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USDA Plant Hardiness Zone Map
Plant Hardiness
Zones -- Details
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Zones 2-10 in the map have been
subdivided into light- and dark-colored sections (a and b) that
represent 5 F (2.8 C) differences within the 10 F (5.6 C) zone. The
light color of each zone represents the colder section; the dark
color, the warmer section. Zone 11 represents any area where the
average annual minimum temperature is above 40 F (4.4 C).
The map shows 20 latitude and longitude lines. Areas above an
arbitrary elevation are traditionally considered unsuitable for plant
cropping and do not bear appropriate zone designations. There are
also island zones that, because of elevation differences, are warmer
or cooler than the surrounding areas and are given a different zone
designation.
Note that many large urban areas carry a warmer zone designation
than the surrounding countryside. The map-contains as much detail as
possible, considering the vast amount of data on which it is based and
its size. |
USDA
Hardiness Zones and Average Annual Minimum Temperature Range
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1
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Below -50 F
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Below -45.6 C
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Fairbanks, Alaska; Resolute, Northwest Territories (Canada) |
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2a
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-50 to -45 F
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-42.8 to -45.5 C
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Prudhoe Bay, Alaska; Flin Flon, Manitoba (Canada) |
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2b
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-45 to -40 F
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-40.0 to -42.7 C
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Unalakleet, Alaska; Pinecreek, Minnesota |
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3a
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-40 to -35 F
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-37.3 to -39.9 C
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International Falls, Minnesota; St. Michael, Alaska |
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3b
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-35 to -30 F
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-34.5 to -37.2 C
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Tomahawk, Wisconsin; Sidney, Montana |
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4a
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-30 to -25 F
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-31.7 to -34.4 C
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Minneapolis/St.Paul, Minnesota; Lewistown, Montana |
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4b
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-25 to -20 F
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-28.9 to -31.6 C
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Northwood, Iowa; Nebraska |
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5a
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-20 to -15 F
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-26.2 to -28.8 C
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Des
Moines, Iowa; Illinois |
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5b
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-15 to -10 F
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-23.4 to -26.1 C
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Columbia, Missouri; Mansfield, Pennsylvania |
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6a
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-10 to -5 F
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-20.6 to -23.3 C
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St.
Louis, Missouri; Lebanon, Pennsylvania |
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6b
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-5 to 0 F
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-17.8 to -20.5 C
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McMinnville, Tennessee; Branson, Missouri |
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7a
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0 to 5 F
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-15.0 to -17.7 C
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Oklahoma City, Oklahoma; South Boston, Virginia |
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7b
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5 to 10 F
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-12.3 to -14.9 C
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Little Rock, Arkansas; Griffin, Georgia |
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8a
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10 to 15 F
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-9.5 to -12.2 C
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Tifton, Georgia; Dallas, Texas |
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8b
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15 to 20 F
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-6.7 to -9.4 C
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Austin, Texas; Gainesville, Florida |
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9a
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20 to 25 F
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-3.9 to -6.6 C
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Houston, Texas; St. Augustine, Florida |
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9b
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25 to 30 F
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-1.2 to -3.8 C
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Brownsville, Texas; Fort Pierce, Florida |
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10a
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30 to 35 F
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1.6 to -1.1 C
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Naples, Florida; Victorville, California |
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10b
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35 to 40 F
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4.4 to 1.7 C
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Miami, Florida; Coral Gables, Florida |
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11
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above 40 F
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above 4.5 C
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Honolulu, Hawaii; Mazatlan, Mexico |
USDA
Miscellaneous Publication No. 1475. Issued January 1990.
Authored by Henry M. Cathey while Director, U.S. National Arboretum
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