The new USDA climate map and what it means for you
“Local news sources reported earlier this week that the United States Department of Agriculture has released updated climate maps based on data accumulated between 1976 and 2005,” explained Debra Hopkinson, former owner/partner of the DanDe Greenhouse here in Clinton, Tennessee. “What makes these maps so radically different from any previous ones is that they are the first to utilize the state-of-the-art technologies of personal computers, the internet, and interactive GIS that have been developed over the past 15-20 years. Designed for the worldwide web, these maps coupled with a broadband internet connection are interactive, and exceedingly more accurate than the last version published in 1990. Even if the only internet connection you have is dial-up, static images of this updated information is available by visiting the website and entering your local zipcode. Your local climate zone is displayed in half-mile segments, which, here in East Tennessee, where elevations can change drastically across short distances, makes these maps the most accurate ever produced. Visit http://planthardiness.ars.usda.gov/PHZMWeb/ and follow the instructions on the screen. Exactly how much this new data will effect any given garden or gardener in our area will depend a whole lot on the data that gardener has used in the past to determine the frost-free date in Spring. The older data and guidelines that we have used personally for the past 35 since we have been in East Tennessee always had to be adjusted depending on exactly where we were living in East Tennessee at the time. My husband lived over a period of several years at various elevation levels, initially, just across the state line in Waterville, North Carolina, and later in southwest Cocke County here in Tennessee. At the former address, his backyard was the Smoky Mountains National Park and across the street from his front yard was the Cherokee National Forest, at the foot of Mount Sterling, which means the elevation was upwards of 2000’, while at the latter address, was down in the neighborhood of 1300’. (By contrast, the elevation here in Clinton is 820’, yet it also varies from valley, hollow, to ridge-top.) The old frost-free data had to be adjusted for the differences in elevation; at the former address he determined the frost-free date to be around May 10th, while at the latter address he determined it to be a week or so earlier. Of course, the best data to determine frost-free date and first-frost date in Spring and Fall respectively is personal experience and personal garden records! And one must always remember that the data reflected on these government maps cannot predict accurately any rogue, late-Spring or Early-Fall, cold-weather snap that might produce a frost, therefore, it is always wise to plant a few days after the frost-free date in the Spring and a few days before the expected first-frost date in the Fall.”
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