This is possibly the most cold hardy, edible citrus: Citsumaquat
It has that kumquat as one of the parents along with Satsuma mandarin and Poncirus trifoliata.
It has little fruits:
But lots of them.
And it survived -5F (briefly) in Oklahoma City. It got damage, but is now growing happily in Chattanooga, TN at my house. It has no trifoliate taste. It basically tastes just like a kumquat. It was breed by Don Moorehead in Oklahoma City. He has had many other citrus hybrids survive but the fruits always have had at least some trifoliate flavor until this one.