Floridian said: Grafting question:
What is the center, base cactus used for this? Would love to try making one with Christmas cactus 
Hi suspect it is one of the Hylocereus, it would be unlikely to be Hylocereus trigonus, used extensively in South Korea,
Production and Breeding of Cacti for Grafting in Korea as I have not come across anyone locally who has a grafted scion, on H trigonus, for any lenght of time.
What you need is a fast growing Hylo species so it may pay to collect a number of species and select one which has the properties you need.
Unfortunately Kada's Garden has dismantled their website, have found no mention on the site of the Hylocereus used. There is a good guide however at
How to properly graft to Hylocereus root stocks., you might try
contact.html and see if you get a reply.
You will notice the seedling scions I am grafting, are on a fast growing species and am using fresh shoots together with Graptopetalum species leaf mucilage.
For field work stop at or just before, the Autumnal Equinox starting again after the Spring Equinox when new growth resumes.
Notice in your first photo, the removal of areoles not being used, encouraging both initiation of new shoots or reduced competion for scions to be grafted.
Let us know how you get on.
Cheers
