I've never done it but apparently if you graft branches of different varieties on one tree, you can produce a number of different varieties of apples on one tree. This would be especially good if you could get some of the tastiest heirloom varieties.
We haven't been doing that for now. The success rate doing so is somewhat less than directly grafting the whole top of the tree onto rootstock, for a few reasons. Since our primary goal is preservation and a lot of these trees have zero clones and could be wiped out by wildfire on any given year, our first priority is to get clones of every tree.
