Probably a lot depends on how bad the winter is and where exactly they are planted. Even around here I've heard of people overwintering them, usually when they're planted up close to a foundation or south facing wall. You might have a pretty good chance! Older varieties might be hardier, they seem more solid and go dormant more than some of the newer hybrids which try to keep growing all year.

Hi Guys, I overwintered a small variety the year before and our winter was awful, that was was close to a fence tho. I also have some Crinum planted out but a few species are hardier. I was really nervous about planting them in the middle of the yard but I ran out of room EVERYWHERE else for plants, it was mid march and I needed to put them somewhere so they'd bloom. The flowers were much larger in the ground and they were beautiful! I dug around the 'Apple Blossom' bulb and it's the size of a softball, they really do well in the ground! My zone RARELY gets down to the cold of Zone 5, (the low it states is -20f, I have never had a -20f winter. It barely gets below zero and if it does it's not for an extended period of time. I wasn't really hopeful where I planted them for them to come back so I didn't really mulch too much, I just wanted to see the blooms in the ground and I did, I was satisfied.

For 20 years I have left my dahlias in the ground over winter. Normally, I do not loose more then 5 or 6. THis winter, I lost 100 out of my 130. I can not remember exactly what the weather was, except that it was quite cold for a couple of weeks from mid December. In November I was laid up for a month with Bronchial pnuemonia and had my foot in a walking cast. NO way I could have dug dahlias, but also, no way to predict that this would be the winter that killed my dahlias. We started out with a long warm fall that suddenly switched over to being really cold and staying frozen for about 2 weeks. I am only about 600 feet above sea level but on a shallow north facing slope. THe plants at the bottom of the garden never got even a ray of sun at that time of year. All my survivers were in the upper half of the garden and appeared to be quite random as to which survived and which did not. Totally unpredictable. I think I will at least dig and save out a tuber of my favorite ones, then perhaps bury and mulch the rest. I was heart broken this year to think I had lost Hillcrest Kismet, and all the mail order places were already sold out of it, but a couple of tubers looked like they might possibly have eyes. I lucked out have two live sprouts coming up. WHewww! Even Swan Island lost a number of cultivers to these early freezes this year, before all their tubers were dug.

Thanks everyone for your suggestions. There just wasn't a ton of stuff online about overwintering plants. Just "dig up your dahlias and put them in the garage for the winter" articles. Which is what prompted the question. To give a bit more information, I'm in Portland, OR, 7b(ish, it's been changing) and the plants came from Lowe's and their end of the season plant extravaganza. Normally, when I pay full price for plants, it's for sure a perennial that can take a good freeze or so. But...this stuff was too good to pass up. So, it's an experiment! I figure I'll cut back hard and mulch heavy with both wood chips and leaves. We'll see which ones are in good spots and which ones aren't. And, I'd like for all of them to make it, but maybe, maybe not. I do know that it's more too much water than too cold is what does tender plants in during the winter.