Encouraging suckers

Is it possible to encorage a tree to send up suckers in a chosen spot?

There is an apple tree in my yard which not only suckers next to the main trunk but also in several places a meter or so away from the trunk.  One such is in a spot where I was planning to plant a tree anyway, so now I can just graft to the sucker and save myself some time and money!

I'd like another tree about the same distance on the opposite side of the old tree, but there are no natural suckers there.  The old tree suckers quite strongly in undesirable spots.  Is there some way I could encorage it to sucker in the desired one?

Hello, Tom.

I think suckers grow where the sun touches the bark. So the way to encourage these suckers would be to prune the tree where it shades the bark. It works with the fig tree, but I don't know if that's the case with other tree species.

Suckers, to me, refers to shoots growing from the roots rather than the bark (which I would call watershoots or epicormic growth).

Epicormic growth is an indicator of stress in trees (and is currently one of the best symptoms to diagnose the ash dieback epidemic over here).

Assuming that root-suckering can be triggered in the same way, perhaps under-watering, removing leaves or otherwise stressing a tree might force it to sucker. I have also heard that some Prunus species (plum in particular) will sucker heavily when pruned hard which I feel somewhat corroborates this.

I've caused apple root suckers to pop up by digging a hole that chops thru a root, and leaving the hole unfilled. The chopped end of the root, where it's exposed to the air, will put out a leafy shoot. I dug up and transplanted one a few days ago.

I too have had some fruit trees (Evans cherry in particular) sucker like mad where roots are damaged.

Thanks for the replies!
Yes, do indeed meen suckers from the roots.  So it sounds like I should dig around the spot I want a sucker and hope to hit a root.  Hopefully that will give me a sucker that in a few years I can graft to.
The second part of this question.  Is this a good idea?  Are there disadvantages to having two or more trees sharing the same roots?