Moraea polystachya, the Karoo iris, is a deciduous perennial that grows annual aerial parts to heights of around 80 cm. The corm grows to 4 cm in diameter, covered in a dense net of tough dark fibres. The tuft of roots below the corm is contractile, i.e. they pull the corm deeper into the soil, as far down as 30 cm, adding to its protective underground positioning.

One to five long, narrow leaves grow annually from this corm. They range between 20 cm and 70 cm in length and up to 1 cm in width. The leaves sheath the flowering stem (Manning, 2009; Vahrmeijer, 1981).