Then there's the Southern 6b. Definitely by the old- and even in some areas by the new- USDA zone map, there are areas of 6b in the South that have enormous magnolias, minors and needles in the wide open. Northwest Arkansas, Southern Kentucky, Northeast Tennessee and Western North Carolina come to mind.
Where the palm guru of Tennessee, Mr. Cole, has grown palms since before the 1960s (through the TN all-time record lows), is almost definitely located in 6b per the old zone map in Quebec, TN. Sabal minor has naturalized there for over 50 years and is found all over the area. He has enormous ancient needles.
Nashville- an old zone USDA 6b has some of the largest magnolias I have seen in my life- and I've been all over the South. Some are estimated to be pre-date the Civil War in the Nashville City Cemetery. I've shown some large live oaks as well. There are large cotton fields in Middle and West Tennessee in areas that were also rated 6b on the old zone map.
The only time I use the zone map now is when I mentally compare zones within a region. For example: Nashville vs Birmingham. Seattle vs Portland. Baltimore vs New York City. Boise vs Salt Lake City. The coast and mountains just skew reality too much in the world of flora and fauna.