Normally I'd cut off those little suckers, but....
I have a spring snow flowering crabapple that has not grown very much in 5 years. I have another that's going gangbusters. I pruned the non-growing one and POW!, it send off suckers instead of new growth. They're growing very rapidly. I'm considering leaving them alone. The suckers are already more than half as tall as the original trunk.
An earlier post of mine I talked about pear trees getting girdled by bunnies. One has made it, the other has not however it is sending up new trunks. The tree is not grafted. It's an Asian pear.
Is it worth waiting? I'm very patient