Granny Smith Apples
 

Just got a Granny Smith apple tree. Always enjoyed them and now live somewhere where they can grow. I have read that they are self fertile and will produce without another apple, and others saying that it needs another apple to produce well. Does anyone have any experience.

Will definitely produce better with a pollinator tree

What about a 3 in one Espalier. It has honeycrisp sweet 16 and zestar. Think it would cross polinate well?

Don't know of those varieties in Australia, but if sold commercially as the triple graft, it should be good for pollination. You may find that one of the varieties will put grow the others, you will need to prune to balance the tree.