Answer: Because it has such a different growth/perfomance pattern, I wonder if the rampant branch springs from a bud just below the graft union. Check again, and if this is the case, go ahead and prune it off a little later this spring. The only other thing that comes to mind is that the tree was mislabeled, and has two different varieties of cherry budded on a single rootstock. Check with the nursery where you purchased the tree to find out more. Hope this helps!
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