|U.S. Zone Map|
The U.S. Department of Agriculture first published the zone map in 1960. Based on a plants resilience and a zones climate the formulation is not without flaws. The ever changing weather conditions have required several revisions, most recently just this year. Still, it is a handy guide to comparing climates and determining what might be the most appropriate time to begin planting. Example: I live in the heart of heat and drought where Spring gardening is earlier than other regions. The winters are also milder which tends to extend the duration of fall gardening.