Acacia farnesiana (L.)Willd.

Code

ACAFA

Growth form

Shrub

Biological cycle

Perennial

Habitat

Terrestrial

Global description

Acacia farnesiana is a tortuous and irregular shrub, very ramified and very spiny, 2 to 6 m tall. Branches of brownish-gray color with fine white spots. Leaves compound, 4-6 primary pinnae divided into 5-20 pairs of leaflets 0.5-1 cm long. Sharp spines (1 to 2.5 cm long), hard, implanted at the base of each leaf. Flowers grouped into pedunculate globular heads 1.5 to 2 cm in diameter, yellow to orange, very fragrant. The fruits are cylindrical pods of brown to black color at maturity 4-6 cm long.

 

Mayotte : Acacia farnesiana flowers from November to August and fruits from November to October.
New Caledonia: After a period of dormancy, germination occurs during the first heavy rains of the hot season. The slow growth at the start accelerates as soon as the root system is established. There is a slowdown in the cool and dry seasons. Flowering occurs in individuals of 3 years, it starts in the rainy season. The pods are ripe since October when the protein content of this legume (leaves and pods) makes it an interesting standing fodder or indispensable in the driest extensive areas. The plant restarts after fires emitting rejects. A. farnesiana has a lifespan of between 10 and 50 years.

 

Acacia farnesiana is a perennial species. It reproduces by seeds that are dispersed by faling down or are transported by livestock that ingest pods, by runoff of water, vehicles and agricultural machinery, or shoes.

 

Acacia farnesiana can be distinguised from Acacia nilotica by spines and pod shape.

Spines	Pod	Species
Strait, short (2 (-3) cm) and brown	Subcylindrical, 4-10 cm, dark colored	Acacia farnesiana
Strait, long (0,5 - 10 cm) and white	Tightly oblong, compressed between seeds, tomentose, and white-grey	Acacia nilotica

 

Mayotte: Acacia farnesiana is an exotic species commonly naturalized in xerophilous zones and to a lesser extent in degraded environments of mesophilous and hygrophilous zones. It is present in urban areas, along roadsides, in crops and wastelands and in the dry secondarized vegetation of the coastal zone.
New Caledonia: Acacia farnesiana is very common in the pastures of the west coast and in the clearings of degradated dry forests.
Reunion: Naturalized in the dry savannas of the west coast of the island.

 

Origin

Acacia farnesiana is native to tropical America.

Worldwide distribution

Acacia farnesiana has long been introduced and naturalized in many tropical, subtropical and Mediterranean regions, preferably in dry areas up to 1000 m altitude. Introduced in New Caledonia in 1866 as a forage plant. Introduced in the 3 islands of Mascarenes (Reunion, Mauritius and Rodrigues).

Overall harmfulness

According to SPREP, the species is one of the 33 most harmful invasive species of the Pacific Islands (including New Caledonia). It is considered a major weed in Australia, Fiji, Indonesia, Paraguay and Mexico, and as a common weed in Hawaii.

Local harmfulness

New Caledonia: Acacia farnesiana is now very common in pastures and threatening for dry cleared forests. Its thorny nature, however, reduces its interest and makes it an invasive species when it densifies to completely close certain pastures making the handling of livestock on horseback or with vehicles very difficult.
Reunion: This species is not considered a crop weed but can form dense and impenetrable stands in the dry savannah areas of the island.

 

Local control

New Caledonia: To avoid stand expansion, livestock from areas with mature Acacia farnesiana pods should not be moved to areas of low concern. Given the foraging role of A. farnesiana, it is necessary to limit the development of the species by a regular rotary crushing instead of eradicating it. The low-level rotary crushing before the plant is fruiting can limit the expansion, dispersion and densification of stands considered sufficiently abundant. In invasion situations, mechanical control must be combined with chemical spray treatment on young shrubs with triclopyr as the active ingredient. On older individuals, it is necessary to make a brush application on freshly cut stump flush (picloram + 2,4-D).

Herbarium pictures ReCOLNAT: https://explore.recolnat.org/search/botanique/simplequery=Acacia%2520farnesiana