That's a very healthy looking banana!! It's beautiful
It looks a lot different than my Super Dwarf Cavendish though, I think it's something different. I looks more like pictures of 'Little Prince' banana.
My Super Dwarf Cavendish has the traditional Cavendish 'wine stains' on the leaves especially when they are young. Also the stem gets black spotting and pink coloring like my regular Dwarf Cavendish does, yours is solid green.
As far your question, my bananas stop growing when the temps get to around 50F. I would wait for it to warm up some more before you put them on the ground.