They redid the plant hardiness zones a while back. Thou many feel it may have been more prudent to have waited. Climate change does not simply mean warmer more extreme weather. It can also include colder more vicious winters.

As far as most plants and roses are concerned there is not a lot of difference between 6b and 7a. Except for roses like teas and noisettes. One that may survive in 7a sooner or later will get zapped by a polar plunge that comes your way. As in what happened where Diane lives in Idaho. They were slammed last year with a harsher winter than normal. So most roses will be fine wether you are a six or a seven.

Patty- I agree. We generally have warmer winters now but still sometimes dip into the z5 minus 20 winter temps even though our agricultural zone has been changed to 6. It is also dependent on elevation and even population density. My mother lives at a lower elevation in a higher population town than I do ( we are very rural) We're about 3 miles from each other. She always gets less snow than us and warmer temps year round so I think it's best to observe your own environment and plan accordingly. One winter we had a really horrific ice storm that knocked out power for 5 days. I went to my mother's house to warm up. She was surprised we had no electricity and was wondering why they were cancelling school over rain. She had no idea that just 3 miles away towns were coated in a thick layer of ice.

Sharon

This isn't the USDA map, and seems to have some, um, interesting deviations in your part of the world. Going on nothing else, I'd follow the USDA map. If you run into some old-time locals, ask their opinion. When the new USDA map came out, most easterners felt changes were either insane or obvious.

Just a tidbit here, back in the late 80s thru the 90s we went thru a rather warm era if thats what you would call it. Anyway winters were not going below zero here. I've read about it but it is too complicated for me too explain.

Eventually they changed those zone maps and I got a bit complacent about my plantings. So that first winter where the below zero temps came back. I found myself outside trying to explain to the roses what was about to happen to them. Then giving the kids a bit of a pep talk on how they will become stronger for what they've endured. Geeze I hate winter.

I've been picking stuff for zone 5 to be on the safe side. I was thinking if this was true, I would get up to zone 6. lol I'm definitely not doing zone 7 anything, because I remember it getting super cold one winter in South Carolina.