i've heard some good sounding ideas about how to winterize bonsai. but now my questions is WHEN do you winterize them? i understand the basics i think. keeping the root ball from freezing and keeping the tree away from the drying winds. but when should you shelter your tree away? what temps should you look for? currently in my location the night time lows are around 42 and the highs are in the 50's. the regular trees still have there leaves on them and haven't all changed yet. we have only had one frost so far. as long as the night's haven't been dipping into the 30's yet i haven't sheltered my tree's. so i was wondering when i should. also i was wondering since winters are eratic around here. when the weather does climb into the 40's as it does periodically. should i move the tree's out of the shelter (igloo cooler) and let them get a little light or is it once they're in there they stay in there for the whole winter?