I'd do my best to get them in the ground, water them in well, and mulch around them. Unless you have a greenhouse or some place with sun that won't freeze, then you could cut them back, keep them moist but watch out for root rot, and they will likely survive.

The nurseries around here have late September sales where stuff is 70% off, and we've often stocked up. I've done both - planted out in mid-October and kept them going in a greenhouse. Better results with planting them out. A lot of times they've been over-watered all summer long at the nursery and the plants are root-bound and water logged. For inside, its best to repot them in a larger pot, outside sort of untangle the roots to spread them out and then plant.

You can always plant them out in some spot then dig them up and replant them in the spring.

Lynn,

I did the same thing last fall. I picked up some clearance perennials cheap in November. It was getting cold and digging was becoming difficult. I ended up sinking them in the raised veggie beds and covering the pots completely with soil. I watered them in well, mulched them and they came through the winter fine. In spring I was able to plant them out and they're doing well.

I would suggest slipping them out of the pots and check the root systems first. If they are pot bound, I'd leave the pots off before putting them in soil. I think having the roots touching cold plastic all winter wouldn't be good. The only reason I left pots on some was I planted them very close together and was afraid I'd damage the roots when I dug them up. In retrospect, I'd have left the pots off.

If you don't have veggie beds, just pick a spot where the soil is workable and dig a trench big enough to hold them and plant them there for the winter. Then you can plan where to put them in spring. Do take notes on which plant is which, or leave the plant tags with the plant. It's hard to tell what they are in early spring, before they get growing. I hope this helps.

Barb