The Plant Hardiness Zones are defined by the United States Department of Agriculture (USDA). The USDA map, which map is based on the average annual minimum winter temperatures, and is the generally accepted standard in the United States by gardeners, farmers, growers and sales of seeds and plants can determine which plants are most likely survive and be productive in an area.
USDA Agricultural Research Service (ARS) Hardiness Zone Map
Specific details regarding the map can be obtained on the USDA site at:
- Find Your Plant Hardiness Zone