A neighbor has a mid-size swingle tree - four main trunks each in the range of 3-4" in diameter and ~15' tall, - that they would like to convert to something edible. A recent attempt at top working one of the trunks using a cleft graft was unsuccessful. I believe the issue was an excess of moisture (we, like the rest of the southeast, have been inundated the past few weeks, and I had just cut the top off the trunk when the skies opened up). Any suggestions on how to best seal the top of the rootstock - wax v tape, e.g. - would be appreciated. I've never attempted anything over 1/2" or so before, so more general suggestions for cleft grafting larger-diameter trees would also be appreciated - methods for prying the the cleft open while inserting the scion, whether to look for scion of a particular diameter based on the rootstock diameter, etc... Or if folks recommend bark grafting instead, I could try that, as well.
Thanks,
ES

With a large diameter like that, I would try bark grafting instead of cleft grafting.