The plant hardiness zones divide the United States and Canada into 11 areas based on a 10 degree Fahrenheit difference in the average annual minimum temperature. (The United States falls within zones 2 through 10.)
Suggested hardiness zones are included for each item in this catalog. For example, a plant’s range listed at 4–9 means the plant is known to be hardy in zones 4, 5, 6, 7, 8, and 9.
Keep in mind that local variations such as moisture, soil, winds, and other conditions might affect the viability of individual plants. Urban areas and regions with bodies of water or mountains may contain climatic pockets that mirror warmer or cooler zones than the surrounding region. If it looks on the map like you should be in a different hardiness zone than the one we provide for you, you’re likely in a microclimate too small to represent on the map.