Zone 1: below -50 degrees 
                         Zone 3: -40 to -30 degrees 
                         Zone 4: -30 to -20 degrees 
                         Zone 5: -20 to -10 degrees 
                         Zone 6: -10 to 0 degrees 
                         Zone 7: 0 to 10 degrees 
                         Zone 8: 10 to 20 degrees 
                         Zone 9: 20 to 30 degrees 
                         Zone 10: 30 to 40 degrees

     for more detailed information:  http://www.growit.com/ZONES/index.htm