Acacia karroo
Encyclopedia
Acacia karroo also known as the Sweet Thorn, is a species of Acacia
Acacia
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...

, native to southern Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

 from southern Angola
Angola
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...

 east to Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...

, and south to South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

.

It is a shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...

 or small to medium-sized tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

 which grows to height of 12m. It is difficult to tell apart from Acacia nilotica subsp. adstringens
Acacia nilotica subsp. adstringens
Acacia nilotica subsp. adstringens is a perennial tree. It is not listed as being threatened. Some common names for it are Cassie, Piquants Blancs and Piquant Lulu. Its geographic distribution includes Africa, Asia, the Indian Ocean area and the Middle East.Acacia nilotica subsp...

 without examining the seed pods. It is not listed as being a threatened species
Threatened species
Threatened species are any speciesg animals, plants, fungi, etc.) which are vulnerable to endangerment in the near future.The World Conservation Union is the foremost authority on threatened species, and treats threatened species not as a single category, but as a group of three categories,...

.

Common names in various languages include Karoo Thorn, Doringboom, Soetdoring, Cape Gum, Cassie, Piquants Blancs, Cassie Piquants Blancs, Cockspur Thorn, Deo-Babool, Doorn Boom, Kaludai, Kikar, Mormati, Pahari Kikar, umuNga and Udai Vel.

Identification

It is a shrub or small to medium-sized tree which grows to height of 12m. Acacia karroo has a rounded crown, branching fairly low down on the trunk. It is variable in shape and size, reaching a maximum of about 12m where there is good water. The bark is red on young branches, darkening and becoming rough with age. Sometimes an attractive reddish colour can be seen in the deep bark fissures The leaves are finely textured and dark green. The abundant yellow flowers appear in early summer, or after good rains. The seed pods are narrow, flat and crescent shaped. They are green when young becoming brown and dry. The pods split open allowing the seeds to fall to the ground. The thorns are paired, greyish to white and are long and straight

Distribution

It is a tree of open woodland and wooded grassland. It grows to its greatest size when rainfall of 800-900mm is received but can grow and even thrive in very dry conditions such as the Karoo region of western South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

. The requirement here is for deep soils that allow its roots to spread. Everywhere in its range, however, the tree is easily recognised by its distinctive long white paired thorns and coffee coloured bark, both of which are very attractive. In the tropics it shows little variation but at the southern end of its range it becomes more variable in appearance.

Adaptations

Acacia karroo has a life span of 30-40 years and is an adaptable pioneer, able to establishing itself without shade, shelter or protection from grass fires. Once over a year old, seedlings can resprout after fire. Several fungi are associated with this tree and the crown of mature trees may be parasitized by various mistletoes, leading to the tree's decline. This tree has a long taproot which enables it to use water and nutrients from deep underground, this and its ability to fix nitrogen, lead to grasses and other plants thriving in its shade.
The tree has been noted to occur in the Torre del Mar area, near Malaga, Spain. Here it grows freely as a large shrub on waste ground. It has been used as hedging to keep out goats from vegetable plots. Flowers during July.

Uses

A. karoo is used for chemical products, forage
Fodder
Fodder or animal feed is any agricultural foodstuff used specifically to feed domesticated livestock such as cattle, goats, sheep, horses, chickens and pigs. Most animal feed is from plants but some is of animal origin...

, domestic uses, environmental management, fibre, food, drink, and wood. The tough wood is white to slightly yellowish in colour, rarely producing dark brown heartwood. It is widely cultivated in Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, the Mediterranean region, India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

 and the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

 area. The large thorns mean that the tree must be approached, and the branches handled, carefully.

Food

As is common in Acacia spp., edible gum seeps from cracks in the tree's bark, and is an important part of the bushbaby's winter diet.
The gum can be used to manufacture candy
Candy
Candy, specifically sugar candy, is a confection made from a concentrated solution of sugar in water, to which flavorings and colorants are added...

 (see Gum arabic
Gum arabic
220px|thumb|right|Acacia gumGum arabic, also known as acacia gum, chaar gund, char goond, or meska, is a natural gum made of hardened sap taken from two species of the acacia tree; Acacia senegal and Acacia seyal...

) and used to have economic importance as "Cape Gum". In dry areas, the tree's presence is a sign of water, both above and underground.

Forage and fodder

The tree is especially useful as forage and fodder
Fodder
Fodder or animal feed is any agricultural foodstuff used specifically to feed domesticated livestock such as cattle, goats, sheep, horses, chickens and pigs. Most animal feed is from plants but some is of animal origin...

 for domestic and wild animals. Apparently, there is no risk of poison
Poison
In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....

ing from it. Goats seem to like A. karoo better than cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...

. The small pom-pom shaped yellow flowers are attractive in mid-summer.
The flowers make it a very good source of forage for honey bee
Honey bee
Honey bees are a subset of bees in the genus Apis, primarily distinguished by the production and storage of honey and the construction of perennial, colonial nests out of wax. Honey bees are the only extant members of the tribe Apini, all in the genus Apis...

s; honey
Honey
Honey is a sweet food made by bees using nectar from flowers. The variety produced by honey bees is the one most commonly referred to and is the type of honey collected by beekeepers and consumed by humans...

 from it has a pleasant taste.

Wood and bark

A. karroo is an excellent source of firewood
Firewood
Firewood is any wood-like material that is gathered and used for fuel. Generally, firewood is not highly processed and is in some sort of recognizable log or branch form....

 and charcoal
Charcoal
Charcoal is the dark grey residue consisting of carbon, and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen...

. The wood is also used for fencing posts for cattle byres or kraals. The heartwood has a density of about 800 kg/m³. A tough rope
Rope
A rope is a length of fibres, twisted or braided together to improve strength for pulling and connecting. It has tensile strength but is too flexible to provide compressive strength...

can be made from the inside bark of the tree.

Traditional Medicine

The gum, bark and leaves have been used as a soothing agent and astringent for colds, conjunctivitis and hemorrhage in South Africa.

Bans

Notifiable in NSW,Australia. It is illegal to not notify the NSW government of the existence of this plant.
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