Yes, there are a lot of hybrids. Musa basjoo is cold hardy to -20 F so I am considering it the most cold-hardy that people here will grow. Sorry if I didn't make myself clear. The USDA zones are US zones.
Back to the question and topic of the thread. For the purpose of the database we need to make sure that people have a relatively accurate idea of the cold-hardiness of a plant. With M. basjoo, it's far hardier than zone 9. I want the database to be as accurate as possible and I believe people know the various zones contain micro-climates with them that don't fit the exact parameters of the temp range. It may not be perfect but it's the system we have to work with here. I think clarifying is better than than not. But that's just my opinion.
