Georgia Garden Girl

Zone 8 is my USDA plant hardiness zone.  The United States Department of Agriculture defines zones by average annual minimum temperature.  According to the USDA, the USDA plant hardiness zone map “is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location.”  Zone 8 cuts a wide swath across the southeast, extending from coastal North Carolina all the way to Texas.  Because the USDA’s zones are based on average minimum temperatures, they are helpful for determining which plants may survive the winter in your garden.  The USDA zones are also a good quick indicator for determining whether your area has enough cold days for plants with “chill hour” requirements to thrive.

Another useful standard is the American Horticultural Society’s Heat-Zone Map, which defines zones by the number of “heat days” (temperatures over 86° F) per year.  My garden is in Zone 8 according to the AHS’s Heat-Zone Map.

Almost every garden book, catalog, and magazine contains a USDA plant hardiness zone range for each plant.  The AHS heat-zone standard is much newer than the USDA’s standard, so you may not find a heat zone categorization on every plant, but it is becoming more common.

What does all of this mean?  Well, it’s pretty simple.  Look at the zone range for the plant you’re interested in buying.  If your garden is within that zone range, the plant will probably survive in your area.  You still need to consider other important factors like light requirements, type of soil, amount of water required, how big the plant will get, when the plant flowers, etc.  But at least the plant will be in the right zone.  If your garden is not within the plant’s zone range, you might think twice about that plant.  For example, I think lilacs are lovely, but many lilacs require cooler weather than we have in Zone 8 and are coded for Zones 3-7.  Instead of trying to grow a variety of lilac where it probably won’t thrive, I’d be better off looking for a variety that is more heat tolerant.  Another example: I would really like to have a lemon tree.  According to the plant catalogs, however, the plant hardiness zone range for a lemon tree is Zone 9-10.  So, I could buy the lemon tree, but I’d be on notice that the tree might not survive the winter unless I took precautions like keeping it potted and bringing it inside whenever there is a threat of frost.