Plantbot,

Philadlephia is in zone 6b. Tennessee, depending on where you are in that state, ranges from 6a to 7a - so yes, it could be similar.

I don't live in PA anymore, but my notes from a class at Longwood Garden say zone 7A. Longwood is about 50 due west of Center City. I gardened in the Philly suburbs, but worked in West Philly. Based on the plants that were grown in West Philly (and subsequently grown in my garden), I think zone 6 is a bit low. Try using a zip code to locate the "official" zone. One of the Center City zips is 19103.

I live about 15 minutes from Longwood Gardens and we are definitely in zone 6. I have never heard anyone from around here say zone 7A.

The problem with this designation is the "inner city" part. Even though Philly is right about on the border of 6/7 the conditions in any large urban area makes it seem a lot warmer than that. In such an area the frost line will be shallower and generally many more tender plants will survive even though out-of-zone. An example of this is that shrubs like Crepe myrtles are very hardy in the city but marginal in some suburbs, and fig trees are a common sight in many vacant lots and nearly never survive in the burbs.

As to the zone of Longwood, I've also lived 15 miles away from it for 40 years and its 7a in my books as I was told in a perennials class taken at Longwood in the early 70s

George

I say a solid 7a. Not quite cold enough anymore to be a 6. Maybe 6b. Kind of in the middle of 6b/7a.

I live in Philadelphia. Been here for 17 years now. If you plant zone 7/7a plants don't expect that they will survive without coddling. Even with coddling many will die. Buy and plant with that in mind.

George, do your 7a plants survive on their own?