A hardiness zone is a geographically defined area in which certain types of plants can grow as defined by climatic conditions, including their ability to withstand the minimum temperatures of the zone. The hardiness zones are helpful in that extremes of winter cold are a major factor in determining whether a plant can grow in a particular location. However, there are problems with the system; most significantly, it does not consider summer heat levels. So places that may have the same minimum winter temperatures, but very different summer temperatures, are still placed in the same hardiness zone. If a plant is said to be able to grow in zone 10 it means that it can handle temperatures down to 30-40 degrees Fahrenheit (-1.1 to 4.4 C)-40 °C. To find your Hardiness Zone go to http://www.usna.usda.gov/Hardzone/ and click on the inter- active map.
