Winter storms and arctic cold events can be damaging to trees and shrubs. Remember to inspect your plants for broken limbs or lodging over in soppy wet soils after storms. Make clean cuts when you find broken, torn, or split limbs. Clean cuts will be less susceptible to fungal infection than ragged breaks.
If you have lost the top of a more recently planted tree you may be able to train a new top for it. If the break occurred above the graft, and above a flexible side shoot, you can train that shoot to be the new leader with a splint. Make a clean diagonal cut ¼” above the side shoot, tie a piece of bamboo or other stiff material to the trunk in two places below the shoot, then carefully bend the shoot upwards and tie it to the bamboo in two places, to create a new top on the tree. If there is no flexible side shoot available, but the break is above the graft, make a clean diagonal cut ¼” above a bud or node, and cut back any non-flexible side shoots within 6” of your cut to one or two buds. In the spring after the new growth is out about 6”, select the strongest most vertical shoot, remove the others, and splint as necessary to keep the shoot straight.
Sometimes newer trees break off at the graft or below, in that case there is not much you can do. All you have remaining is the rootstock, which you can either allow to grow a new top to graft onto, or remove and replace with a new tree.
If your tree has developed a strong lean, or has fallen over, you may be able to help it re-establish its upright habit again. If the roots did not come out of the ground, place a prop against the trunk or under a sturdy limb and push the trunk straighter. A big lean may need to be pushed back up in smaller increments, to avoid causing any further root damage. Sometimes snow weight puts a bend in the tree. If the trunk is not too thick you may be able to push it back up straight. The tree will need help to stay upright, secure a sturdy metal rod or 2x piece of wood to it. Tie the splint to the tree in two to three places below the bend, and within and above the bend so the splint holds well. Keep the splint on for at least one growing season.
If the tree has leaned almost to the ground, or completely fallen over, most likely the roots on the opposite side have either broken off or pulled out of the ground. Before trying to straighten the tree dig under the roots on the opposite side to make a hole the roots can settle back into when you push the tree back up. Cover the roots with soil after you have righted the tree. To balance the top of the tree with the root damage it is best to prune the top of the tree also, up to 50% of the top of the tree if there was a lot of root damage. Make more thinning cuts than heading cuts, leaving as many terminal buds as you can which will send the message to start growing to the roots in the spring. Stake the tree, using 2-3 stakes, protect the trunk with rubber strips (or something similar). Leave the tree loose enough to be able to move an inch or so in any direction, but not much more. Remove the stakes after one season if the roots were not broken, after 2-3 seasons if there was a lot of root breakage (to give the root system time to fully re-establish).