Q.Trees in pots
I have two small blue spruce trees (18″ high) planted in large pots, which have been outside framing the front door(faces southwest) since spring. Will I need to winter these inside or in an unheated garage or what would be the best choice? Some winters we can get as cold as -20.
You will not need to winter the trees inside.
The are winter hardy to zone 3.
Continue to water the trees into the dormancy and add a small amount of water a few times throughout the winter.
https://www.gardeningknowhow.com/ornamental/trees/colorado-blue-spruce/care-for-colorado-spruce.htm