Acacia longifolia

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

Acacia longifolia is a fast-growing wattle native to southeastern Australia. It is known by many common names, including long-leaved wattle, golden wattle, coast wattle, Sydney golden wattle, and aroma doble. It is not a threatened species, but it can be invasive outside Australia—in Portugal, New Zealand, and South Africa—and in southwestern Western Australia it has naturalised and become a weed.

Description
This plant can be a shrub or a tree up to about 8 meters tall, and it can grow even faster (7–10 meters) in five to six years. It has grey bark that is smooth to finely fissured. Branchlets are glabrous and angled toward the tips. Like other Acacias, it has phyllodes (flat leaf-like structures) instead of true leaves. The phyllodes are evergreen, straight to slightly curved, 4–20 cm long and 4–30 mm wide, with many prominent veins.

Flowers and fruit
Acacia longifolia mainly flowers from June to October in its native range. The inflorescences are simple cylindrical spikes, 2–4.5 cm long, with bright to pale yellow flowers. After flowering, it forms seed pods that are 4–15 cm long and 2.5–6 mm wide. The pods are dry and can be straight or twisted between the seeds.

Taxonomy
It was first named Mimosa longifolia in 1802 and later became Acacia longifolia. It has also been placed in the names Racosperma longifolium, Mimosa macrostachya, and Phyllodoce longifolia. The name longifolia refers to its long phyllodes. There are two subspecies: A. longifolia subsp. longifolia and A. longifolia subsp. sophorae, the latter growing on Tasmanian dunes.

Where it grows
In Australia, it is found along the coast from extreme southeastern Queensland and eastern New South Wales down the coasts of Victoria and into southeastern South Australia, often on sandy dunes. It also occurs on the Eyre and Yorke Peninsulas, Kangaroo Island, and the Mount Lofty Ranges. Subspecies sophorae lives on Tasmanian coasts. It has become naturalised in southwestern Western Australia, likely from garden escape or revegetation plantings.

Uses and cultivation
Acacia longifolia is widely grown in subtropical regions. It helps prevent soil erosion and provides edible flowers, seeds, and seed pods. Flowers yield a yellow dye, and pods can be used for a green dye; wood has some uses and the bark can be used for tanning. Seeds were eaten in Tasmania. It can be propagated from scarified seeds or by boiling water treatment. It makes an attractive, hardy hedge or screen, is good for hydroseeding and stabilising banks, and tolerates drought and frost. In Southern California it is popular as a street canopy tree.

Invasiveness and management
In Portugal the species is highly invasive in sand dunes and cultivation is prohibited. In South Africa, a biological control wasp, Trichilogaster acaciaelongifoliae, has been released to limit its spread, causing heavy seed reduction and other growth impacts. In places where it is considered a weed, control methods include pulling seedlings, ringbarking, or cutting and applying glyphosate to stumps.