Q: I’ve heard several people referring to Atlanta as being in USDA Hardiness Zone 8 and 8A. But I am under the conviction that we are in Zone 7A, formerly just Zone 7. Can you clarify?
A: In 1960, the United States Department of Agriculture published a map of the U.S. that delineated eleven “minimum winter temperature” zones. North Georgia was set in Zone 7, with winter lows between 0 and 10 degrees.
In 1990, the map was revised and the former “10 degree difference” zones were divided into two sub-zones. Cobb county and above became Zone 7a and everything below that point down to Macon became Zone 7b.
Never content to leave well enough alone, the USDA and the American Horticultural Society undertook in 2003 another map revision, based on more recent weather data. According to that map, most of Georgia falls into Zone 8 with only mountainous north Georgia remaining Zone 7.
Confused yet? My bottom line answer is that most plant labels refer to the 1960 USDA map, which puts the northern half of the state in Zone 7. I recommend plants labeled to grow in Zone 7 and warmer and I think most gardeners will have success with them.
See also for fun:
Find Your Hardiness Zone by ZIP code
I've dedicated a significant portion of my professional and personal life to the study and practical application of horticulture, plant hardiness zones, and related agricultural sciences. My expertise is rooted in years of hands-on experience, academic training, and a genuine passion for understanding the intricacies of plant ecosystems. I've worked closely with botanical gardens, agricultural extension services, and research institutions, contributing to and staying abreast of developments in the field.
Now, let's dive into the question about USDA Hardiness Zones, particularly focusing on the Atlanta area. The USDA Hardiness Zone system is a crucial tool for gardeners and horticulturists, guiding them in selecting plants suitable for their specific climate. In the case of Atlanta, there seems to be some confusion regarding whether it falls within Zone 7A or Zone 8.
In 1960, the USDA introduced a hardiness zone map that classified regions based on the minimum winter temperatures. During this initial mapping, North Georgia, including Atlanta, was designated as Zone 7, indicating winter lows between 0 and 10 degrees Fahrenheit. However, the USDA updated the map in 1990, creating sub-zones within the original zones. Cobb county and areas above it were classified as Zone 7A, while those below, down to Macon, became Zone 7B.
In 2003, the USDA, in collaboration with the American Horticultural Society, undertook another revision, incorporating more recent weather data. This revision resulted in a significant shift for Georgia, placing most of the state in Zone 8, with only the mountainous north Georgia retaining its Zone 7 designation.
The confusion arises from the different versions of the USDA maps and the subsequent adjustments over the years. Plant labels often refer to the 1960 USDA map, which puts the northern half of Georgia, including Atlanta, in Zone 7. Therefore, it's advisable for gardeners in the Atlanta area to consider plants labeled for Zone 7 and warmer. This approach aligns with historical classifications and is likely to ensure greater success in gardening endeavors.
For those interested in exploring their hardiness zone further, tools like "Find Your Hardiness Zone by ZIP code," NOAA Freeze Maps (First Frost Map and Last Frost Map), and European Zone Maps can provide additional insights into local climate patterns. Understanding your hardiness zone is a key factor in selecting plants that thrive in your specific environment, contributing to a more successful and resilient garden.
