Wanted to say that after talking with many people and doing trials myself, I now come to the conclusion that yangmei will do well in zones 8 and up. Now I don't know the max though as chill hours seem to be required. I know many people who are hesitant to try yangmei down in south FL and PR as the lack of chill hours may be a problem. Now, there are many cultivars, so I think it's only a matter of time till we find one that does well in tropical climates.