>>1303278Will do but i can tell you right now it's probably not worth the effort. (I have no idea about citrus, I'm only talking about cool temperate fruits which grow in the UK).
You will have to interstem graft with certain compatible varieties to get apple and pear on there. It will take many years and will be very technical. Even if it seems to work, after four or so years you can get delayed graft incompatibility and, grafts can then die.
Left hand side is a real manticore of a tree, with not much more you could squeeze on species wise. I believe the Mexicans cultivate some sort of crataegus for fruit which is probably graft compatible with hawthorn (though possibly not functionally compatible given the different climate requirements). I also heard the Germs have bred a rowan with large non-bitter fruit which is probably graft compatible with whitty pear, so there are two more potentials (not counting freak hybrids like sorbopyrus).
If you haven't grafted same species trees before, don't even try this desu.
As the other anon said. You are probably better off grafting multiple different varieties of the same species onto a single tree. Pick on the right is an example of this I might try myself (may reduce the rootstock to M26 and have one or two fewer varieties). Such a tree should graft very well and you will have a varied selection of apples which ripen at different times giving you ripe desert fruit spanning from Mid September to Early November.
