Asking a fellow gardener their zone is a quick way to find out what you may have in common with them, for it indicates if they are likely to grow the same plants that you do. Then the conversation can really begin.
So, when I recently heard that a new USDA Plant Hardiness Zone Map had been developed, I wondered if I would have some kind of identity crisis when I looked at it. Would I suddenly find myself in a new gardening zone?
The new map is different (and somewhat harder to read, in my opinion) than the previous map, which had been in use since 1990. However, it seems more accurate in that it shows more details, including more clearly defined areas that are affected by changes in elevation.
The new map was created using temperature data from 1976 to 2005. Data was collected from more weather stations than before (nearly 8,000 of them), making it more accurate. In recent years, the technology to measure weather has improved dramatically, and this has resulted in a more precise map. I understand that the new map even takes into consideration factors such as proximity to large bodies of water, prevailing winds and land topography.
The map is divided into zones based on the average annual minimum temperature. The new map shows 13 zones in the United States (the old map had 11). Each zone represents a temperature range of 10 degrees. As with the old map, each zone is further subdivided into “a” and “b” categories, which represent a five-degree range. The lower the number, the colder the zone; and “a” is colder than “b.”
The 1990 map showed five different zones for Georgia (6b through 8b). The new map shows seven (6a through 9a), meaning that one colder zone has been added to the state, as has one warmer zone.
The difficulty I have in reading the new map stems from the subtle shading differences between zones (the old map had more clearly defined boundaries). Fortunately, if you can’t quite tell which zone you’re in when you look at a printed map, you can go to the USDA website: www.planthardiness.ars.usda.gov. Type in your zip code, and it will tell you exactly which zone you’re in.
On the website there is also an “interactive” version of the map that allows you to zoom in and out to see zone boundaries at a much more detailed level. You can also view a static (non-interactive) version of each state’s individual map.
On the USDA website, I learned that my garden in Woodstock is now considered Zone 7b (with an average minimum temperature of 5 to 10 degrees), whereas before it was 7a (average minimum temperature of 0 to 5 degrees).
Now excuse me while I have a minor gardening identity crisis ...
Information about Extension Solutions for Homes and Gardens can be found on the University of Georgia Cooperative Extension website at www.caes.uga.edu/extension/cherokee or by contacting the Cherokee County Extension Office at 100 North St., Suite G21 in Canton at (770) 479-0418. The Georgia Extension Master Gardener Program is a volunteer training program offered through county offices of the University of Georgia Cooperative Extension.