Everything about Acacia totally explained
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 Carolus Linnaeus in 1773.
Acacias are also known as
thorntrees or
wattles, including the
yellow-fever acacia and
umbrella acacias.
There are 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 Africa, southern
Asia, and the
Americas.
Classification
Acacia is apparently not
monophyletic. This discovery has led to the breaking up of
Acacia into five new genera as discussed in
list of Acacia species.
In common parlance the term "acacia" is occasionally misapplied to species of the genus
Robinia, which also belongs in the
pea family.
Robinia pseudoacacia, an American species locally known as
Black locust, is sometimes called "false acacia" in
cultivation in the
United Kingdom.
Geography
The southernmost species in the genus are
Acacia dealbata (Silver Wattle),
Acacia longifolia (Coast Wattle or Sydney Golden pattle),
Acacia mearnsii (Black Wattle), and
Acacia melanoxylon (Blackwood), reaching 43°30' S in
Tasmania, Australia, while
Acacia caven (
Espinillo Negro) reaches nearly as far south in northeastern
Chubut Province of
Argentina. Australian species are usually called
wattles, while African and American species tend to be known as
acacias.
Acacia albida,
Acacia tortilis and
Acacia iraqensis can be found growing wild in the
Sinai desert and the
Jordan valley. It is found in the savanna vegetation of the tropical continental climate.
Description
The leaves of acacias are compound pinnate in general. In some species, however, more especially in the Australian and
Pacific islands species, the leaflets are suppressed, and the leaf-stalks (
petioles) become vertically flattened, and serve the purpose of leaves. These are known as
phyllodes. The vertical orientation of the phyllodes protects them from intense sunlight, as with their edges towards the sky and earth they don't intercept light so fully as horizontally placed leaves. A few species (such as
Acacia glaucoptera) lack leaves or phyllodes altogether, but possess instead
cladodes, modified leaf-like
photosynthetic stems functioning as leaves.
The small
flowers have five very small petals, almost hidden by the long
stamens, and are arranged in dense globular or cylindrical clusters; they're yellow or cream-colored in most species, whitish in some, even purple (
Acacia purpureapetala) or red (
Acacia leprosa Scarlet Blaze).
The plants often bear spines, especially those species growing in arid regions. These sometimes represent branches which have become short, hard and pungent, or sometimes leaf-
stipules.
Acacia armata is the Kangaroo-thorn of Australia and
Acacia erioloba is the Camelthorn of Africa.
Symbiosis
In the
Central American Acacia sphaerocephala,
Acacia cornigera, and
Acacia collinsii (collectively known as the
bullthorn acacias), the large thorn-like stipules are hollow and afford shelter for
ants, which feed on a secretion of sap on the leaf-stalk and small,
lipid-rich food-bodies at the tips of the leaflets called Beltian bodies; in return they add protection to the plant against
herbivores. Some species of ants will also fight off competing plants around the acacia, cutting off the offending plant's leaves with their jaws and ultimately killing it, while other ant species will do nothing to benefit their host.
Pests
In Australia,
Acacia species are sometimes used as food plants by the
larvae of
hepialid moths of the
genus Aenetus including
A. ligniveren. These burrow horizontally into the trunk then vertically down. Other
Lepidoptera larvae which have been recorded feeding on
Acacia include
Brown-tail,
Endoclita malabaricus and
Turnip Moth. The leaf-mining larvae of some
bucculatricid moths also feed on
Acacia:
Bucculatrix agilis feeds exclusively on
Acacia horrida and
Bucculatrix flexuosa feeds exclusively on
Acacia nilotica.
Acacias contain a number of
organic compounds that defend them from pests and grazing animals.
Uses
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 doesn't crystalize.
Acacia is listed as an ingredient in
Fresca, a
citrus soft drink, and
Barq's root beer, as well as in
Läkerol pastille candies,
Altoids mints, and
Wrigley's Eclipse
chewing gum.
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 all 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's 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, 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.
Ornamental uses
A few species are widely grown as ornamentals in
gardens; the most popular perhaps is
Acacia dealbata (Silver Wattle), with its attractive glaucous to silvery leaves and bright yellow flowers; it's erroneously known as "mimosa" in some areas where it's cultivated, through confusion with the related genus
Mimosa.
Another ornamental acacia is
Acacia xanthophloea (Fever Tree).
Southern European florists use
Acacia baileyana,
Acacia dealbata,
Acacia pycnantha and
Acacia retinodes as cut flowers and the common name there for them is
mimosa.
Ornamental species of acacia are also used by homeowners and
landscape architects for
home security purposes. The sharp thorns of some species deter unauthorized persons from entering private properties, and may prevent break-ins if planted under windows and near drainpipes. The aesthetic characteristics of acacia plants, in conjunction with their home security qualities, makes them a considerable alternative to artificial
fences and
walls.
Paints
The ancient Egyptians used Acacia in paints.
Perfume
Acacia farnesiana is used in the
perfume industry due to its strong fragrance. The use of Acacia as a fragrance dates back centuries. In The
Bible, burning of acacia wood as a form of
incense is mentioned several times.
Symbolism and ritual
The Acacia is used as a symbol in
Freemasonry, to represent purity and endurance of the
soul, and as funerary symbolism signifying resurrection and immortality.
Several parts (mainly bark, root and resin) of Acacia are used to make
incense for rituals. Acacia is used in incense mainly in India, Nepal, Tibet and China. Smoke from Acacia bark is thought to keep
demons and
ghosts away and to put the gods in a good mood. Roots and resin from Acacia are combined with
rhododendron,
acorus,
cytisus,
salvia and some other components of incense. Both people and elephants like an alcoholic beverage made from acacia fruit.
Tannin
The bark of various Australian species, known as
wattles, is very rich in
tannin and forms an important article of export; important species include
Acacia pycnantha (Golden Wattle),
Acacia decurrens (Tan Wattle),
Acacia dealbata (Silver Wattle) and
Acacia mearnsii (Black Wattle).
*Inner bark
Black Wattle is grown in plantations in
South Africa. Most Australian acacia species introduced to South Africa have become an enormous problem, due to their naturally aggressive propagation. The pods of
Acacia nilotica (under the name of
neb-neb), and of other African species are also rich in
tannin and used by tanners.
Wood
Most acacia species are used for valuable
timber; such are
Acacia melanoxylon (Blackwood) from
Australia, which attains a great size; its wood is used for
furniture, and takes a high polish; and
Acacia omalophylla (
Myall Wood, also Australian), which yields a fragrant timber, used for ornamental purposes.
Acacia seyal is thought to be the
Shittah-tree of the
Bible, which supplied shittim-wood. According to the
Book of Exodus, this was used in the construction of the
Ark of the Covenant.
Acacia koa from the
Hawaiian Islands and
Acacia heterophylla from
Réunion island are both excellent timber trees.
Indonesia (mainly in
Sumatra) and in
Malaysia (mainly in
Sarawak) plantations of
Acacia mangium are being established to supply
pulpwood to the paper industry.
Phytochemistry of Acacia
Alkaloids
As mentioned previously, Acacias contain a number of
organic compounds that defend them from pests and grazing animals. Many of these compounds are
psychoactive in humans.
The
alkaloids found in Acacias include
dimethyltryptamine (DMT),
5-methoxy-dimethyltryptamine (5-MeO-DMT) and
N-methyltryptamine (NMT). The plant leaves, stems and/or roots are sometimes made into a brew together with some
MAOI-containing plant and consumed orally for healing, ceremonial or religious uses.
Egyptian mythology has associated the acacia tree with characteristics of the
tree of life (cf. article on the
Legend of Osiris and Isis).
Further Information
Get more info on 'Acacia'.
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