Hello Everyone,
I live in North Dakota and as we get winters down to -35F (-37C) I have had to come up with a way to keep my trees alive. While some of these trees could survive if planted and established here, none will survive with their roots so exposed in pots. So, I have designed and built an enclosed, bottom heated, cold frame for the task. Below are some pictures showing the different layers of the design. I will be using a large water proof heating pad, an aluminum sheet for heat transfer and a sturdy floor, and a lot of styrofoam packing peanuts for insulation. Let me know what you think or if you want additional details.
Thanks
Spencer

Oh, and the heating pad won't be on constantly. I bought a thermostat with a temperature probe that I will put in one of the trees soil. The heating pad will come on if the soil gets below a certain temp.

That is not a cold frame...
Beautifully built though. Plan with the thermostat sounds good.

Quick update for you all. Its gotten cold here, already down to around 4F (-15C) will 3 snow storms. The cold storage trunk is working as designed. The thermostat prob in the soil and the heating pad are keeping the soil between 30 to 36F (-1 to 3 C). Here are some additional pictures.

Yes, my trees are mostly twigs, they are mostly new seedlings. Gotta start somewhere and I'm not letting the cold stop me.

I'm glad it is working!

The cold storage structure has been very useful this month. Below is the forecast for the next week. Gonna get down to -28 with a wind chill of -52F. That's -47C.