**1. Introduction**

*Vachellia karroo* is a highly useful tree that is widespread throughout Africa [1], and it is the most widely distributed tree in South Africa [2]. It belongs to the family Fabaceae (Legume family), which is one of the largest woody plant families in southern Africa. Species of the *Vachellia* genus vary in their distribution range; there are species that are very widely distributed and occupy a diverse range of habitats, while others have a very restricted

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distribution [3]. The species are a prominent feature in the Savanna biome (bushveld) in South Africa but can also form local dominant stands in other biomes such as the Grassland and Nama-Karoo biomes. Those with a broad distribution range, like *V. karroo*, occur in several biomes [1].

The *Vachellia* species are pod-bearing woody plants that range from shrubs to large trees. They can be sprawling or climbing, and this character differs with habitat [4]. This genus in Africa is readily recognised by its thorns, which are typically paired and straight. These thorns are modified stipules, which become hard and spiny [1, 5] and are important for identification of the trees [6]. *Vachellia* trees can further be distinguished by their characteristic growth form, by bark, and also by pods. This is however a taxonomically difficult genus containing a number of closely related species whose recognition and identification are not always simple [3, 5].
