Although some succulent species are considered dangerous, others have medicinal and therapeutic properties you might find useful. For example, the stem joints for both the cholla species and the prickly-pear cacti are very weak. There are so many cacti species that you will find unexpected (pleasant) surprises every now and again. The Devil's head Cactus is one of over 1700 surprising (species). You can make the story even more interesting by adding rare, exotic species. Your seeds should be sown in a well-draining soil mix towards the end the cold season.