Black thorn acacia (Acacia mellifera) is a deciduous shrub or small tree characterized by sharp thorns, a rounded habit and sweetly fragrant flowers. The tree is native to Namibia and occurs throughout much of the country, even growing in the harsh Kalahari Desert. The genus name "Acacia" comes from the Greek word "akis," which means barb or point, while the species name "mellifera" translates to honey-bearing.
The black thorn acacia may grow from anywhere to 6 1/2 to 26 feet tall, showcasing black bark that lightens to grayish brown on the branches. Branches are lined with pairs of sharp, hooked thorns and stems topped with silvery green, elliptic leaves that showcase small white hairs on the margins. Clusters of creamy white flowers appear from August to October, giving way to papery brown pods. Interestingly, flowers are most fragrant at night according to the World Agro Forestry Centre.
In its natural habitat, the black thorn acacia is tremendously attractive to wildlife. Animals such as giraffe, springbok, camels and goats browse the protein-rich leaves, while butterflies such as the silvery bar and the obscure saphire flock to the flowers. Bees come to the tree in the mid afternoon and late morning to forage, creating a clear, slow-to-granulate honey that the World Agro Forestry Centre describes as excellent and high quality. Broken stems secrete an edible gum that is enjoyed by animals, birds and children.
The hard, attractive heartwood of the tree may be oiled and polished to a shiny black sheen. The heartwood is resistant to termites, according to Plantz Africa. In Namibia, the timber is often used for fuel, timber and huts, while the branches are used for fencing and the twigs are used as toothbrushes. Bushmen of some tribes mix the sap of the tree with powdered grubs to create a potent poison for their arrows. When pruned, the black thorn acacia makes for a dense shade tree.
Black thorn acacia is a suitable tree for U.S. Department of Agriculture plant hardiness zones 9 and above, handling low temperatures in the 20 to 30 degree Fahrenheit range. The tree requires full, direct sunlight and deep, rocky or sandy soils that are exceptionally well draining. Seeds germinate best when they are soaked in sulphuric acid for up to 15 minutes or boiled and left to soak for 24 hours. Germination generally occurs in about five days. Black thorn acacia is very drought tolerant.