Growing Regions and Zones

The plant hardiness zones given in this site are based upon those from the USDA provided by the United States National Arboretum.

They provide an interactive zone map on the following website: http://www.usna.usda.gov/Hardzone/ushzmap.html

These zones are based upon the average minimum temperature range.

For a full range of temperatures and example cities, see the following web page:

There are many benefits and drawbacks associated with the use of hardiness zones, see the following web page for an in depth discussion:

A basic overview of average minimum temperatures associated with the zones is given in the following table:

Zone	Average Annual Minimum Temperature	Zone	Average Annual Minimum Temperature
1	< -50°F (45.6°C)	6	< -10° to 0°F (- 23.3 to -17.8°C)
2	-50° to -40°F (-45.6 to -40°C)	7	< 0° to 10°F (- 17.7 to 12.3°C)
3	-40° to -30°F (- 39.9 to -34.5°C)	8	< 10° to 20°F (- 12.2 to -6.7°C)
4	-30° to -20°F (- 34.4 to -28.9°C)	9	< 20° to -30°F (-1.2 to 40°C)
5	-20° to -10°F (- 28.8 to -23.4°C)	10	> 30° (-1.1°C)