No but old house gardens may stretch the truth a bit. And they are not alone in this. Steve in Baltimore County.

Overall, I don't think one dahlia variety is hardier than another (I'm sure there are exceptions). In your part of the country, I wouldn't chance leaving them in the ground. I agree with Steve on how some (many) catalogs stretch the truth as to hardiness. Does it mention that dahlias do not like wet feet? Here in the Pacific Northwest, more dahlias are lost in the winter to that than to freezing.

Teresa

Old post, but worth refreshing. I grow this in zone 6b and it has successfully overwintered for four years, no special protection.

it even looks good from the back.

Looks like you have it planted next to a driveway. Might have helped. It's awesome when dahlias come back... even better when the variety is of a good quality.

Folks who have successfully overwintered clumps in freezing zones seem to have certain things in common:
-soil is well-drained (raised above the normal water line), so moisture does not rot out clumps when they are dormant.
-clumps are close to a heat-collector, like siding on a house, driveway, etc

One thing folks wanting to attempt cold-climate overwintering can do is cover the cut-down stalks with a tarp in fall, and heap a foot or two of leaves or 6 inches of mulch on top. If you reverse that order, you might well find that your buried clump is now chewed out by a large family of well-fed mice that were nice and cozy with all that dry bedding you provided for them.

Cheers!
-CiCi

Yes, I have this one planted on both sides of my driveway which gets a lot of sun in the winter.