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17 March 2011

Acacia




Spring is here.  The Acacias are now flowering in Tunis and it is such a beautiful sight.  

"Acacia is a genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae, first described in Africa by the Swedish botanist Carl Linnaeus in 1773. Many non-Australian species tend to be thorny, whereas the majority of Australian acacias are not. They are pod-bearing, with sap and leaves typically bearing large amounts of tannins and condensed tannins that historically in many species found use as pharmaceuticals and preservatives.

 
The generic name derives from ακακία (akakia), the name given by early Greek botanist-physician Pedanius Dioscorides (ca. 40-90) to the medicinal tree A. nilotica in his book Materia Medica.  This name derives from the Greek word for its characteristic thorns, ακις (akis, thorn).  The species name nilotica was given by Linnaeus from this tree's best-known range along the Nile river.

Acacias are also known as thorntrees, whistling thorns or wattles, including the yellow-fever acacia and umbrella acacias.

Until 2005, there were thought to be roughly 1300 species of acacia worldwide, about 960 of them native to Australia, with the remainder spread around the tropical to warm-temperate regions of both hemispheres, including Europe, Africa, southern Asia, and the Americas. However, the genus was then divided into five, with the name Acacia retained for the Australian species (and a few in tropical Asia, Madagascar and Pacific Islands), and most of the species outside Australia divided into Vachellia and Senegalia. The two final genera, Acaciella and Mariosousa, only contain about a dozen species from the Americas each.

Food uses
Acacia seeds are often used for food and a variety of other products.

In Burma, Laos and Thailand, the feathery shoots of Acacia pennata (common name cha-om, ชะอม and su pout ywet in Burmese) are used in soups, curries, omelettes, and stir-fries.

Honey made by bees using the acacia flower as forage is considered a delicacy, appreciated for its mild flowery taste, soft running texture and glass-like appearance. Acacia honey is one of the few honeys which does not crystallize.

In Mexico the seeds are known as Guajes. Guajes or huajes are the flat, green pods of an acacia tree. The pods are sometimes light green or deep red in color—both taste the same. Guaje seeds are about the size of a small lima bean and are eaten raw with guacamole, sometimes cooked and made into a sauce. They can also be made into fritters. The ground seeds are used to impart a slightly garlicy flavor to a mole called guaxmole (huaxmole). The dried seeds may be toasted and salted and eaten as a snack referred to as "cacalas". Purchase whole long pods fresh or dried at Mexican specialty markets.



The first-known predominantly vegetarian spider Bagheera kiplingi, which is found in Central America and Mexico, was first documented and filmed in 2009 feeding from the tips of the acacia plants which are known as Beltian bodies which contain high concentrations of protein. All other 40,000 known species of spider's diets are mainly believed to be carnivorous.


Gum
Various species of acacia yield gum. True gum arabic is the product of Acacia senegal, abundant in dry tropical West Africa from Senegal to northern Nigeria.


Acacia arabica is the gum-Arabic tree of India, but yields a gum inferior to the true gum-Arabic.

Medicinal uses
Many Acacia species have important uses in traditional medicine. Most of the uses have been shown to have a scientific basis since chemical compounds found in the various species have medicinal effects.


In Ayurvedic medicine, Acacia nilotica is considered a remedy that is helpful for treating premature ejaculation. A 19th century Ethiopian medical text describes a potion made from an Ethiopian species of Acacia (known as grar) mixed with the root of the tacha, then boiled, as a cure for rabies.


An astringent medicine high in tannins, called catechu or cutch, is procured from several species, but more especially from Acacia catechu, by boiling down the wood and evaporating the solution so as to get an extract.

Land Reclamation
Acacia can be planted for erosion control, especially after mining or construction damage.

Ecological invasion
For the same reasons it is favored as an erosion-control plant, with its easy spreading and resilience, some varieties of acacia, namely Acacia mearnsii, are potentially an invasive species. Introduced worldwide it has become an invasive plant which is taking over grasslands and the abandoned agricultural areas, especially in moderate coastal and island regions where mild climate propagates its spreading. Australian/New Zealand Weed Risk Assessment gives it a "high risk, score of 15" rating and it is considered one of the world's 100 most invasive species.  Extensive ecological studies should be performed before further introduction of acacia varieties as this fast-growing plant, once introduced, spreads fast and is extremely difficult to eradicate."
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