Moon Cactus, aka Gymnocalycium mihanovichii or Hibotan cactus, is a mutant and lacks the ability to produce chlorophyll, which means it must be grafted onto a rootstock with that ability. It is often grafted onto the Hylocereus cactus, and the combined plant is called a "Moon Cactus”.
Although they are not poisonous, watch out for their sharp spines! Cacti are a great starter plant or gift as they need very little water and will thrive in full sun. They would much rather be too dry than too wet (think of desert conditions when taking care of them).
