Thanks for the concern! (I love BNutters.)
Here's the story: I bought a Kiyo hime maple and a Rhode Island Red maple from Mark on FB auction in early December. He shipped them to me --extremely well packed, the bigger one double boxed -- and I put them in my uninsulated garage. We have an insulated garage also but that stays at 45°F, too warm for maintaining dormancy.
The temperatures got down to the teens last week so I put the maples in their shipping boxes with the tops open, and put seed sprouting heat mats underneath the boxes. I also put thermometers in each box. The garage stays about 5° warmer than outside, and the heat mats kept the maples around 28°F. So far, so good.
This week the really cold temps are rolling in. I took everything apart on a day when it was 30° and put the heat mats inside the boxes; put the maples on the heat mats, and filled in around the pots with styrofoam peanuts and bubble wrap.The current outside temp is 7°; the garage is 18° and inside the boxes the maples are 25°. So far, so good I think.
In a few days when the low temps will be around -12°, I will cover the boxes temporarily with bath towels and keep checking the thermometers.
Does this sound like a way to keep my maples safe? It's the best plan I could come up with. The rest of my bonsai have been sunk into the soil in my garden and surrounded with evergreen boughs, and are now covered with snow...but it was too late to do that with the maples.
I wasn't planning to buy the maples but they sure were pretty.
Suggestions welcome!