m5eaygeoff wrote:  It is not cold in the UK at the moment, unless you are in the north of Scotland.

UK?? Ithink op is in USA or one of the other 4 countries that use the imperial system.

I live in Maryland, USA. The USDA plant hardiness level is 7. It has been cold lately, but it is predicted to be about 14°C today and 18°C tomorrow before it drops back down to about 7°C, and bounces between that and 12°C. How would I acclimate it gradually to tolerate the outdoor environment? 

Leave it outside unless it gets cold. 7C is higher than it is here all day, and mine are where they have always been outside. As I said before if it is going to be below freezing then put it in a shed overnight, under a bench or table will also give it some protection

Protection from what? The wind? I know wind can be an issue, but the temperature would still be cold, wouldn't it? 

yes but it would not be quite so low as out in the open. Once again, unless the temperature gets well below freezing the plant will be fine.

Like -5°C? That is the coldest it is predicted to be in the foreseeable future. It occurs at night. I forgot to look at the lows when I described the temperatures earlier. 

If it was going to that low I would put it in a shed or garage, but not until it is does.

So, to summarize, the bonsai will be fine outside as long as it is above 0°C? If it is below that, I should move it to a shed or garage for the night? Would that be warm enough? Would about "heeling-in"? 

The coldest period my chinese elm has gone throe was 6 weeks of temperatures below -10, day as night. The lowest recorded temperature during that spell was -18. It did fine. However that tree had been outside the whole transformation from summer to winter and where strong and prepared. When you have a weak tree indoors all the way to mid december, it is not prepared. That is why I recommended 5c. Cold enough to go dormant and above freezing. If you cannot provide that conditions, Geoff suggestion may work. But it is slightly more risky.

Then what should I do when it gets too cold? Would a shed or garage keep it warm enough? Are there any other methods? What about "heeling-in"?