Earleaf Acacia is a woody legume native of tropical Australia and Papua New Guinea. It is highly variable in the wild, from shrubs 2 to 5 m (7 to 16 ft) tall on exposed coastal sites to large timber trees reaching heights of up to 30 m (100 ft) under favourable conditions. Grown in gardens, it is more typically a medium-sized tree 10 to 15 m (30 to 50 ft) tall.
Trees on good soil with adequate moisture develop a straight trunk with smooth, greyish bark becoming fissured with age and a large, heavily branched rounded crown.
Leaves deep green, long, sickle-shaped and densely arranged, casting a deep shade.
The flowers are bright yellow, small and held in showy finger-like clusters. Flowering appears to coincide with the start of the rainy season, which is spring to summer in most areas, including its native range.
The seedpods have an unusual, curled ear shape that has led to the tree being named 'Earleaf acacia' and 'Earpod wattle'. They mature on the tree, turning brown and then split open to release their seed, which dangle from a string-like aril attached to the inside of the seedpod.
It is cultivated for a variety of environmental services, including land rehabilitation, erosion prevention and soil improvement, on account of its nitrogen-fixing capabilities, ability to grow on a wide range of nutrient-poor soils, as well as having good tolerance to drought, flooding and salty conditions.
Earleaf Acacia produces a medium-weight wood in the 600 to 750 kgs per cubic meter (37 to 46 lbs per cubic ft) range, with low to moderate natural resistance to rot and decay, making it suitable mostly for indoor and above-ground use.
The sawn timber reveals attractively figured, light-brown to dark-red heartwood, which is used above all for making fine furniture and cabinets. Small diameter logs and branchwood pieces are cut for firewood and for making charcoal, for which the tree is widely cultivated in agroforestry systems. They are also cut for poles and posts, woodcraft, including turnery and is an excellent source of pulpwood for the manufacture of paper and paper products.
It is widely cultivated as a street tree in Southeast Asia, for its fast growth, the shade it gives and its showy flowers and foliage.
Grows naturally in sub-humid to humid tropical lowland climates, generally in areas with annual lows of 17 to 25 °C, annual highs of 27 to 35 °C, annual rainfall of 700 to 2000 mm and a dry season of 3 to 8 months. However, it grows fast and reaches its best development as a timber tree in areas with annual rainfall of 1200 to 5000 mm.
New plants are usually started from seed, which remain viable for up to two years under dry, air-tight storage. It performs well on free- to slow-draining clay, loam and sand soils of an acid to alkaline nature, generally with a pH of 4.5 to 8.5, and on sites with full to partial sun exposure. It has good tolerance of both salt and seasonal flooding and can fix nitrogen from the air, making it productive on nutrient-poor soils.
It is recorded as a weed species in some countries and is assessed to be a high weed risk species for Hawaii by the Hawaii Pacific Weed Risk Assessment (HPWRA) project. Seed-eating birds are reported as the main contributors to its spread beyond cultivation.
The branches are brittle and susceptible to wind damage, increasing the risk of them falling and causing personal injury or damage to property.
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