The fever tree – Vachellia xanthophloea

Kruger National Park | May 2019

“Go to the banks of the great grey-green, greasy Limpopo River, all set about with fever-trees, and find out.”
In Rudyard Kipling’s book “Just So Stories”, in the tale titled “The Elephant’s Child”, the Kolokolo bird sends the curious young elephant to the Limpopo River where he can find out the answer to one of his numerous questions… What does the crocodile eat? This story explains how the elephant got his long trunk and it is a great, fun read.

The fever tree is a really obvious plant where it grows in low-lying swampy areas or nearby rivers in the bushveld. It is a beautiful tree with its golden bark and long white thorns. It is one of the trees that was previously known as an acacia (although the genus name was recently changed to Vachellia – named after Rev. George Harvey Vachell (1798-1839), chaplain to the British East India Company in Macao from 1825 to 1836, and a plant collector in China). The species name xanthophloea is derived from the Greek words xanthos, meaning yellow, and phloios, meaning bark.

In the early 2000s it was decided that the genus “Acacia” needed to be split up and was not monophyletic (they did not come from a common ancestor). Due to the large number of wattles species that occur in Australia it was deemed easier to change the name of the thorn trees than to change the name of all the wattle species and, therefore, the thorny trees that used to be referred to as acacias were then split into two groups (mainly based on the shape of the thorns). The old acacia trees that have straight thorns are now listed in the genus Vachellia and those that have hooked thorns were placed into the genus Senegalia. This has caused much
consternation amongst botanists and tree enthusiasts, particularly since in ancient Greek the word “ακη / ake” meant “thorn / point”, which the majority of wattles do not have.

The most obvious characteristic of the fever tree is its golden branches and trunk which have been described by various plant collectors as “evil, pallid, leprous, sickly and sinister” – (quoted from “Trees of Southern Africa by Keith Coates Palgrave”). In my opinion it is none of these, but rather stunningly, radiant and beautiful.

The trunk and branches are however not yellow or golden, but green in colour that have a powdery layer that is bright yellow in hue and that gives the plant its characteristic golden tint. When you rub your hands over the trunk you will notice the yellow powder that coats your palms. This powder has been used by various tribes in Africa as a form of sun-protection and is also sometimes used to enhance their looks (as a form of make-up), particularly when going to important dates such as when going to an interview etc. The powder when applied to the face supposedly makes the person glow and makes them seem more friendly and out-going. The green bark and trunk enables the tree to photosynthesize through these parts as well as through the leaves and it is because of this ability to rapidly produce food for the plant that enables it to grow quickly and to regrow after elephants damage them (elephants find this tree to be highly palatable).

The name of the fever tree supposedly comes from the early explorers who came to Africa in search of gold, slaves and ivory. Before there were maps of the interior of the “Dark Continent” these explorers and slave-traders needed a way to get back to their ships that were moored at the coast. They thus followed the rivers to the villages and then were able to follow the rivers back to their ships. Rivers are places where Fever Trees grow. Rivers are also places where mosquitos are plentiful. While following these rivers many of these explorers contracted malaria. Since they did not know what was causing the fevers and disease that they were experiencing, and because they noticed that they got sick whenever they were in areas where these trees grew, they attributed their illnesses to the tree itself. The tree was therefore referred to as a fever tree. Funnily enough, numerous tribes use the bark traditionally to treat fevers and eye infections. Medicinally, the roots and a powder made from bark stripped from the trunk are also used as an emetic and as a prophylactic against malaria.

Fever trees are fairly tall trees, reaching ten to fifteen meters in height. As with most, if not all, species from the Mimosoideae sub-family they have bi-pinnately compound leaves (leaves that are divided to form leaflets known as pinna, which are then divided again to form even smaller leaflets known as pinnules). Fever trees have long, white, straight thorns typical of all Vachellia species and have bright yellow, fluffy, pom-pom like flowers.

As with all species from this family the seeds are enclosed in pods and these plants are therefore considered to be part of the pea family (legumes). Legumes are plants that often have a symbiotic relationship between their roots and a host-specific strain of bacteria known as rhizobia, which enables the plant to utilize the nitrogen in the soil which otherwise would be unusable. When these plants die the fixed nitrogen is released, making it available to other plants and this helps to fertilize the soil. These leguminous plants are thus very important to the environment in which they live.

We are very fortunate to have quite a few of these magnificent trees growing in the Singita Kruger Park concession and they add quite a character to the magnificent landscape.