Follow Michael's and Susan's advice and it should be fine. I keep my rose tree in my shed for the winter and in the spring when things start to warm up I can tell when it looks like it wants to start budding out. That's when I wheel it back outside into the light. If there is going to be a deep freeze I wheel it back in. That's when the wheeled pot trolley is the most beneficial. It makes it much easier to move that big, heavy, tall awkward pot in and out. I've been doing this for 6 years now and it's still doing great!

Keep your tree quiescent - as cold as you can w/o exposing it to temps more than a couple of degrees below freezing, for as long as you can. There is no advantage in having them in leaf earlier than (mulberry) trees in the landscape. They are going to leaf out too early anyway, by virtue of the fact that soil temperatures warm sooner in pots than the earth warms in spring. You can't avoid that w/o refrigerating them, and who does THAT? Soil temperature is the stimulus behind the initiation of the spring growth flush. Al

No kidding! Hobby, it's frustrating. My weather has been just nuts..I had to bring them in for a week after having them outside for a week a couple of weeks ago..It was warmer then than now. So, they have all leafed out and now I have to bring them back in for next week because I am suppose to get snow and way below temps..Can't win! Bahama, you are SO lucky!

I'm not sure I'd be quite as cavalier about the potential cold damage as the above poster :-) Many trees - JM's in particular - are extremely vulnerable to cold temperatures with their root systems. And that increases when these plants are potted or held in containers, as there is no soil mass surrounding them to provide insulation. That's why it is suggested that containerized plants be hardy to at least 2 zones lower than yours if to remain outdoors in containers all winter long. Generally the trigger temp is 25 degrees.......below that for any length of time (like overnight) and you DO run the risk of freezing the roots and fatally damaging the plants. Most bonsai sites will confirm this as winter cold is a serious concern with bonsai enthusiasts. Other maple species may be hardier and will tolerate colder temps, however I'd not be inclined to tempt fate and so I would provide winter protection. As long as your unheated garage remains above the mid to low 20's, that should be fine. And you can bring in with leaves still on or not - the trees are already entering dormancy and any remaining leaves will be dropping shortly. Light is not a concern during ths period but cold and water are. If you can keep the temps between around 45F to 25F you should be fine and do not allow the soil to dry out completely but also do not over wet. Soil should remain just damp. FWIW, leaving containerized trees outdoors all winter without protection is usually reserved only for warmer zones - z8 and above. And even in these mild winter zones, care must be taken should an unexpected cold snap result in a significant temperature drop.