Download Acacia melanoxylon (Australian blackwood)

Acacia melanoxylon (Australian blackwood)
Evergreen tree, with leaves slightly shaped like a scythe and pale yellow spherical flower heads.
Scientific name: Acacia melanoxylon R.Br.
Common names: Australian blackwood, blackwood, acacia blackwood
Family: Fabaceae (Leguminosae)
Status in Portugal: invasive species (listed in the annex I of Decreto-Lei n° 565/99, 21 December)
Risk Assessmemt score: (in development)
Synonymy: Acacia arcuata Spreng., A. melanoxylon var. arcuata (Spreng.) Ser., A. melanoxylon var.
obtusifolia Ser., Mimosa melanoxylon (R.Br.) Poir., Mimosa melanoxylon Poir., Racosperma melanoxylon
(B.Br.) C.Mart., Racosperma melanoxylon (R.Br.) Pedley
Last update: 30/06/2014
How to recognise it
Tree up to 15 m, with a dark brown rhytidome deeply
fissured.
Leaves: perennial, where the young leaves are of two
types: the first are bipinnate and the others are reduced
to phyllodes; the adult leaves are all reduced to laminar
phyllodes, slightly falcate and with 3-5 longitudinal veins.
Flowers: pale yellow, arranged in globular flower heads
of 10-12 mm diameter.
Fruits: brownish-red pods, compressed, contorted; seeds
completely encircled by an orange funicle.
Flowering: February to June.
Page 1/4
Young branch showing bipinnate leaves and falcate phyllodes with many veins.
www.invasoras.pt
Acacia melanoxylon (Australian blackwood)
Similar species
Acacia cyclops (coastal wattle) is similar but it only reaches 4 m height, it has flower heads with bright
yellow flowers and the seeds are encircled by a scarlet funicle. Acacia longifolia (Sydney golden wattle)
has some similarity, but it has linear phyllodes and the flowers are arranged in bright yellow spikes.
Characteristics that aid invasion
It reproduces by seed; it produces many seeds that remain viable in the ground for more than 50 years.
The seeds are dispersed by birds, wind, water or rodents. The seeds germinate after a space opening
and/or fire occurrences.
The species also propagates vegetatively, forming vigorous sprouts from the stump and the roots.
ORIGIN AND DISTRIBUTION
Native distribution area
Southeast Australia and Tasmania.
Distribution in Portugal
Mainland Portugal (all provinces), Azores archipelago
(islands of São Miguel, Santa Maria, Terceira,
Graciosa, S. Jorge, Pico, Faial and Flores), Madeira
archipelago (islands of Madeira and Porto Santo).
Other species where the species is invasive
Europe (Spain, France, Italy, United Kingdom), South
Africa, Asia (India), USA (California, Hawaii), South
America (Argentina, Chile), New Zealand.
Introduction reasons
For ornamental purposes. It has also been cultivated as a shade tree, for wood production and soil
improvement.
Preferential invasion environments
Roadsides and watercourses banks, skirts or understory’s of forest areas or open spaces.
It prefers granite terrains, avoiding calcareous ones. It tolerates drought, salt winds, polluted locations
and extreme temperatures very well.
IMPACTS
Impacts on ecosystems
It forms very dense populations inhibiting the development of native vegetation.
It produces a lot of nitrogen-rich litter, which promotes soil change.
Economic impacts
Expensive control methodologies.
Page 2/4
www.invasoras.pt
Acacia melanoxylon (Australian blackwood)
Natura 2000 network habitats more subject to impacts

Alluvial forests with Alnus glutinosa (Alno-Padion, Alnion incanae, Salicion albae) (91E0);

Riparian mixed forests of Quercus robur, Ulmus minor and Fraxinus angustifolia along the great rivers
(91F0);

Salix alba and Populus alba galleries (92A0);

Riparian formations on intermittent Mediterranean water courses with Rhododendron ponticum, Salix
and others (92B0);

Southern riparian galleries and thickets (Nerio-Tamaricetea and Securinegion tinctoriae) (92D0 pt1,
pt2);

Rivers with muddy banks with Chenopodion rubri p. p. and Bidention p. p. vegetation (3270);

Arborescent matorral with Laurus nobilis (5230);

Thermo-Mediterranean and pre-desert scrub (5330).
CONTROL
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 melanoxylon 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 with brushcutter: preferential methodology for plants resulting from the germination that are
still very small. It should just be applied on warm days as long as the security conditions are respected.
Ring-barking: preferential methodology for adult plants with a smooth, unwounded bark. Make a
continuous ring incision around the trunk, at the height most comfortable for the operator, and remove
all the bark and vascular cambium until the ground surface, if possible, until the root. It should be applied
only when the vascular cambium is active, which may vary from place to place; the best seasons for this
technique coincide with warm temperatures and some humidity. Ring-barking for this species becomes
more difficult in large individuals that have very thick bark; in these situations, one may use a chainsaw to
perform the incisions/cuts.
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 stump
surface. If shoots should latter on appear, these should be immediately eliminated through cutting,
pulling or foliar application of herbicide (active substance: glyphosate); up to 25 to 50 cm high. Shoots of
larger dimensions (from 2-3 cm diameter) may be peeled off or else should be repeated the initial
methodology (cut stump method) .
Page 3/4
www.invasoras.pt
Acacia melanoxylon (Australian blackwood)
Chemical control
Foliar application of herbicide: over recent sprouts (25-50 cm tall) or when high germination rates occur.
Spray with herbicide (active substance: glyphosate) limiting as much as possible its application to the
target species. Due to the existence of phyllodes with thick cuticles, this method may prove to be
inefficient; in some situations, the application of herbicide with an atomizer improves the results.
Biological control
The weevil Melanterius acaciae Lea (Coleoptera: Curculionidae), that feeds off the A. melanoxylon seeds
(and sporadically of nearby A. cyclops and A. saligna), was introduced in South Africa in 1986, currently
verifying extensive damage in the target species.
This agent has not yet been tested in Portugal as to verify its safety relatively to native species, so its use
has not yet constituted an alternative in our country.
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.
For additional information, visit the webpage www.invasoras.pt and/or contact us at [email protected].
REFERENCES
Agricultural Research Council - Plant Protection Research Institute - Weed Research Division (2014) Management of invasive
alien plants: A list of biocontrol agents released against invasive alien plants in South Africa. Available: http://
www.arc.agric.za/arc-ppri/Documents/WebAgentsreleased.pdf [Retrieved 03/03/2014].
Campbell P (1993) Wattle Control. Plant Protection Research Institute. Handbook n° 3. Pretoria, South Africa, 43pp.
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 n o 1: 45-54.
Fernandes FM, Silva L, Land EO (2008) Acacia melanoxylon R. Br. In: Silva L, Land EO, Luengo JLR (eds) Flora e fauna terrestre
invasora na Macaronésia. Top 100 nos Açores, Madeira e Canárias. Arena, Ponta Delgada, pp. 342-345.
Global Invasive Species Database (2012) Acacia melanoxylon. Available: http://www.issg.org/database/species/ecology.asp?
si=197&fr=1&sts=sss&lang=EN [Retrieved 06/11/2012].
Marchante E, Freitas H, Marchante H (2008) Guia prático para a identificação de plantas invasoras de Portugal Continental.
Imprensa da Universidade de Coimbra, Coimbra, 183pp.
Page 4/4
www.invasoras.pt