Posted this before but couldn't find it. Anyway, I have my mandevilla overwintering in cool basement. Cut back and basically dormant right now, but I lifted it and robbed a rhizome from the plant which I put in a pot with regular potting mix and brought upstairs. Now, what is my chance that this will shoot new growth from just that rhizome (with lots of small hair roots) or is it just wishful thinking? What procedure do I follow to coax it into growing? Got the plant at Walmart a couple years ago and cut it back and overwintered it in cold garage last year till late January or Feb and then brought it in and it took right off. Want to keep it going because it has double flowers and was the only one that I saw when I bought it. Tried rooting cuttings in the fall but they all died - wrong time of year for that, I guess.