Vachellia robusta is a variable tree, at least three subspecies having been recorded, two of which occur in South Africa. The one shown here grows in Gauteng, called V. robusta subsp. robusta (SA Tree List No. 183).
This is a small to medium-sized tree of up to 8 m with an irregularly spreading crown. The bark on old trees is dark brown, rough and fissured. The spines varying a great deal in length and thickness are white to greyish (Coates Palgrave, 2002).