About Plant Hardiness Zone Maps

Zone maps show ranges of average annual low temperatures over a period of years. Though absolute low temperatures are a principal indicator of a plant's winter survival chances, the duration of cold temperatures, daily high temperatures, wind exposure, soil moisture, soil temperature and amount of sunshine also play a role.

1990 USDA United States • Based on average annual minimum temperatures, 1974 to 1986 for the United States and Canada, and 1971 to 1984 for Mexico. (National Arboretum web site)

Prism Group • Contracted to produce the latest USDA Plant Hardiness Zone Map). 

2004 United States • USDA style map by Arborday based on average annual minimum temperatures, 1990 through 2004.

Georgia • Based on average annual minimum temperatures, 1970 through 1999. Compiled by SPS member Tom McClendon of St Marys, Georgia.

North Carolina • Based on average annual minimum temperatures, 1940 through 1999. Compiled by SPS member Bob Snyder of Winston-Salem, North Carolina.

Tennessee • Based on average annual minimum temperatures, 1970 through 1999, includes temperatures for active weather stations in Tennessee and bordering stations in surrounding states. Compiled by SPS member Jeff Stevens of Apison, Tennessee. This large file may be slow to load. Click here for the PDF version.

Australia Zone Map

British Isles Zone Map • Based on average annual minimum temperatures, 1961 to 2000 for the United Kingdom and Republic of Ireland, including the Channel Islands and Normandy.

Canada Zone Map

China Zone Map

Europe Zone Map

Europe Zone Map (GardenWeb)

“The New USDA Plant Hardiness Zone Map” by Peter Del Tredici in Arnoldia, Vol. 50, No. 3, contains reproductions of plant hardiness zone maps from:

• Alfred Rehder’s Manual of Cultivated Trees and Shrubs (first edition, 1927)

• Alfred Rehder’s Manual of Cultivated Trees and Shrubs (second edition, 1940)

• USDA (1960)

• Arnold Arboretum (1967)

"Plant Hardiness Zone Maps," by Donald Wyman and Harrison L. Flint, in Arnoldia, Vol. 27, No. 6, contains the Arnold Arboretum's 1967 map in color.