The biggest ones I've grafted so far have been about 3" diameter, maybe 4". Once they get big enough so that the bark gets rough, they're really hard to do.Thought I’d bump this as it’s very interesting , I’m about to take your advice and do a google search and try to learn more, hillbilly what is the biggest tree you’ve cut down and grafted I have some males as big as your leg and do u just take your cutting at the rt time and put it against the trunk and wrap it with the parafilm or do u remove the bark and what do u put on top of the tree u cut down, sorry for all the questions, but I’m definitely gonna try this, this year
In order to get grafts to take, you have to keep the cambium layers of the rootstock and scion in contact. That, and timing and not letting anything dry out at all are the keys. What I have been doing with the persimmons is bark grafting. You cut the scion wood in the winter when it's dormant and keep it in the refrigerator to keep it dormant. Then, you wait until the rootstock is fully leafed out and the sap flowing, so that the bark will sli[. You saw the rootstock off, then carefully make a vertical cut a couple inches long and seperate the bark from the wood. Then you cut the base of the scion in a wedge shape, and force it between the bark and wood, then wrap it. You need to apply something to the wound to keep it from drying out. Grafting wax or non-silicone caulking work well.
There are several bark-grafting videos on Youtube, a video is worth a thousand words.