The best way to store them is to dig holes somewhere in the garden and sink the pots into the holes = heel them in. If that is too cumbersome - and at 24" diameter, I understand the issue - then you need to store the pots somewhere quite cold but above freezing. The basement sounds too warm.......right around 35-40F is preferred. Maybe in the unheated barn if you can find a way to protect the pots from colder temps.

I think i‘ll put them in the barn. what about weapping them in a quilt to help keep them a little warmer when it’s super cold at night? it can get down to 0 or less from time to time.

0F is too cold. You must keep the ambient temp above freezing if left in the barn. Making a corral with bales of straw, wrapping the pot with bubble wrap or using a heat lamp on the coldest nights could help.

Obviously, GG is the expert so I am sure has some good reason for thinking otherwise.

There is a vast difference in overwintering a potted plant in a zone 7b compared to a zone 5 so not sure it is reasonable to make comparisons.

The roots of any plant are its most cold vulnerable aspect. And in a container, this vulnerability is at the forefront due to exposure to much colder ambient air than it would experience in the ground. While the "2 zone hardier" rule of thumb can work much of the time, it is not a hard and fast guarantee. Japanese maples are considered hardy to at least zone 5, some even to zone 4, but exposure of the root system to temps below 24F - which can even happen in my mild winter climate - for more than a few hours can kill them!

One always wants to protect the roots of containerized plants from any extended freezing. If planted in the ground, the roots are insulated by the soil mass surrounding them, so far less of a concern. In a container, they lack that insulation and one either needs to modify the temperatures they are exposed to or provide sufficient insulation.

I am from Texas, 2 hours NE of Houston and not nearly as cold as you all but last year we got down to 2 degrees.......unheard of for us - and I lost all but one of my potted clems. Wish now I had taken them into the greenhouse but we lost power for 4 days and at that point, was trying to keep myself from freezing to death. A suggestion I might make from what I do with my potted roses is that I have bought rolls of silver insulation - its easy to cut and tape & is about 2 feet wide and not that thick. You could do that and also cut and wrap those pipe insulators that look sort of like pool noodles around the pot and tape. Do those first and tape, then wrap the whole thing in the insulation wrap, put them in the middle of hay bales with insulation on top. There may be some sort of heat tape - check with a plumbing supply company about options. Good luck!

Judith