There isn't one. I've wasted countless hours analyzing all of the available maps and, until the revised USDA Hardiness Zone Map is released next year (hopefully), there is no reliable map available.

I have a whole section on my web site devoted to Hardiness Zone Maps (http://www.centralfloridagarden.com/topics/hardiness/overview.html), but for a quick idea of how all this impacts Florida, try the link below.

My guess - you are on the northern edge of Zone 10. The current USDA Hardiness Zone Map (it's 18 years old and desperately in need of an update) would have you on the southern edge of 9B, but all of the interim maps issued since 1990 show you in Zone 10. My other guess is that the next update of the USDA Hardiness Zone Map will be similar to the AHS and other interim maps and it will confirm you are in Zone 10.

Since I'm on a run with guessing - I'd also guess that you have the same problem I do. I live in Lithia, also on the edge between 9 & 10, which means I get lulled into thinking I live in the tropical paradise of Zone 10 until a killer frost barrels in from the North every two or three years. It's enough to make a person schizophrenic.

Here is a link that might be useful: Florida Hardiness Zone maps

One thing you have to realize with any zone map is that weather patterns can change for a season or for a cycle of a few years. Whether you believe in global warming as a pending disaster or just a current cycle, you can't ignore the recent changes in climate. If you live on the edge of a zone, it doesn't matter if you call it 9 or 10 (or any other name you want to use), you should be prepared to deal with extremes from both zones. Even if you are deep into z10, a bad year can bring a freeze or two.

Kate

I agree with Kate. And another thing to remember is that your yard is a microclimate all its own, too. Many things will impact what you can grow, besides a hard and fast rule of which Zone you're in.

For example, my last house had a very heavy covering of oak trees over the entire yard. I successfully grew things there that froze and died in my neighbor's yard, where there wasn't the same amount of covering. So sometimes, you can get away with things that aren't recommended for your Zone.

I think there's a lot of trial and error involved in every yard. Of course, if you try to grow Zone 4 plants in Zone 10, your chances of success are slim. But you can often grow Zone 9 plants in Zone 10, if your conditions are right.

I say use the Zone maps as a general guideline, paying close attention to your own microclimate (shade vs sun, sheltered areas next to house vs wide open spaces, etc), and be willing to do a bit of experimenting. Some things that aren't recommended for your zone might work for you, and some things that ARE might not.

Good luck!

Marcia

but 10a???

I wonder because I have two River Birches and I was told that they do well in Tampa, just east of us,but that they have a hard time out here, because we are no longer zone 9b, but zone 10a. I have heard this from two tree nursery owners, that we are not 9b but really 10a...

They look beautiful right now( I just put them in a couple of months ago), seem to be doing really well, but now I am worried, they don't do well "in Zone 10",according to books, fwiw.

teeka

Everybody is right. The nursery owners are right, St. Petersburg has got to be in Zone 10 (see below). But Kate and Marcia are also right, there are always exceptions, especially with the weather.

There was a great thread in this Forum a couple of weeks ago about whether St. Petersburg was in Zone 9 or 10 ("Pinellas County is not Zone 9!" - http://forums.gardenweb.com/forums/load/flgard/msg0718214924632.html). If you look at the following comparison of temperatures in St. Pete and Tampa, it sure looks like St. Petersburg has a far milder climate in the winter.

{{gwi:910794}}

But the graph also shows that you still get an occasional frost and maybe that's enough to keep the River Birch happy.

It's amazing the difference being directly on the water (the Gulf, in this case) makes. Warmer air over the water, and all, I guess. Thanks for that chart, bsewall. Makes St. Pete look like it's own big microclimate. (Is that an oxymoron?)

;o)
Marcia