Gardening in the dry, semi-arid subtropical region of Southwestern U.S., USDA Plant Hardiness Zones ranging from 3b in Colorado, through 11a in the coastal regions of California.
The USDA zones map is a useful system for determining what plants will survive and grow in certain areas of the Southwestern U.S.
Understanding how these hardiness zones work means you can choose the right planting time, and optimize growing for your climate.
States in USDA Southwestern U.S. Map
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Arizona
Arizona has a wide variety of localized climate conditions, due to its large variations in elevation. The USDA Plant Hardiness Zone classification ranges from 4b, to 10 near Yuma.
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California
Most of California has a Mediterranean climate, also due to the state’s large size the climate ranges from polar to subtropical. The USDA Plant Hardiness Zone classification ranges from 5a, to 11a near Los Angeles.
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Colorado
The climate of Colorado is more complex than states outside of the Mountain States region. The USDA Plant Hardiness Zone classification ranges from 3a, to 7a near Durango.
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Nevada
Nevada is the driest state in the United States and made up of mostly desert and semi-arid climate regions. The USDA Plant Hardiness Zone classification ranges from 4a, to 10a near Las Vegas.
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New Mexico
New Mexico has long been reputable for its pleasant, temperate climate. The USDA Plant Hardiness Zone classification ranges from 4b, to 9a near Deming.
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Utah
Utah features a dry, semi-arid to desert climate with the mountains feature a large variety of climates. The USDA Plant Hardiness Zone classification ranges from 4a near Salt Lake City, to 9a in the southern parts of the state.
Zones in USDASouthwestern U.S. Map
3b (-35 to -30 °F/-37.2 to -34.4 °C)
4a (-30 to -25 °F/-34.4 to -31.7 °C)
4b (-25 to -20 °F/-31.7 to -28.9 °C)
5a (-20 to -15 °F/-28.9 to -26.1 °C)
5b (-15 to -10 °F/-26.1 to -23.3 °C)
6a (-10 to -5 °F/-23.3 to -20.6 °C)
6b (-5 to 0 °F/-20.6 to -17.8 °C)
7a (0 to 5 °F/-17.8 to -15 °C)
7b (5 to 10 °F/-15 to -12.2 °C)
8a (10 to 15 °F/-12.2 to -9.4 °C)
8b (15 to 20 °F/-9.4 to -6.7 °C)
9a (20 to 25 °F/-6.7 to -3.9 °C)
9b (25 to 30 °F/-3.9 to -1.1 °C)
10a (30 to 35 °F/-1.1 to 1.7 °C)
10b (35 to 40 °F/1.7 to 4.4 °C)- 10b (35 to 40 °F/1.7 to 4.4 °C)
11a (40 to 45 °F/4.4 to 7.2 °C)