I would think that a green house would be the way to go. A cheap one out of pvc and plastic.

If they are northern highbush varieties my guess is they would be ok if the winter is not too severe. My potted plants, all northern highbush have made it through 3 winters successfully and we hit zero several times last winter. . If you are still concerned, have several loads of sawdust brought in and bury the pots after they go dormant.

RM

My blue crops and elliotts overwintered fine in their wind protected site, with great snowcover. I'd be concerned with high winds and exposed pots below zero. Yes, I need a greenhouse, just in case.

Even "southern high bush" blueberries can take quite a bit of freezing temps, (some botanist are classifying blueberries into 2 types, lowbush, (exclusively a couple of northern species) and highbush. And like apples, some require more chill hours than others, but are the same species, (Vaccinium cyanococcus or Vaccinium corymbosum; Since these plants will readily cross pollinate, it will take a geneticist to really tell us what is what).

Therefore, I would not worry too much about them being able to over winter, just remember that just because the plant isn't actively growing doesn't mean that it doesn't require adequate watering.

I over wintered about 40 2 yr. old plants in pots, outdoors in NE Ohio last year, with no problem. I know of a garden center that keeps their potted blueberry plants in a greenhouse over winter. The owner/manager said that they have to water about the 1st of the year and had trouble with mice getting in the greenhouse and nibbleing on the plants. I'd maybe do as Riverman suggested and cover the pots with mulch, leaves, sawdust or something to help insulate.