Appearance

Acacia melanoxylon is a straight trunked, medium sized tree of the legume family (Fabaceae) with a dense crown. It is a thornless, evergreen tree 26-49 ft. (8-15 m) high. It can occasionally get up to 148 ft. (45 m) tall. Native of rainforest areas in southeastern Australia, it was introduced as a forestry planting to Hawaii, New Zealand, and South Africa. It was introduced to Hawaii as a forestry planting (Nelson and Schubert 1976). 

Foliage

The leaves are bipinnate on seedlings. In mature trees coppice shoots usually become phyllodes. Phyllodes on Acacia melanoxylon are about 3-4 in. (7-10 cm) long. Foliage starts out greyish turning dark dull-green as it matures. The leaves are straight to slightly curved, with 3-7 prominent longitudinal veins and fine net-veins between. 

Flowers

The pale yellow to whitish colored flowers have a powder puff appearance due to the presence of numerous stamens. Each one ranges from 0.2-0.4 in. (5-10 mm) in diameter. The flower clusters are borne on peduncles from 0.2-0.6 in. (5-14 mm) long. They are alternately arranged and arise from the phyllode axil. Flowering can occur year round. 

Fruit

The fruit of Acacia melanoxylon is an elongated, flattened pod approximately 1.6-6 in. (4-15 cm) long and 0.1-0.3 in. (3.5-8 mm) wide. The pods are strongly curved, twisted or coiled. These pods are mostly glabrous with only a slight constriction between each seed. The pods are green and leathery when young, maturing to brown to reddish-brown in color and become woodier. The seeds are elliptic and about 0.1-0.2 in. (3-5 mm) long and 0.07-0.1 in. (1.7-3 mm) wide. Seeds are glossy, black and are encircled by a large pink to dark red aril. 

Ecological Threat

Acacia melanoxylon is native to eastern Australia. This tree grows fast and tall, up to 148 ft. (45 m) tall. It tolerates a wide range of conditions and soils but grows better in colder climates. It invades areas such as natural vegetation, commercial timber plantations and farmland. 

Selected Images

Maps

Invasive Listing Sources

• California Invasive Plant Council
• Jil M. Swearingen, Survey of invasive plants occurring on National Park Service lands, 2000-2007
• John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995.
• Reichard, Sarah. 1994.  Assessing the potential of invasiveness in woody plants introduced in North America. University of Washington Ph.D. dissertation.
• WeedUS - Database of Plants Invading Natural Areas in the United States

References