Basjoo gave up the ghost here, even kept inside over winter! After a couple of cold summers with temperatures mostly between 14-16C I guess they didn't have the will to grow and flourish, bananas stop growing at those temperatures.
I still have a lone Musa sikkimensis I grew from seed which is hanging on, it does better here although it's not that great, I bring it inside over winter now I'm down to one. If we have warmth in spring that does help if put in a greenhouse but springs of the last few years have been lousy too, at times 4-6C in April.
Spring often doesn't roll on until three weeks into April, then it can be sporadic. Zones don't reflect the growing season or maximum temperatures, they only reflect the expected minimum which puts us in zone 8a although every 20 to 30 years we get an exceptionally cold winter as we had last winter with temps. at or below freezing for 7 weeks and down to -17C at night.
The tall and short of it is you need a good long season and more warmth than we get for any Musa to grow and survive. There's a hardier one which the species escapes me now, the local garden centre had some surviving outside in the ground but last winter killed just about everything they had.
