I've never heard of tropicals that will live as perennials in Maine.

Hi, I'm in Portland and last summer planted an 'ernest wilson' mimosa tree, or silk tree-something I've never seen in Maine before. It grew about 5 feet last year and survived the winter ok. That particular type is supposed to be hardy to -15. They have really tropical leaves and pink pom-pom type flowers and bloom for about 2 months. I suppose that if you wanted to try cold hardy palms or bananas, why not give them a shot! Hey you might as well go for it.

My banana tree after 2 years died...I am sad to admit that I feel it was due to my neglect (Not available to give it that little bit more attention it needed but I wasnt able to give it to it)!(