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Thursday, 26 June 2014

Acacia karroo (Vachellia karroo)

Pronunciation : vak-ELL-ee-uh kuh-roo

This is one of South Africa's most beautiful and useful trees. It is integrally part of our country's history having been used for everything from raft-making to sewing needles and fencing for the houses of the royal Zulu women. The thorns were even used by early naturalists to pin the insects they collected! It is very widespread throughout southern Africa and there are different forms in some places, which can be confusing. Acacia karroo may be found from the Western Cape through to Zambia and Angola. In tropical Africa it is replaced by Acacia seyal. The name Acacia is derived from Greek "akis" a point or barb. Karroo is one of the old spellings of karoo which cannot be corrected because of the laws governing botanical nomenclature (giving of names).

The sweet thorn makes a beautiful garden specimen. The bright yellow flowers, which appear in spring, look very striking against the dark green foliage. The rough, dark brown bark is also most attractive. The flowers are sweetly scented and are renowned for attracting insects which are essential to any bird garden. Birds also like to make nests in thorn trees as the thorns offer them some protection from predators. Caterpillars of 10 species of butterflies are dependant on the tree for survival. These include, the club-tailed charaxes (Charaxes zoolina zoolina) and the topaz-spotted blue (Azanus jesous). In cold and dry areas like where I live, the tree is deciduous.

Vachellia 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.

Regions where the Acacia Karroo can be found - I can be found approx. where the red dot is at the bottom of Southern Africa.

This tree is especially useful as forage and fodder for domestic and wild animals. Apparently, there is no risk of poisoning from it. Goats seem to like A. karoo better than cattle. The flowers appear in early summer in a mass of yellow pompons and make a very good source of forage for honey bees; honey from it has a pleasant taste.

An edible gum seeps from cracks in the tree's bark. The gum can be used to manufacture candy and it used to have economic importance as "Cape Gum". In dry areas, the tree's presence is a sign of water, both above and underground.

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 Karroo region of western South Africa. 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.

This species of thorn grows easily from seed, which should be soaked in hot water and left overnight. You will see if this has been effective as the seed will swell up. Sow the following morning. Seedling trays with seedling mix can be used, or the seeds could be sown directly into a pot. Cover lightly with sand and do not allow to dry out. Germination usually takes 3 - 12 days. The seedling will transplant well in spite of the long tap root. Wait until they unfurl their second leaves before transplanting. This little one of mine is almost ready to go into the garden, I just have to find a LARGE empty, sunny spot for it.

Ripe pods split open to reveal the seeds. Image credit

Acacia karroo is regarded as a weed inAustralia

MIMOSACEAE (Thorn tree family)  

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

The thorns on my Acacia karroo brought to mind the thought that we could take a lesson from nature and use the ‘thorns’ to our advantage, like this tree does. These thorns provide safety from browsing animals for the tree. and they are a pretty adornment as well. By looking at the thorns in our lives as a lesson and something pretty, learning from the experience so that we can handle a similar situation better, we can also have protection against the thorny side of life.


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