Plants vary in hardiness according to their genetic make up. The term hardiness usually refers to a plantís ability to survive the coldest winter temperatures likely to occur in a given area. The United States Department of Agriculture, the USDA, has developed a hardiness zone map for North America. You will notice that Kentucky falls within hardiness zone 6. Plants suited to this hardiness zone are able to tolerate winter temperatures down to about -10 or -15 degrees Fahrenheit. This is air temperature, not wind chills. Plants rated for a higher USDA hardiness zone, that is 7 or above, would likely show some winter damage when planted in Kentucky and might also fail to thrive in our climate. Plants rated for a lower USDA hardiness zone, say 5 or below, would survive Kentucky winters and for the most part should do fine in our climate. Most reputable garden centers and nurseries will only stock material suited for the local environment. However, one should be especially careful when ordering plant material from a nursery companyís catalog. The catalog may be meant for a wide area of the country and some to the material advertized may not be suitable for your specific growing area.
USDA Hardiness Zone Map