Question
We don't expect it ever to fruit, but a random pit thrown out front in our garden area generated a small bush/tree.  It has made it through several winters here in Northeastern Florida near Jacksonville, with some nights the temperature dropping to the teens.  Sometimes we'll wrap it with a plastic bag to help it survive.  

However, the central trunk died maybe a foot above the ground a couple of years ago and we just cut it off.  Five or six branches have come out below the cut over the years and branch out and upwards 3-4-5 feet.  I'm trying to understand what is going on with the trunk below that cut.  I wonder why the entire tree didn't die when I cut off the central trunk.  Also, if we do keep it going, is there a chance the branches we have left will indeed fruit at some point?

Answer
What you are seeing Art are suckers from the roots, which will never amount to anything; if the main trunk died the tree for all intents and purposes is done. The suckers are growing up from the root stock and may or may not continue to develop, but because of the demise of the grafted (surface) tree it would be much more advisable to  plant a nursery bought Mango of the type you desire, not the undesirable root stock. Mangoes are 10a and higher climate zone fruit trees also, and you are way to cold up there to get one to make it through the Winter. Nick