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Hardiness Zones

The hardiness zones of plants refer to geologically-defined areas where plants, or categories of plants, are capable of growing. These zones are determined by climate, with the major factor simply being the temperature. These zones have been adopted around the world, but were originally developed by the United States Department of Agriculture (USDA). When reading information about plants, it is normally referred to simply by 'zone'.

 

Simple Scale

Plant Hardiness Zones

Detailed Scale

0
a < -53.9
b -51.1 -53.9
1
a -48.3 -51.1
b -45.6 -53.9
2
a -42.8 -45.6
b -40 -42.8
3
a -37.2 -40
b -34.4 -37.2
4
a -31.7 -34.4
b -28.9 -31.7
5
a -26.1 -28.9
b -23.3 -26.1
6
a -20.6 -23.3
b -17.8 -20.6
7
a -15 -17.8
b -12.2 -15
8
a -9.4 -12.2
b -6.7 -9.4
9
a -3.9 -6.7
b -1.1 -3.9
10
a +1.7 -1.1
b +1.7 +4.4
11
a +4.4 +7.2
b +7.2 +10
12
a +10 +12.8
b > +12.8