How long can I leave the bark on the sunny side of my young tree is cracked, sunken, and peeling off before it becomes dangerous?

Whether it can still be saved

Often, if the dead strip covers less than about a third of the circumference and the tree is otherwise healthy — it will close the wound itself. Do not cut the bark back with a knife to clean the wound, do not apply sealer, and do not push fertilizer at it; water through summer drought, keep it mulched, and give it time. Prune out branches that have died back above the scald. It is not savable when the scald has girdled the trunk, when borer holes and frass appear in the dead face, or when the trunk sounds hollow — a young tree that far gone is cheaper to replace than to nurse. Prevention is the real product: light-colored crepe tree wrap or white latex trunk paint applied in late fall and removed in spring, for the first few years after planting only. Wrap left on year-round holds moisture against the bark and causes its own damage.