Bishop’s Cap, Star Cactus is very popular and widely cultivated. Five other species of Astrophytum are also often grown as house plants. The illustrated variety, tetragona, has only four ribs. The generic name, which means star-like plant, is derived from Greek and describes the shape of this, with five to eight pronounced ribs that form the . At first the body is globose, growing taller later and becoming columnar in age. It is without spines and covered entirely with white, felted spots that prevent the evaporation of water. The form nuda does not have felted spots and so its stem is green. Spaced along the edges of the ribs are large woolly areoles without spines. The , which arise in the shallow depression on the crown, are large, 4-6 cm in diameter, and coloured pale yellow. The filaments, anthers and seven-lobed stigma are also yellow. The are large and brown. Propagate from , not by grafting.