They wouldn't survive winter in Zone 5. You could keep them indoors for the duration but do prepared that they will look scraggly. They do need sunlight so a shed with no heat and no light isn't a good area. That sort of treatment is for plants that can grow from corms or bulbs and stay dormant during winter. While indoors, water sparingly. Water so that the soil is moist but not overwhelmingly damp. water only when the soil goes dry.

PS I like your sense of gardening. It's how I started enjoying my English Cottage garden. In my case, I prefer to use broken pottery for garden decors. Re the brick wheel you made, I suggest surrounding it with thyme spilling out of the gaps.

Actually I live in zone 5a and have grew mums outdoors in my garden for many years.
I planted one a couple years ago that came from the florist shop and it is still surviving but just starting to get buds now which I think was caused because I moved it this year to another spot in my garden.

I have 3 that wintered over the past 2 years. I just thru leaves over it and they lasted .The sales person told me they wouldnt. They get bigger and better each year.

I have better luck with the ones I plant in the spring, but I've almost always gotten at least one extra season out of my fall mums.

I would plant them now, and just let them bloom in their new home. The will also put out some new roots. Once they have finished blooming, let them grow for a while. I would mulch them only after the first freeze - November? December?. The mulch helps to prevent the heaving that causes the loss of many plants.

The best place is in a sunny, well drained location, NOT crammed into a space that has lots of plant material to shade it, eg under existing shrubs.

Oh, and to encourage great blooms, don't forget to cut them back in Mid June and mid July.

Hope this helps. I'm currently about to enjoy mums planted over the last 6 years.

I have a former potted mum that I planted 6 years ago. I do nothing to it, other than pruning. It gets flowers every year.

Some are hardy, some aren't. They should be labelled, but even if they aren't, it is worth a try to see if one you like will survive.

Well some mums seems to be survivors. I'll double back on what I said and say give it a try. But mulch it well. In specific zones, there are microclimates which keeps that plant warmer. What is zone 5 in one area isn't the same as the zone 5 in another area. It's meant as a general guide. The mums will need to be dugged in soil and topped with good mulching. It should also be located in a protected area like near a wall where winds and winters heaves and thaws don't ravage them. This is simply what's termed as zonal denial. (Like in Vancouver they are planting bananas & palm trees)

Good luck.