let's be on the safe side and say 5

As far as Ohio goes, if you live either within 10 miles of Lake Erie, or in the Southern area of the state from Cincinnati to Marietta (along the Ohio River), you are probably safely zone 6. Since much of Ohio is zone 5b-- if you also live in a large metro area (in the 5b areas)....ex... Cleveland, Akron, Toledo, Columbus, you are probably also safe with some plants from zone 6. But for the most part if you live in a rural area or small town in the northern 75% of the state, you are probably safest planting for zone 5.

I live in downtown Columbus, and my rule of thumb is I sow seeds for zone 6, but buy plants hardy to zone 5. (I'm cheap that way.)

Good one Alison! I guess I do that too but I never really thought about it. Definitely 5 on the high priced perennials.

Im zone 6 all the way here in cincinnati.... though i must confess i try to trick mother nature sometimes by planting zone 7 plants in those elusive microclimates.
i have 50/50 success with those microclimate experiments

Sue
"The one thing all gardeners share in common is a belief in tomorrow"

Assuming from your name, you are in Akron? I live in Stark county, and I believe I'm zone 5. It can be a bit confusing with so many different maps.

Someone told me that here in Troy, I am zone 5. Dayton is the dividing line for zone 6. You can get micro climates here, and if you live IN town then you can do 6, but you are safe to zone 5.....

I know what you mean....radically confused I am! But after talking with some nursery folk here, I'm less confused. They said they only carry plants to zone 5 up here in Troy because they are safe....

An interesting note about one particular Cincinnati area; I just got back from the Zoo and judging by what has survived and grown over the past 6 years, it is a solid zone 7, maybe even a 7b!. The past 6 years have run the gauntlet in minimum lows from -19 to -25C at the airport, but obviously not the case for the neighborhood of Avondale.
Unfortunately my digital camera went dead about 10 minutes after I arrived so no photos, but I will be going back soon.
1.Buddleia davidii does not die back to the ground there. There are some that are blooming on old wood and are over 10ft already, plus they are naturalizing in parts.
2.Lagerstroemia 'Hopi' are blooming now! Plus most are in the 10-15ft. range, pretty tall for that particular cultivar. There is a 'Natchez' about 9ft. tall that is just starting to bloom.
3.Araucaria araucana has put on about 1ft. of new growth since last year and is now over 4ft. tall. **right behind it is what looks to be a Aracauria heterophylla, but could be an angustifolia (still a juvenile)that survived the winter with some serious damage but is flushing out new growth.
4.Albizia julibrissin is naturalizing all over the zoo.
5.Aucuba japonica and Fatsia japonica specimens both look outstanding and have put on nice growth.
IMO it is amazing to see many of those species thriving in one of Cincinnati's urban neighborhoods. IMO it is the urban heat island effect that creates such growth and naturalization.