They would certainly bloom to overlap at least somewhat, if not entirely, even though Connell Red has late ripening fruit and Sweet Sixteen is mid season. In addition, all crabapples will pollinate apples. Especially in Mpls/St. Paul, there are so many apples and crabapples grown that one would not even need a pollenator tree in their yard. At least that's the way it has always been. If honeybees ( apple's major pollinators) become not as plentiful, it might become a factor. The Snow crab produces healthy, viable pollen. It does not fruit due to its female parts, and will pollinate apples just like any other crabapple will.
