Good Morning Thomas, 

Thank you for contacting the U of M Extension Service. 

Interesting dilemma! From your photo, I cannot see the canopy. You might consider why the tree lost it's leader. Was it watered during the past few drought years? Were you involved in the planting of the tree? Could it be a problem with stem girdling roots? What does the ground around the tree look like? 

I would suggest waiting until fall. Identify the branches that are thriving and healthy. If one of them starts to stand out as a leader, you could prune back a part of the branches that will not be the new leader to give the leader a head start. 

Here is a link about pruning trees from the U of M Extension Yard and Garden website: 

https://extension.umn.edu/planting-and-growing-guides/pruning-trees-and-shrubs

If you scroll down, there is detailed information about pruning young trees. 

Adding a few inches of wood chip mulch, a few inches away from the trunk, out to the end of the drip line will keep the soil cool, hold the moisture and protect the roots. 

Good Luck!