Ear-Pod Wattle, Black Acacia, Earleaf, Black wattle
Acacia auriculiformis

Family: Fabaceae

What it is like

A useful agroforestry plant with minor edible uses. It can grow to 20m and has a dense round crown. A crooked, gnarly tree good for shade. A rough hard bark grayish green in colour on a 50cm diameter trunk. Sickle shaped shiny dark green leaves 10-20cm long taper to a blunt tip and are 1.5 – 3.5 cm wide. Three main veins are prominent. Flowers are dull golden/yellow rods occurring in pairs. Early spring, Late spring, Mid spring. Acacia auriculiformis has distinctive ear-like pods, woody twisted and hard. Roots are shallow and spreading. There are about 1,350 Acacia species with over 1,000 occuring in Australia. Acacia auriculiformis can become invasive in the wrong conditions. Nitrogen fixing: Acacia auriculiformis can fix nitrogen after nodulating with a range of Rhizobium and Bradyrhizobium strains. It also has associations with both ecto- and endo-mycorrhizal fungi.

Acacia auriculiformis is an evergreen Tree growing to 25 m (82ft) by 5 m (16ft) at a fast rate. See above for USDA hardiness. It is hardy to UK zone 10 and is frost tender. The flowers are pollinated by Insects. It can fix Nitrogen. It is noted for attracting wildlife. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: mildly acid and neutral soils and can grow in very acid and saline soils. It cannot grow in the shade. It prefers dry or moist soil and can tolerate drought. The plant is not wind tolerant.

Height (m): 25

Where it is found

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.

Australia - Queensland, north through Papua New Guinea to Indonesia.

Conservation Status: Least Concern.

Countries/locations it is found in

Found in: Africa, Andamans, Argentina, Asia, Australia, China, East Africa, East Timor, Fiji, India, Indochina, Indonesia, Laos, Malaysia, Mauritius, Pacific, Pakistan, Panama, Papua New Guinea, Philippines, Reunion, SE Asia, Tanzania, Thailand, Timor-Leste, USA, Vietnam.

How it is used

Food

Rating: 1

Gum, Seeds - oil. The gum is eaten in Australia.

Oil: Oil

Seed: includes nuts, cereals, peas and beans.

Medicine

Rating: 0

Other

Rating: 4

Attractive flowers or blooms. 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 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.

Oil: Vegetable oils have many uses, as lubricants, lighting, soap and paint making, waterproofing etc. This does not include the edible oils unless they are also mentioned as having other uses.

Food Forest: Plants for Edible Forest Gardens and Food Forests.

How it is grown

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, 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.

Propagating it: 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.

Best place to grow:

Habit: Tree

Hardiness: 10-12

Growth: Fast

Soil: Light (sandy), medium, heavy (clay)

Shade: No shade

Moisture: Dry, moist

Things to keep in mind

This plant can be weedy or invasive: Florida Exotic Pest Plant Council. Florida. Bahamas, Bangladesh, Singapore, Hawaii, USA.

Its other names

Local names

Also known as: Akasia kuning, Bunga siam, Earleaf wattle, Kasia, Kathin-narong, Keo bong vang, Kratin-narong, Northern Black wattle, Pohon akasia, and Unar.

Synonyms

Racosperma auriculiforme (Benth.) Pedley; Acacia auriculaeformis; Acacia moniliformis Griseb.