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The following article was written by Leigh Kemp. If you missed his other articles be sure to read them here.
My dad once told me a story about a tree in the Sahara that he had heard of whilst fighting in the desert during the WW2. He had heard that the tree was the only one for 250 miles in either direction. I cannot remember the circumstances around the telling of the story but it resonated deeply. The idea of a gnarled, remote tree surviving against the odds has inspired me throughout my life’s journey.
I now know that the tree my dad was telling me about is the Tree of Ténéré in Niger, the loneliest, or most isolated, tree on earth. It was the sole survivor of a group of trees that thrived in less parched times. The tree stood alone for decades. The Tree of Ténéré was an acacia – the species was either A. tortillas or A. raddiana
The loneliest tree on earth, or it was till it was knocked over!
A landmark for caravans of the Sahara, the tree finally succumbed in 1973 – knocked over by a drunk truck driver. The only tree for 400 kms and a drunkard drives into it!
During my early years I was also fascinated by images of flat topped and umbrella shaped acacias on the plains of Africa. These trees were often alone in pictures, giving the impression that the trees were dotted sparsely across the plains. Giraffe and topi antelope were sometimes added to the picture.
A Topi surveying the land from its vantage point
Acacias of Africa have now been renamed into two genus’: Vachellia and Senegallia – the genus Acacia now applies to the wattles of Australia. For the sake of the story I will continue to refer to the African trees as Acacia
Over the years I have been privileged to have travelled in many parts of Africa and seen many species of Acacias. The shapes and styles of the different species have had me intrigued for as long as I have travelled. The Acacias have provided inspiration for artists, photographers, writers, conservationists and dreamers for centuries. Arguably the most famous of these inspired artists is South African painter Jacob Hendrik Pierneef.
Pierneef’s work was inspired by the South African landscape, with the acacia’s playing a massive role in his art. His ideal was to simplify the landscape and bring harmony and order to nature. Such is his artistry that his name is used to describe one of the African styles of Bonsai by South African bonsai artist; Charles Ceronio, now deceased. This style is associated mostly with Africa acacias such as the V. tortilis or Umbrella Thorn and the V. erioloba or camel thorn.
A wise old Acacia at the foot of Mt Kilimanjaro
Both the umbrella thorn and the camel thorn can grow into the famed umbrella crown, but both can grow into untidy and scrubby bushes depending on the soil and animals that feed on them. In areas where goats are kept, the trees seldom grow into anything resembling the characteristic crown.
The umbrella thorn is the tree that provides the classic images on the Serengeti plains and as such is one of the most photographed species in Africa. An iconic image of the African safari is of a leopard lying on a branch of an umbrella acacia – or feeding on a carcass it pulled into the tree.
Seeking shade under the umbrella of an Acacia on the plains of the Serengeti.
A point of interest is that the wood of the umbrella thorn was used by the Israelites in the Old Testament in the making of tabernacle furniture, including the Ark of the Covenant.
Tanzanian Acacia in the so-called Flat Top form.
Another African style of Bonsai inspired by acacias is the Flat Top Style which is mostly based on the paperbark acacia [V. sieberana]and the flat top acacia[V. abyssinica]. Unlike the Pierneef style umbrella shaped trees with dome-type tops, the flat top trees are exactly as the name says, flat topped.
It must be stated that many species of acacias can develop either a flat top or umbrella top depending on circumstances.
During my guiding years I was often asked about acacias and why they grew as they did on the African Savannahs. After many years of research and personal observation I can offer explanations ranging from herbivore activity, soil type, climate and niche playing a role. I can safely say that all these factors play a role.
Typical forms of Acacia seen in the Eastern Cape.
I grew up in the Eastern Cape Province of South Africa, in the Kei River Valley, where the sweet thorn [Vachellia karroo] is the dominant acacia in the area. The tree grows in various sizes and shapes according to where it is in the area and what stock grazes on the farm. The acacia trees on cattle farms are larger, and more varied in shape, than the trees on goat farms. As we know goats will eat everything in their path and the trees are kept well and truly trimmed.
Acacia in both flat and umbrella forms growing in a group.
As with many acacias the sweet thorn is controlled by climate and soils. In higher rainfall areas and deeper soils the trees are taller and larger whereas in areas such as the Karoo they are generally smaller. Karoo trees are also kept trimmed by greater use by herbivores.
The largest sweet thorn acacias I have seen are in the Okavango Delta in Botswana on the larger permanent islands where the soil is fertilised by the annual floods.
Giraffe do a great job of keeping Acacia neatly trimmed.
The open savannahs are the places where we find the most dramatic flat top and umbrella shaped trees. In the Serengeti ecosystem, the vast open grassland in East Africa, you can find isolated trees, or small stands of acacias with the artistic shapes. But why is it that in this seemingly very fertile plain there are so few acacias?
Not to go into too much detail, but the Serengeti has a very shallow soil deposit which ensures the nutrients stay in the shallow layer – and the grass provides for the great herds. The reason for the shallow soils is because of the layer of lava from the ‘explosion’ of the Kilimanjaro-type volcanic mountain that stood where the Ngorongoro Crater now is.
Acacia growing in the Ngorongoro Crater with its wide canopy, perhaps to protect the shallow root system below.
The lava deposit covered a vast area, which over time was covered by dust blown earth. The grasses took root and flourished but the deep-rooted trees struggled in the shallow soils. It is said that the umbrella shapes happened so as to protect the now-shallow root system by providing shade from the heat, and as some have surmised, providing shade for the animals to shelter under and as such preventing other animals from digging up the roots.
Another explanation is that in wooded areas the trees grow upwards to seek sunlight but on the open plains there is no competition so the canopies grow outwards. Animals such as giraffe do feed on the canopies but not in great enough numbers to keep the tree trimmed.
The pods of acacia trees are used as fodder for domestic stock and are much sought after delicacies for wildlife, including antelope, baboons and monkeys.
A drowned Acacia is a popular roost for birds seeking refuge from predators
I have watched impalas waiting under camel thorn and umbrella thorn trees whilst baboons feed on the seeds in the trees. The impalas know that the baboons will drop seed pods. Elephants have a taste too for the pods, often shaking a tree to dislodge them. The leaves are also fed on by giraffe and elephants. It is not unusual to see elephants standing on their hind legs to reach up to the leaves in the crown of the tree.
A Gerenuk impressively stands on its hind legs to reach the tastiest Acacia leaves
There are many reasons given for the shapes of the acacia trees of Africa and in these reasons are disagreements. One thing is not argued, however, and that is that the Acacias of Africa are inspiring in whatever shape they may be growing in.Tall, gnarled and even seemingly deformed, these trees enhance the landscape.
About the author: Leigh Kemp grew up in nature on a remote farm in the Eastern Cape. This geared him to a life of travelling the wild places of Africa for more than 35 years as a wilderness guide, tour guide, travel writer and conservationist – learning and collecting information and images on all aspects of the African wilderness. Visit his site here, contact him directly on kempleigh06[at]gmail.com or call him on +27 79 596 6671.
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