Acacia auriculiformis

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 by 5 m at a fast rate.
It is hardy to 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 , medium and heavy soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: 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.

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 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.