Blake, as someone who lives in your area and grows a lot of maples in containers, maybe my experience will be helpful to you. Late winter/early spring weather in the Puget Sound area can be very unpredictable - mild and balmy one day with freezing temps and snow the next. That said, I repot maples pretty much year round......it just depends on the reasons and when I've purchased them. A routine maintenance repotting (and one that may involve root pruning) I generally reserve for just before bud break, although I've done it in late fall as well. Hard to say exactly when that may be, as it seems to vary both with weather and the tree in question. After examining the repotting candidates for this year recently, I'd guess I'd start this process in about 2-3 weeks or mid to late March - the buds on my trees are looking very good and healthy and starting to show signs of coming to life. These also tend to be some of my larger maples, so working with the plant while it is still pretty much dormant is both easier on me and on the tree. But it is quite possible to repot JM's succcessfully when in leaf as long as they are small enough to handle easily and you can provide some additional specialized care to get them over the transplant hurdle. I also don't pay too much attention to soil temps at this time -- that doesn't seem to have too much bearing on container soils, as they don't hold the moisture as avidly as Puget Sound inground soils do and they do tend to warm sooner as well. FWIW, I wouldn't necessarily consider planting a new JM in the ground at this time of year as the soil is simply too wet, in fact it's too wet to plant much of anything and you can damage the soil if you attempt to work it in this condition. I also don't provide any special winter attention unless it is a very small plant - 2G or less. Mine are out there year round and have gone through some seriously cold temps without any problems. They are in pretty good sized pots, however - repotting is a lot of work and I tend to use larger containers (15G at least) just because they seem to fit the scale of the plant better and don't require repotting attention quite so often. I addition to the excellent and helpful information you find here, you might want to visit the Maples forum too. There are a number of us that grow JM's in containers that post there regularly and lots of good info about growing these trees, both in containers and in ground.

Mona, I think in Manitoba a Japanese maple (planted in the ground) will always remain a small shrub. I just don't see it getting that large to be able to provide shade. First, they are slow growing, second, any part of the plant not winter protected will die back. One hardier substitute might be the Korean Maple (acer pseudosieboldianum) but even then it's slow growing and multi-trunked, it could one day be similar in size to a large lilac than a tree. Back to the topic of winter protection, I revised my winter protection method this year. Previously I surrounded the small 2-foot high Japanese Maple with a cardboard box (flaps cut off) and filled in and around the plant with peat moss and leaves. This worked very well, but was time consuming. Plus, the novelty of winter protecting things wore off. This year I mulched the base of the tree with a few inches of peat moss. After it snowed I wrapped quilt batting around the plant (secured with twine) and shoveled snow around the base of the small tree, maybe a foot deep. I then placed a thick plastic garbage can over the plant sort of pushing it into the snow that surrounded the tree. Once we had more snow I piled mounds of it around the garbage can in a drift. The Japanese maple survived winter with some tip kill to the branches but otherwise fine. Another advantage may be that I have my maple on the north side of the house near the foundation, which might be a sheltered spot as well as getting no sun in winter (the sun might prematurely heat things up and make the tree break dormancy in spring). When we often grow out of zone plants we often think of situating them in the warmest micro-climate in the yard, but I think sometimes that's not a great idea. You want a sheltered spot with dependable snow cover that doesn't melt halfway through winter. Glen

Depends :-) J. maples need at least 1000 hours of temps below 40F (~4.5C). Can it get that outdoors before it gets too cold? Or will it receive any additional requirements in the sunroom (heated? average winter temp?)? Temperatures much above the 40F mark will encourage the plant to break dormancy. And while these can go through an extended period without full or sustained dormancy occuring (lack of adequate chill hours), it is usually a short term situation at best. "Species that have well developed dormancy needs cannot be tricked out of them. If you attempt to give a such as species, for instance Japanese maple, Acer palmatum, an eternal summer by bringing it in the house, it will grow continuously for as long as two years. After a maximum period of sustained growth, a temperate climate plant will automatically go dormant no matter what the season or condition. Deciduous plants will lose their leaves, evergreens will curtail all new growth. This is very stressful to the plant and usually fatal. It will be 100% fatal if the plant does not receive the necessary period of cold temperatures required to break the dormancy."

Acer palmatum (and other Asian species of maple) prefer acidic soils, as do the vast majority of other plant types. They will tolerate somewhat alkaline soils as long as not excessively so (above 7.5, forget it) but will not necessarily thrive as they would in a more ideal soil condition. And are also subject to chlorosis under these conditions and leaf tip burn from accumulated salts - areas with alkaline soils generally have alkaline irrigation water as well and these trees do NOT appreciate that combo at all!! And regardless of soil chemistry, good drainage is a must.