Vachellia is a genus of flowering plants in the legume family, Fabaceae, commonly known as thorn trees or acacias. It belongs to the subfamily Mimosoideae. Its species were considered members of genus Acacia until 2009. Vachellia can be distinguished from other acacias by its capitate inflorescences and spinescent stipules. Before discovery of the New World, Europeans in the Mediterranean region were familiar with several species of Vachellia, which they knew as sources of medicine, and had names for them that they inherited from the Greeks and Romans. The wide-ranging genus occurs in a variety of open, tropical to subtropical habitats, and is locally dominant. In parts of Africa, Vachellia species are shaped progressively by grazing animals of increasing size and height, such as gazelle, gerenuk and giraffe. The genus in Africa has thus developed thorns in defence against such herbivory. The members of Vachellia are trees or shrubs, sometimes climbing, and are always armed. Of the 163 species currently assigned to Vachellia, 52 are native to the Americas, 83 to Africa, Madagascar and the Mascarene Islands, 32 to Asia and 9 to Australia and the Pacific Islands.

Vachellia sieberiana, previously known as Acacia sieberiana and commonly known as the Paperbark Thorn or Paperbark Acacia, is a tree indigenous to southern Africa. It is used in many areas for various purposes. The tree varies from 3 to 25 m in height, with a trunk diameter of 0.6 to 1.8 m. Vachellia sieberiana is valued largely as a source of forage, medicine and wood. The inner bark is a source of fibre purposes such as stringing beads. The gum is edible and both livestock and game animals browse the tree and feed on the dropped pods, spreading viable seeds in their dung. The flowers of the tree make good forage for bees and bee hives are put directly in the trees to exploit the resource. The leaves of the tree commonly release toxic chemical compounds when the tree has been heavily browsed, some of the compounds may release hydrogen cyanide when ingested, which may be lethal to cattle. The fallen pods and foliage can provide lifesaving forage during dry times of the year. The gum of the tree is used as food, as an adhesive, and as an ingredient in making ink. In Africa, the bark or root is used to treat urinary tract inflammation. The bark has astringent properties and it is used to treat colds, cough, and childhood fever. According to the World AgroForestry Centre, “A decoction of the root is taken as remedy for stomach-ache. The bark, leaves and gums are used to treat tapeworm, bilharzia, haemorrhage, orchitis, colds, diarrhoea, gonorrhoea, kidney problems, syphilis, ophthalmia, rheumatism and disorders of the circulatory system. It is also used as an astringent. The pods serve as an emollient, and the roots for stomach-ache, acne, tapeworms, urethral problems, oedema and dropsy. Vachellia sieberiana is a legume and like many legumes it hosts Rhizobium bacteria in its roots. The bacteria fix nitrogen gas from the air and, without requiring nitrogen fertilizer or soil nitrates; they convert it into nitrogen compounds necessary for plant nutrition. Ultimately, surrounding plants also benefit from the increase in available nitrogen, which means that plants such as Vachellia species are of particular ecological importance.