I am leaving my chinese elm and my bougainvillea out a little longer because I want to push them into at least a short dormancy. You see, I need my sunroom to temporarily house the trees that belong to the business and are making the transition from the wholesale greenhouse to my customers. What that means to me is that, as the owner of a townhouse with a predominiately northern exposure, I really don't have the best lighting to over winter tropical trees of my own. The Elms and (so far, I have found) the Bougs and also Pomegranates - allow me the option of pushing the trees into dormancy and holding them for at least part of the winter (I'm hoping to make it to the beginning of March) in a cool, dark place.
It's a careful dance. The trees need to stay out long enough for the shortened days and colder nights signal them to have a nap. I can even flirt with a light frost, if I have them up on the deck and not on the ground. But paying close attention - EVERY DAY- to what to expect that night is very important. I remember the morning I woke up to see the ground and my cymbidium orchids under a foot of snow. I didnt actually kill them, but it took a year for them to really recover.
I expect the bougs to actually drop their leaves outside- at which point into the slightly sheltered dark they will go. I'll start them off in the garage and when the cold really hits I'll move them to the coldest corner of the basement that I can find. I'm thinking of looking for an old fridge but I think if I buy and move a fridge into the basement for the purpose of wintering plants, Dan - a.k.a. the lucky guy who lives with me- will have far to much less than flattering dialogue to contribute (Something about the hydro bill. I dont usually listen).
The Elms won't drop their leaves outside, but when I bring them into the dark garage the leaves will exit stage left. And then I'll keep them in the cold without letting them freeze for as long as I can, until they decide enoughs enough and start pushing out new growth. Once they do that it's back into the light.
I realize that most people have bonsai trees because they actually want to see them and that's terrific, but if you are planning a long winter trip- dormancy is an option. (But you have to start NOW) It gives the trees a rest (and don't we all need a rest!). Black olives will also go dormant if they dont get the light and the heat that they require - and quite honestly it can be very difficult to keep them from nodding off- so don't freak out and think they're dead. Just set them aside and wait for the summer to push them back to activity.
Please note however that dormant trees need water! Not nearly so much actively growing trees, but check them once a week and try to keep them just barely moist - or damp, but never bone dry or you'll kill them.