After the earlier discussion around garage temps, I put a thermometer in my attached unheated garage. Overnight low outside of 5F, but it was 36F inside the garage. YMMV. I am always overwintering things I bought but didn’t get planted. I have eyes bigger than my stomach when it comes to plants and trees.

Although this is not an issue I have to deal with (thankfully), I learned back in my hort school days that the "sweet spot" temp range to overwinter cold sensitive plants is above freezing but below around 42F. This should negate potential cold damage to roots, potential foliage damage to any evergreens while maintaining adequate dormancy conditions and chill requirements.

I would try to create storage conditions as close to this sweet spot as possible. And be sure to keep pots/soil adequately hydrated.

Hey 'gg', I have been doing this for years. Sometimes I remember to do the "ken_adrian" hack ie putting snow or ice on the container but more often than not I do nothing until maybe March when it is still to iffy to bring the pots outdoors but some may be coming out of dormancy and could benefit from a bit of moisture.

After the earlier discussion around garage temps

I suspected there was another similar thread but I couldnt find it to add to it rather than create another.

I'm venturing a guess that my unheated attached garage is between 10-15 degrees (Fahrenheit) warmer than outside temps. At this house, I haul a few things into the pole barn over the winter. The barn is neither insulated nor heated, so it gets colder than the garage, but obviously the plants are protected from the harsh winter winds. Haven't lost a thing yet. I do put snow on the pots around end of January or so, the purpose being to slowly, gently water them during spring thaw (nothing to do with insulating them).

In our cold cellar the other day (attached to the house, below the front porch) (looks like about +6C/43F; at the time it was -15C/5F outside).

(Historically, I don't think I have seen it colder than 4C/39F)

The coldest I ever saw in my garage was about 23F. Outside, it was about the same, only with a minus sign in front of it. My house was built in the mid-60's, and I don't know how much insulation is between the house and the garage. Probably not a lot.

With my extreme winter temps that can occasionally dip to -40, the coldest the garage has become is -8 to -10 C / +14 F which has kept all but the most tender potted plants without troubles, even Japanese maples for the time that I had been maintaining a few of those.

Rouge, Air temp last night was -6F for me, and the garage is holding steady at 38F. We wont be out of the teens this week, with nights below zero as well, so it will be interesting to see if the garage holds steady.