Fairy castle cactus: what a fantastic name! Can’t you just imagine dust-sized fairies dwelling in the clustered towers of this plant? In its native habitat of Brazil, this species can grow to over 6 feet (2 m) tall. You can vary the number and height of your stalks to make your fairy castle as petite or as grand as you like. The white dots on the stems are called areoles. The grow in an attractive three-, four-, or five-point star from the tip of the stalk down the sides. To keep things simple, this pattern makes stems with four spiny ridges.