How to Use Hardiness Zone Information
Each Zone in the system represents a region of minimum average winter temperatures. The lower the Zone number, the colder the region. Although factors other than temperature affect the ability of a plant to survive, the Zone system is a reasonable starting point for many gardeners.
The chart below shows the temperature ranges associated with the Zone system. In this chart, the Zones are divided into A and B regions, which are sometimes used to fine-tune plant recommendations.
| Zone | Average Minimum Winter Temp. | Example Cities | |
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1 | Below -50 F | Fairbanks, Alaska; Resolute, Northwest Territories (Canada) |
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2a | -50 to -45 F | Prudhoe Bay, Alaska; Flin Flon, Manitoba (Canada) |
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2b | -45 to -40 F | Unalakleet, Alaska; Pinecreek, Minnesota |
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3a | -40 to -35 F | International Falls, Minnesota; St. Michael, Alaska |
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3b | -35 to -30 F | Tomahawk, Wisconsin; Sidney, Montana |
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4a | -30 to -25 F | Minneapolis/St.Paul, Minnesota; Lewistown, Montana |
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4b | -25 to -20 F | Northwood, Iowa; Nebraska |
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5a | -20 to -15 F | Des Moines, Iowa; Illinois |
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5b | -15 to -10 F | Columbia, Missouri; Mansfield, Pennsylvania |
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6a | -10 to -5 F | St. Louis, Missouri; Lebanon, Pennsylvania |
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6b | -5 to 0 F | McMinnville, Tennessee; Branson, Missouri |
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7a | 0 to 5 F | Oklahoma City, Oklahoma; South Boston, Virginia |
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7b | 5 to 10 F | Little Rock, Arkansas; Griffin, Georgia |
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8a | 10 to 15 F | Tifton, Georgia; Dallas, Texas |
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8b | 15 to 20 F | Austin, Texas; Gainesville, Florida |
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9a | 20 to 25 F | Houston, Texas; St. Augustine, Florida |
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9b | 25 to 30 F | Brownsville, Texas; Fort Pierce, Florida |
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10a | 30 to 35 F | Naples, Florida; Victorville, California |
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10b | 35 to 40 F | Miami, Florida; Coral Gables, Florida |
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11 | above 40 F | Honolulu, Hawaii; Mazatlan, Mexico |
Continued on page 3: Plant Examples
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