My wife got this little tree (maybe in a pint sized container) last winter. This thing wasn't more than six inches high at the time. It's been growing rapidly ever since. The pot it's now in, I believe, is a 7.5 gallon size. I must water this plant everyday, and I think it's getting root bound. In any event, I will keep it in my greenhouse over the winter, but I'd like to plant it out come spring of 2012. My question is, what is the cold/frost hardiness of this tree? I can't seem to find much