The term "Hardiness Zone" was first developed by the US for the USDA and is now in use in many other nations. It indicates the minimum temperature of the area in question.
Hardiness Zone maps for you to find your zone:
- http://www.usna.usda.gov/Hardzone/ushzmap.html USA
- http://www.planthardiness.gc.ca/ Canada
- http://www.ahs.org/pdfs/05_heat_map.pdf USA
- http://www.gardeningzone.org/content/content.php/hardiness-zones-uk/ UK
For more information, please see http://en.wikipedia.org/wiki/Hardiness_zone