The Garden lies in a sub-tropical area and summer temperatures have often been known to reach 34o C. The annual rainfall varies but averages about 750 mm, mostly in the summer months, there being no rain at all for six to seven months of the year.The Garden opened in 1946 with 50 hectares for Garden development, 15 for buildings, nurseries and experimental areas and 10 ha for a nature reserve. Dr R A Dyer was able to obtain so much of this prime land because of the poisonous plant, Gifblaar, Dichapetalum cymosum. The Garden was the natural habitat of this plant and made the land unattractive to farmers.The intricate wrought-iron Main Gates and Reynolds Gates, designed and made by the late Hans Brugger, serve to complement the natural beauty of the Garden.

The Garden includes six main vegetation types and roughly 1 700 species of flowering plants. More than half these species grow naturally in the Garden. The rich variety is ascribed to the fact that the rocky Silverton ridge divides the Garden into Highveld and Lowveld regions. The natural vegetation common to Pretoria is ‘Bankenveld’, a mosaic of grassland and savannah, interspersed with dense bush on rocky ridges, in ravines and along streams.