USDA Growing Zones and Plant Hardiness

Posted by Jamie McIntosh Dec 30, 2008

After moving from Florida to the Midwest, denial was a powerful coping mechanism for the harsh winters here. We Midwesterners do many things to cope with the bitter cold that grips us for months at a time. Hot chocolate, high heating bills, and electric blankets come to mind. For the gardener, add houseplants and grow lights to the list. Regardless of what we do to get through winter, ignoring one’s USDA Growing Zone shouldn’t be one of the coping strategies.

The USDA plant hardiness map divides the United States and Canada into eleven main growing zones based on the lowest temperature that region experiences. Plant retailers in turn can mark their trees, shrubs, and perennials with the appropriate growing zone, allowing you to know if you will be greeted with sprightly green sprouts or brown mush in the spring.

Although I’ve lived in the area since 1994, I was beginning to doubt the accuracy of the USDA growing zone map. How dare they proclaim that I must suffer through temperatures plunging down to -15 degrees F? After one mild winter after another, I boldly proclaimed my zone as mild as a rating of “6,” and I planted and planned accordingly. This winter, howling 80 mph winds ushering in temperatures in the negative double digits have sadly proven the USDA’s plant hardiness map to be the useful gardening tool it always has been. Oh well, I needed an excuse to buy some new plants this spring.