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Acacia longifolia

Evergreen shrub or small tree, with bright yellow spikes; very frequent in coastal dunes.

Scientific name: Acacia longifolia (Andrews) Willd.

Common names: Sydney golden wattle, golden wattle

Family: Fabaceae (Leguminosae)

Status in Portugal: invasive species (listed in the Decreto-Lei nº 92/2019, 10 july)

Risk Assessment score: 30| Value obtained according to a protocol adapted from the Australian Weed Risk Assessment (Pheloung et al. 1999), by Morais et al. (2017), according to which values above 13 mean that the species has risk of having invasive behavior in the Portuguese territory | Updated on 30/09/2017.

Synonymy: Acacia longifolia (Andrews) Willd. var. typica Benth., Mimosa longifolia Andrews, Mimosa macrostachya Poiret, Phyllodoce longifolia (Andrews) Link Racosperma longifolium (Andrews) Martius

Last update: 30/06/2021

Family: 
Fabaceae (Leguminosae)
Appearence: 
Trees and shrubs

How to recognise it

Shrub or small tree up to 8 m.

Leaves: evergreen, reduced to laminar phyllodes, oblong–lanceolate; with 2-4 longitudinal veins.

Flowers: bright yellow arranged in axillary spikes.

Fruits: cylindrical pods, contorted in maturation; seeds with a short, whitish funicle.

Flowering: December to April.  

Similar species

Acacia cyclops (coastal wattle) is similar but has phyllodes that are generally smaller, lighter and slightly falcate; the flowers are arranged in globular flower heads, the pod is compressed and the funicle is scarlet and completely encircles the seed. Acacia melanoxylon (Australian blackwood) also has some similarity, but the phyllodes are falcate, the flowers are arranged in globular flower heads and the seeds are completely encircled by an orange funicle.

 

Characteristics that aid invasion

It reproduces by seed, producing many seeds that remain viable in the ground for many years. Seed production may reach 12000 seeds/m2/year, where most part accumulates underneath the tree. The seeds are dispersed by animals, mainly birds and ants, which lead to the formation of invasion foci. Germination is stimulated by fire. It presents a high growth rate.

The species also propagates vegetatively, forming shoots from the stump in some situations. However, in understory areas, under some climate conditions or seasons of the year, the species sprouts much less vigorously or may even not sprout.

Native distribution area
Southeast Australia.

Distribution in Portugal

Mainland Portugal (Trás-os-Montes, Minho, Douro Litoral, Beira Litoral, Estremadura, Ribatejo, Alto Alentejo, Baixo Alentejo, Algarve), Madeira archipelago (islands of Madeira and Porto Santo).

 

 

Geographic areas where there are records of Acacia longifolia

Other places where the species is invasive

Europe (France, Spain, Italy), South Africa, New Zealand, South America (Brazil), Western USA (California), Asia (Israel).

 

Introduction reasons

For ornamental purposes and for erosion control, mainly in costal dunes.

 

Preferential invasion environments

Coastal dunes and watercourses. It also appears, although less frequently, along roadsides and over interior mountainous areas.

It is one of the invasive species that causes stronger impacts on dune ecosystems.

Impacts on ecossystems

It forms very dense populations inhibiting the development of native vegetation, diminishing the flow of watercourses.

It produces a lot of nitrogen-rich litter, which promotes change in soil composition (carbon and nutrients, mainly nitrogen) and microbiology.

 

Economic impacts

Expensive control methods.  

 

Natura 2000 Network habitats more subject to impacts

– Southern riparian galleries and thickets (Nerio-Tamaricetea and Securinegion tinctoriae)  (92D0 pt1, pt2);

– Vegetated sea cliffs of the Atlantic and Baltic coasts (1230);

– Shifting dunes along the shoreline with Ammophila arenaria («white dunes») (2120);

– Fixed coastal dunes with herbaceous vegetation («grey dunes») (2130);

– Atlantic decalcified fixed dunes (Calluno-Ulicetea) (2150);

– Dunes with Salix repens ssp. argentea (Salicion arenariae) (2170);

– Wooded dunes of the Atlantic, Continental and Boreal region (2180);

– Humid dune slacks (2190); – Malcolmietalia dune grasslands (2230);

– Coastal dunes with Juniperus spp. (2250);

– Cisto-Lavenduletalia dune sclerophyllous scrubs (2260);

– Wooded dunes with Pinus pinea and/or Pinus pinaster (2270);

– Inland dunes with open Corynephourus and Agrostis grasslands (2330);

– Rivers with muddy banks with Chenopodium rubri p. p. and Bidention p. p. vegetation (3270).

Controlling an invasive species demands a well-planned management, which includes the determination of the invaded area, identifying the causes of invasion, assessing the impacts, defining the intervention priorities, selecting the adequate control methodologies and their application. Afterwards it is fundamental to monitor the efficiency of the methodologies and recuperation of the intervened area as to perform, whenever necessary, the follow-up control.

The control methodologies used for Acacia longifolia include:

Physical control

Hand pulling: preferential methodology for seedlings and small plants. When in more compacted substrates, hand pulling must be made during the rainy season as to facilitate the removal of the root system. It should be guaranteed that no stumps and main roots are left in the ground.

Cutting: preferential methodology for adult plants. Care should be taken to cut the trunk as close to the ground as possible by using manual and/or mechanical equipment. It should be done before seed maturation. Most times, this operation is enough for the effective control of the species. However, there are situations where the sprouting occurs after cutting, making necessary the application of this methodology in posterior interventions in combination with other methodologies, namely the application of herbicide.

 

Physical + chemical control

Cut stump method: Apply to adult plants. Cut the trunk as close to the ground as possible and immediately (in the following seconds) apply herbicide (active substance: glyphosate) to the cut stump. If shoots should latter on appear, these should be immediately eliminated when they reach 25 to 50 cm height by cutting or pulling.

 

Biological control

The wasp Trichilogaster acaciaelongifoliae (Hymenoptera: Pteromalidae) is used with success in South Africa since 1982. This species forms galls on the floral and vegetative buds of A. longifolia inhibiting the formation of up to 90% of the seeds. Its use is combined with the weevil [Melanterius ventralis (Coleoptera: Curculionidae)] that feeds off the few remaining seeds that are formed.

OThe specificity tests, in quarantine, to evaluate the security in using T. acaciaelongifoliae in Portugal were officially authorized and concluded in 2010. Final authorization for liberation in the natural medium is being awaited.

 

Prescribed fire

It may be strategically used to favour germination of the seed bank, e.g., after the control of adult individuals (with the adequate management of the resulting biomass) and the subsequent elimination of seedlings. This method provides an advantageous reduction of the seed bank, both by destroying part of the seeds or by stimulating the germination of the remainders.

Visit the webpage How to Control for additional and more detailed information about the correct application of these methodologies.

Agricultural Research Council – Plant Protection Research Institute – weed">Weed Research Division (2014) Management of invasive alien plants: A list of biocontrol agents released against invasive alien plants in South Africa. Disponível: http://www.arc.agric.za/arc-ppri/Documents/WebAgentsreleased.pdf [Consultado 16/10/2014].

 

 

CABI (2012) Acacia longifolia. In: invasive">Invasive species">Species Compendium. CAB International, Wallingford, UK. Disponível: http://www.cabi.org/isc/ [Consultado 06/11/2012].

 

 

 

 

Dennill GB, Donnelly D, Stewart K, Impson FAC (1999) Insect agents used for the biological control of Australian Acacia species and Paraserianthes lophanta (Willd.) Nielsen (Fabaceae) in South Africa. African Entomology: Memoir no.1: 45-54.

 

 

 

 

Marchante E, Freitas H, Marchante H (2008) Guia prático para a identificação de plantas invasoras de Portugal Continental. Imprensa da Universidade de Coimbra, 183pp.

 

 

 

 

Marchante H, Freitas H, Hoffman JH (2010) Seed ecology of an invasive alien species, Acacia longifolia (Fabaceae), in Portuguese dune ecosystems. American Journal of Botany 97 (11): 1780-1790.

 

 

 

 

Marchante H, Freitas H, Hoffman JH (2011) The potential role of seed banks in the recovery of dune ecosystems after removal of invasive plant species. Applied Vegetation Science 14: 107-119.

 

 

 

 

Marchante E, Kjøller A, Struwe S, Freitas H (2008) Short- and long-term impacts of Acacia longifolia invasions on the belowground processes of a Mediterranean coastal dune ecosystem. Applied Soil Ecology 40: 210-217.

 

 

 

Morais MC, Marchante E, Marchante H (2017) Big troubles are already here: risk assessment protocol shows high risk of many alien plants present in Portugal. Journal for Nature Conservation 35: 1–1

 

Pheloung PC, Williams PA, Halloy SR (1999) A weed risk assessment model for use as a biosecurity tool evaluating plant introductions. Journal of Environmental Management. 57: 239-251.

 

 

 

 

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