Multiple knob thorn stems so close together have an interesting prospect under positive growth conditions. Fusing as their bases probably have been from the start, the meeting of knobs and bark promises some self-inflicted torture known as growth pain if it lives, or whatever is stated in the autopsy report if it doesn’t. What slow phase or ceiling of growth may be involved here remains to be seen.
At this stage the picture presents a good idea of the shapes and sizes of stem knobs of Senegalia nigrescens. Each knob is prickle-tipped, the nearly black, hooked prickles grow in pairs immediately below stem nodes. Some young branches may be pale yellow where upper bark has flaked off.
More photos and information about S. nigrescens are furnished on this Site. Type the name into the Search Box on this page to see what that entails (Coates Palgrave, 2002).