Even though winter is a terrible time to be rooting cuttings, it can certainly be done. Simply because I take so many cuttings in the fall to reduce the size of my plumeria, both those that are brought inside in pots and those that are bagged, I have a lot that I try to root. This summer I switched to the bagged method, using moist sphagnum moss. Large diameter cuttings will be singly bagged and I'll have up to four cuttings in a bag if they have small diameters. So far, I seem to have better results with faster rooting using bags.
Though I use an oversized, 48"x20" heating mat, because my dozens of cuttings are stacked like a cord of wood, that heat really only affects those cuttings on the bottom of the stack. I supplement that heat with old-fashioned rope lights and use a 12' strand over and around the cuttings. LED won't work since those lights generate little if any heat. That rope light seems to really work well. Four weeks ago, I potted up 6 rooted cuttings, two weeks ago another 8, and then today, 11 more were potted.
So if someone tells you that plumeria can't be rooted in the fall and winter months, they don't know what they are talking about. Needless to say, because of our cold, it is a lot harder for me, than it is for those in sub-tropical areas (we have already had three nights in the low 20's and winter's just getting started
), but where there is a will there is a way.
