Well, two things to start....Its alittle early to plant in your zone unless its a very warm April. Cavendishes don't like chilly nights. I suppose you can cover them up...Also your location looks like its a bit tight. Is this area a micro climate? 'Dwarf' cavendishes can still get pretty big btw. You will probably never get fruit in your zone. They do overwinter well indoors. A greenhouse could help in fruiting. If it were me I would plant in early May (depending on long range forcasts) and consider a more roomy location. The musa bajoos will also need some room and try to avoid the temptation of bringing them in this fall. Keep this variety in ground. All your bananas should get better each year. More pups/taller. Hard to say what you will get this year...I have attached a photo of a musa basjoo that is a couple years old. I have to move this year cause it has out grown its location. This puesdostem(several) are easily each bigger than basketballs. Basically, a Bobcat dozer would be nice about now. Here is a link that might be useful: musa basjoo

I'm actually trying to get a banana to fruit in a 24" pot (roughly 28 gallon volume). I bought a Dwarf Cavendish because all the vendors said it was the *only* cultivar I'd have a chance of fruiting in a pot. I know it works because I've seen them fruiting in pots before. I think it just takes huge volumes of water, fertilizer and sunlight. I am, however, bringing mine indoors during the winter. They don't like cold.

Darren, SDC is pretty bad about getting "cigar end rot" which will cause the fruit to do what you described. I had it hit one of mine last year. I don't have any images of it but I think there are some on the web if you want to confirm it. I think you can control it with fungicide applications after bloom fall but I have never tried. Sorry to hear about your loss, GATrops

Do you have them in pots? since it will be warming up again and your attic wont be cool yet, they will still be active. Just keep them watered regularly and set them outside in partial sun since its going to be in the 70s still and then next week the forecast is going to be in the 60s with lows in the 40s. You shouldnt have to put them in the attic yet because it wont be cool enough in your attic for them to go dormant. When it starts getting really cold and we experience more frosts then you can set them in your attic to go dormant.