Dierama robustum grows from 1 to 2 meters tall and is widespread at high altitudes in grassland in the Eastern Cape and the Drakensberg. It has pendulous large white to pale pink or mauve flowers and blooms in summer.ome species may bloom in a 1 gallon (3L) pot but most do much better in the ground where they have room to spread. Dierama dracomontanum is native to the Drakensberg Mountains of South Africa where it grows in grassland, sometimes dominating mountain slopes.