Dianthus caryophyllus tends to be hardy in zone 3 in my experience, but never flourishes, and diminishes from year to year. Fortunately, there are many other dianthus that do very well, though. Also, there is a hybrid dianthus called 'Mrs. Sinkins' that I'd highly recommend as an excellent substitute for "real" carnations - it's hardy and vigorous, has blue foliage and is very heavily spice-scented, with white flowers.

By the way, a lot of zone 3 gardeners from the prairies hang out at the Far North forum - come on over...