Astrophytum myriostigma, Bishop's Mitre Cactus, is native to northern and northeastern Mexico where it occurs at altitudes of 750 to 1,500m on very free-draining calcareous substrates. It is famous for its spine-free geometric five-ribbed shape and although some forms do have four or even three ribs, the five-ribbed star shape is the classic Astrophytum myriostigma form. Starting life as a chunky globular plant, Astrophytum myriostigma gradually becomes columnar with age and tall venerable specimens are highly-prized. It freely produces flowers in the summer that are pale yellow and slightly fragrant. The body is covered - to greater or lesser degree - with small white trichomes, tiny patches of microscopic hairs.