.e. Monthly rainfall less than 40 mm) can be up to 7 months[]. The mean maximum temperature of the hottest month is 32 - 34°c, and the mean minimum of the coolest month is 17 - 22°c[]. Frost does not occur in its natural range, but elsewhere, it tolerates light frost[].
Requires a sunny position, it is very intolerant of shade[, ]. Found most commonly on clay soils, it exhibits the ability to grow in a wide variety of soils including calcareous sands and black cracking clays, poor-fertility soils, seasonally waterlogged soils, sandy loams and coral rag[, ]. It can also tolerate highly alkaline and saline soils, pH ranging between 4.3 and 9[, ]. It has brittle, easily-broken branches and therefore requires a position sheltered from strong winds[]. Established plants can tolerate periodic inundation and are also very drought tolerant[].
Often cultivated for timber outside its native range, the tree has escaped from cultivation in many parts of the tropics and has become an invasive weed in some areas[, ].
Very fast-growing, an increment in height of 2 - 4 metres per year in the first few years is common even on soils of low fertility[].
The optimal planting density is not clearly established. Most current plantings are spaced at 2 - 4 x 2 - 4 metres, the closer spacing being more suitable for firewood and pulp plantations[].
The tree responds well to pollarding[].
Young trees respond to coppicing better than old trees, but the tree does not sprout vigorously or prolifically. Best results are obtained if the stump is cut at a height of 0.6 - 1 metre above the ground[]. Under favourable conditions, trees may reach a height of 15 metres in 5 years and produce an annual wood increment of 15-20 cubic m/ha over 10 - 12 years[].
Recommended rotation is 4 - 5 years for fuel wood, 8 - 10 years for pulp and 12 - 15 years for timber[].
Removal of lower branches and of young plants has been suggested as a means of improving stem form and of reducing the incidence of multiple stems[].
The tree has a shallow, spreading root system[].
Seedlings have the ability to compete with Imperata cylindrica during early growth phases and once mature may reduce the grass to a sparse ground cover[].
Hybridizes with A. Mangium[].
The plant flowers and produces fruit throughout much of the year[].
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

None known

Medicinal

A decoction of the root is used to treat aches and pains and sore eyes[].

An infusion of the bark has been used to treat rheumatism[].

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:

In its native habitat, the tree is a colonizer of tropical coastal lowlands. It has the potential to be a pioneer species, but its tendency to spread into the local environment reduces its value as a pioneer outside of its native range[, ].
The plant has a spreading, superficial and densely matted root system, which makes it suitable for stabilizing eroded land[]. Its rapid early growth, even on infertile sites, ability to fix atmospheric nitrogen and tolerance of both highly acidic and alkaline soils make it popular for stabilizing and revegetating mine spoils[].
Plantations of the tree improve soil physio-chemical properties such as water-holding capacity, organic carbon, nitrogen and potassium through litter fall. Its phyllodes provide a good, long-lasting mulch[].
The dense, dark-green foliage, which remains throughout the dry season, makes it an excellent shade tree[].

Other Uses

The bark contains sufficient tannin (13 - 25%) for commercial exploitation[]. 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[].

A natural dye, used in the batik textile industry in Indonesia, is also extracted from the bark[].

The heartwood is light brown to dark red; it is demarcated from the yellow sapwood. The wood is hard, has a high basic density; is fine and straight-grained; often attractively figured; reasonably durable and finishes well[, ]. It is excellent for turnery articles, toys, carom coins, chessmen and handicrafts[]. Also used for furniture, joinery, tool handles, and for construction if trees of suitable girth are available[].
The wood is extensively used for paper pulp. Plantation-grown trees have been found promising for the production of unbleached kraft pulp and high-quality, neutral, sulphite semi-chemical pulp[].
A major source of firewood, its dense wood and high energy (calorific value of 4500-4900 kcal/kg) contribute to its popularity. It provides very good charcoal that glows well with little smoke and does not spark[].

Propagation

Seed - requires pre-treatment to break down the hard coat[]. Pouring a small amount of boiling water over the seeds (which cools down quickly and so does not cook the seed), and then leaving to soak for 12 hours is usually effective, as is making a small incision in the coat to allow water to penetrate. Germination levels of 40 - 80% take place in 6 - 15 days[]. Treated seeds are sown in germination beds, and seedlings are transplanted into polythene bags when they reach the 2-leaf-pair stage. Seeds can also be sown straight into polythene bags. Young seedlings should initially be kept at 50% sunlight, but this can be increased to 70% once they have been established. In general, 3 - 4 months are needed to raise seedlings to a plantable size, 25 cm in height[].
Seeds stored in airtight containers at room temperature retain their viability for several years[].
Cuttings.
Air layering.

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