Moon Cactus with red top: See how the bottom, green portion of the plant shows healed, diagonal cuts, from when it was grafted to the red top.
How To Graft Euphorbia
Fascinating video on how grafting is done!
In Dutch, but you can select CC for text in your own language.
Moon Cactus grafting is accomplished by making convex, v-shaped cut at the top of the Hylocereus
base, by using a sharp, sterile knife to diagonally cut off the top of each of the four sides. To prepare the scion (top), cut a concave, v-shaped in the underside of the moon. The white juice of the Hylocereus base should be cleaned off with water before putting the plants together.
The newly cut sections are then joined together using rubber bands. If the graft takes, the two plants will heal together, into one.