Thulin, M. (1993) Fabaceae, Flora of Somalia 1: 1-465
Plants trees, 5-10 m tall; young branchlets grey to grey-brown, glabrous in Somaliland and Somali, epidermis not flaking. Stipular spines straight or nearly so, usually short and up to 8 mm long. occaionally up to 6(-11) cm long. Leaves usually borned on distinct cushions; pinnae (2-)3-8(-10) pairs; leaflets 9-27 pairs, most 3.5-7.5 mm long and 1-4 mm wide, usually glabrous. Inflorescences pedunculate heads; peduncles 1.2-5.4 cm long; involucels from near the base to 1/3 rd the way up the peduncle Flowers white; calyces 1.5-3.2 mm long; corollas 3-4 mm long. Pods 7-19 cm long, 0.7-3 cm wide. straight to falcate, dehiscent, brown, longitudinally veined, glabrous; seeds compressed, 8-15 mm long, 5-9 mm wide, areoles 6.5-9 mm long. 3.5-6.5 mm wide.
Vachellia robusta is an African species with three subspeces, Vachellia robusta subsp. robusta, Vachellia robusta subsp. usambarensis and Vachellia robusta subsp. clavigera, Vachellia robusta subsp. usambarensis extends from Mozambique to Ethiopia and Somaliland, Vachellia robusta subsp. clavigera extends as far north as Kenya, and Vachellia robusta subsp. robusta only as far north as Zimbabwe.