I have to say that of all my plants my epi-cactus Selenicereus have to be the hardiest. I have seen these actually save their own lives. The roots had rot and it was creeping up the stem and at the same time it threw a branch out and it grew over to the next pot, laid down on the soil and threw roots into it after a small established root system developed it let go of the rotting stock and had become its own rooted cutting and eventually mature plant. I also have a Trichocereus (Peruvian torch cactus) that has sat in my attic for over 2 years with well over 100 F. in the summer. No water, no soil, no light; just a cutting. It is still alive and ready to plant any day still and people manage to kill 'em.