You have to pick the right host cactus 🌵I know that much and the right size. That one looks a little big. Keep it inside in a window with good sun or grow light till the moon cactus root makes it through the host cactus and makes it to soil. Couple months or so. They don’t like it real cold. Ask google for the rest.
@docthrill , Echinopsis pachanoi is what's used in NZ(and pereskiopsis but I don't have any of that) due to hylocereus tending to rot in our cooler climate. I've got it on a NE windowsill under cover with a heat pad keeping it above 18celcius. Um grafting doesn't involve the scion putting roots through the rootstock, the vascular rings of both plants connect up and become one, so that the scion is fed by the rootstock, because it has the chlorophyll that the scion /varigated gymnocalycium lacks
Yeah, they can’t live without a host. Moon cactus doesn’t produce chlorophyll. You have done the researcher. I left mine in the garden house last winter and the host cactus turned to mush like you said. I didn’t research that till after they mushed. Lol