Melocactus azureus AKA Turk's Cap is a beautiful light blue bodied barrel cactus that stays relatively small until it matures with a cephalium on top. The cephalium is part of the body that forms a tightly knit crown of spines in which the flowers open. Researchers have determined that it protects the flowers from unwanted invaders, but assists correct pollinators in finding the open flowers at night. You are bidding on the plant size shown.