This is the Umbrella Thorn (Acacia tortilis); a flagship species of acacia tree in the African savannah. It has an easily recognisable shape when it’s a fully grown adult, in fact this is where the tree acquires its name; from its umbrella-like canopy. In Afrikaans, the tree is called the ‘Haak-en-Steek’ which means roughly ‘hook and stab’ which refers to the plant’s thorns; it has one pair of sharp points and one pair of hooks at intervals along its stems. Umbrella thorns can be identified quite easily by their conspicuous white thorns however, so can many other acacias so identifying the hooks can confirm the identification.
The umbrella thorn can be found predominantly in savannah grasslands, where it often stands proudly on its own in the veld. The ubiquitous tree can be found all over Africa (as well as in parts of the Middle East) and can be found in more arid regions. In fact, the most isolated tree ever recorded stood in the Sahara desert and was most probably an umbrella thorn.
The sweet leaves of the umbrella thorn are a preferred food of many herbivores, including the towering giraffe, however, even the giraffe cannot stretch its neck far enough to penetrate the wide disc canopy and so feeds upon the leaves at the edges. Poor tree you may think; its leaves ruthlessly torn away. However, the tree has sacrificed its outer leaves but has safely protected its inner leaves. When the tree is young, it appears more bush-like and rounded, and can be confused with a myriad of other similar plants. The same is true when the tree grows in more arid areas and lacks the nutrients to grow to its full, iconic shape.
The animals that feed a lot on the umbrella thorn often have a distinctive face. Many browsing animals will have long faces; with their eyes quite far away from their mouths. Animals and plants have been evolving alongside each other in Africa for millions of years and as good as the plants are at defending themselves, the animals are good at responding to the plants’ defences. Let’s take the giraffe (Giraffa camelopardalis), a browser that enjoys the leaves of the umbrella thorn. The giraffe’s distinctive long face keeps its eyes well away from its mouth; this allows the animal to feed on a thorny plant without risking thorns or spines injuring its eyes.
I’m sure you agree that the umbrella thorn is an interesting tree, but it is only the start. The bush is full of fascinating plants with interesting features and uses. I’ll bring you more posts on even more exciting plants in future.