Decades of Data
In January 2012, the United States Department of Agriculture (USDA) released an updated version of their Plant Hardiness Zone Map. Oregon State University’s PRISM Climate Group used sophisticated mapping technology and 30 years of meteorological data to create this new web-friendly version. First published in 1960 and updated in 1990, this map is designed to help gardeners and growers determine which plants will "winter over" in their hardiness zone.
Because heat is also an important factor in determining which plants will survive in a given region, the American Horticultural Society developed the Plant Heat Zone Map to provide guidelines for the other end of the temperature spectrum