Copiapoa calderana (syn. C lembckei var. magnifica)
A variable species native to Chile, this cactus grows as a solitary stem or as clumps. It can reach 30 cm in height and 10 cm in diameter, and has yellow flowers which bloom in Spring and Summer. It prefers a sunny position in well-draining soil and should be protected from extreme heat and cold. Water regularly in Summer, allowing the soil to dry out in between waterings, and keep dry in Winter.