Acacia longifolia is a bushy shrub or small tree, which may form thickets. It grows up to 7-8 m tall. Phyllodes are typically thin and pliable and range from 5 to 20 cm long and 5 – 15 mm wide. Usually broadest near the middle or just below, and gradually narrows towards the apex. Pods are generally straight or (very) slightly curved. Twigs are sharply angled and either sparsely hairy or smooth. Inflorescence consists of a spike of pale- to golden-yellow flowers.\r\n

The related acacia species A. sophorae is often mistaken for A. longifolia, as they appear similar. However, there are a few major differences between them. Acacia sophorae typically has coiled or contorted pods, while the phyllodes are usually thick and often fleshy. The widest point of the phyllodes also differs - A. sophorae phyllodes are usually broadest near or above the middle. (Hill 2005, NZPCN 2010).

Acacia longifolia used to be classified as part of the pea family (Fabaceae), subfamily Mimosoideae, but is now classified as part of Mimosaceae (Hill, 2005).

Acacia longifolia propagates from seed. It reaches sexual maturity in two to three years. Flowering occurs in July to August in its native range and in New Zealand (NZPCN, 2010). In Portugal most trees flower during February to March; pods are formed between March and July and buds between July and March (Morais & Freitas 2008).

Acacia longifolia is primarily introduced as an ornamental, and to stabilise sand dunes in coastal areas.

Acacia longifolia flourishes in coastal areas, particularly those that were disturbed by fire. It is also found in riparian zones, scrub area, grassland and woodland. Acacia longifolia grows in a variety of habitats, including nutrient-poor ecosystems - this is thought to be due, in part, to its ability to fix nitrogen (Werner et al. 2009). While tolerant to dry periods, frost and sea spray, a major limiting factor is thought to be rainfall as A. longifolia generally propagates in areas that receive at least 550 mm rainfall annually (Department of Primary Industries 2009a). Disturbance by fire may cause mass germination.

Acacia longifolia produces large quantities of seeds annually (up to 11,500 per tree), which are thought to be viable for 50 years. In Portugal often more than 90% of the seeds are viable (E. Marchante, pers. comm.).

Introduced to dune-based coastlands for dune management.Acacia longifolia is sold for ornamental purposes. Seeds for sale online, for eg in New Zealand on the TradeMe website (http://www.trademe.co.nz).

Impacts include reduction in native biodiversity, ecosystem change, habitat alteration and changes in hydrology and fire regimes (le Maitre et al. 2002; van Wilgen et al. 2004, Marchante et al. 2003). Many of the impacts are due to changes in habitat and ecosystem that A. longifolia causes. Examples include modification of soil microbiota and soil chemistry, and modification of shade in riparian habitats (Marchante et al. 2009; Samways & Taylor 2004). Acacia longifolia may also provide stabilisation to sediment in areas which are traditionally free-flowing, modifying riparian zones and coastal sediment flow (Galatowitsch & Richardson 2005). In terms of changes in fire regimes, the presence of A. longifolia (especially thickets) increases the risk and intensity of fires. However, due to the nature of A. longifolia seed and high growth rate, A. longifolia also hinders regeneration of native flora after fire. Some of these impacts can be long-lasting, even after the removal of the invasive species (Marchante et al. 2004, Marchante et al. 2009).

A variety of management techniques have been used to manage the spread of A. longifolia, including biological control, and physical methods.\r\n

Biological: Biological control agents used are the gall wasp, Trichilogaster acaciaelongifoliae, and the seed-feeding weevil, Melanterius ventralis (Dennill & Donnelly 1991). Both of these insects control A. longifolia at seed level - T. acaciaelongifoliae affects floral buds and occasionally vegetative buds, causing gall formation that halts normal development of buds, while M. ventralis preys on seeds that are unaffected by T. acaciaelongifoliae (Dennill & Donnelly 1991). Together these two organisms have decreased A. longifolia reproductive potential by >90% in South Africa (Dennill et al. 1999). Similar biological control agents are being investigated for New Zealand and Portugal (Hill 2005; Marchante et al. 2005).\r\n

Physical and Other: Physical management techniques used on A. longifolia include felling, felling followed by herbicide application on stumps, felling, ringbarking and prescribed burning. As resprouting can occur after felling (although not always), a combination of these techniques is sometimes used (Galatowitsch & Richardson 2005; Hicks et al. 2001; Marchante et al. 2005.)