Nemesia rupicola is a perennial, occasionally an annual herb with soft stems. It has ovate, toothed leaves that grow on short stalks. Some narrow white, vertical lines are visible low down on the upper lips of some of the white flowers in picture. The corolla has white (sometimes pale yellow) cushion-like humps at the base of the lower lip. Blooming happens from late spring to mid-autumn.
The plant is found from the southern Free State to Limpopo in much of north-eastern South Africa and Lesotho. It grows on rocky slopes. The photo was taken in Gauteng during May (Manning, 2009; iSpot).