Next to the giant saguaro cactus, these are some of the largest cactus in the Sonoran Desert. Before the world became aware of the limited nature of the desert flora, a common desert survival technique had the thirsty hiker cutting open a barrel cactus to get the moist interior. FALSE. I tried it when I was a teenager and didn't know better. It doesn't work. The interior is very bitter and the flesh of some types of related cactus causes nausea, diarrhea, and temporary paralysis. One thing about the cactus is true, it always points towards the south. The plants grow that way to prevent sun burn to their sides. These cactus are now a protected species.