USDA Plant Hardiness Zone Map
The 2012 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. The map is based on the average annual minimum winter temperature, divided into 10-degree F zones.
See link to find your zone by zipcode
http://planthardiness.ars.usda.gov/PHZMWeb/
Interesting Article @ The Dirt
http://dirt.asla.org/2012/03/06/new-...reating-north/
'Plants are retreating North'
Earlier this year, the U.S. Department of Agriculture (USDA) finally listened to what landscape architects, researchers, and gardeners have been saying for some time: plant hardiness zones are retreating north across the country. While the USDA argues that its new plant hardiness map, the first update since 1990, doesn’t show a clear connection with climate change, some experts disagree.