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: Hardiness plant classification according from 1 to 11 scale, varying on Earth, depending of coldest month (January) average minimum temperature. So, these zones correspond to following isothermal:
Z1; inf. à -45.5 °C
Z2; -45.5 °C
Z3; -40 °C
Z4; -34.4 °C
Z5; -29 °C
Z6; -23 °C
Z7; -17.7 °C
Z8; -12.2 °C
Z9; -6.6 °C
Z10; -1.2 °C
Z11; sup. à 4.4 °C