Friday, February 4, 2011

Acacia karroo (Sweet thorn)

Of all our indigenous thorn trees, the beautiful yet hardy Acacia karroo is probably the most widely recognized, as it occurs in almost all parts of the country. Depending on the habitat and prevailing climate, the adaptable Sweet thorn will vary in size and shape from shrub-like growth to a large tree. The common name refers to the pleasant tasting, edible gum that is secreted by wounds on the bark. Acacia karroo is an indicator of sweet veld and is highly valued as an excellent fodder tree for both stock and wildlife. This tough pioneer has a 30-40 year lifespan and is able to establish itself successfully in the most challenging conditions, making it an excellent choice for farms or smallholdings where it can be difficult to care for  less resilient trees
Botanical Name
Acacia karroo
Common Name
Sweet thorn
RSA National Tree No’
As one of our most beautiful and hardy thorn trees, the Acacia karroo makes a  striking garden specimen with the lovely rounded crown, feathery dark green foliage and the profusion of sweetly scented pompon flowers, that are literally dripping with nectar. Birds and insects flock to the tree turning the garden into a veritable birders paradise. The Sweet thorn is also a popular nesting tree for birds as the long spines protect their young from predators. Plant this striking tree on a large lawn as a decorative shade tree, or, where a windbreak is needed, Acacia karroo can be trimmed into a dense, impenetrable hedge. Avoid planting this useful tree too near buildings or paving as the roots can be invasive. 
6m – 12m
Semi deciduous
Growth Habit
Acacia karroo is widespread throughout the country and is found in a variety of habitats from low lying areas to highveld areas.
The bark of the Sweet thorn is rough and dark, almost black in colour. On young branches the bark is reddish and somewhat smoother. The long straight spines are paired and are pale grey to white in colour.
The fine, dark green leaves are bi-pinnately compound with 5-20 pairs of leaflets per pinna. Petiolar glands are usually present at the base of the pinnae pairs. The tree may lose it’s leaves in very cold regions but they will quickly reappear as the weather warms up.
In summer, the tree is covered with a profusion of bright yellow, sweetly scented, pompon flowers that are extremely decorative.
The fruit consists of sickle shaped, flat pods that are green when young and ripen to brown. They are somewhat constricted between the seeds.
The dark seeds are rounded and flattish and are distributed by birds and game that feed on the tree.
Growing regions
Being highly adaptable, Acacia karroo is widespread throughout southern Africa and occurs naturally from the Western Cape through to Angola and Zambia.
Growing conditions
This impressive tree grows best when planted in a large hole with plenty of compost in full sun. Water generously and it will grow quickly in warm parts of the country.
Best season
The lovely Sweet thorn is hardy and will survive in seemingly impossible conditions.
Propagation from seed is easy, The seed should be soaked in water for approximately 3 days, or otherwise, in hot water a few hours prior to planting in ordinary garden soil.
Growth rate
If conditions are not too harsh Acacia karroo will grow fast, up to 1m per year.
Acacia karroo has numerous uses as diverse as leather tanning, raft making and medicinal purposes.
The bark, leaves and gum are used for a range of medicinal applications such as wound poultices, cold remedies and eye treatments. The heavy heart wood is used for various household items including cooking utensils and furniture. The wood needs to be soaked in water for up to six months prior to use however, as this prevents borer infestation. Aside from using the gum to make a water based glue it was exported as ‘Cape gum” for the manufacture of confectionary.
                 A. karroo Seed Pods     A. karroo Flowers and FoA. karroo Thorns and Bark

1 comment:

  1. Thank you! Yours is the only website I found that could tell me the spread of this tree :-)