What are the USDA Zones?
The United States Department of Agriculture (USDA) provides gardeners around North America with numerous references, including a hardiness zone map which gardeners can use to determine what sorts of plants are most likely to thrive in their area. The USDA zones are broken up by temperature: each zone is 10 degrees Fahrenheit (approximately five degrees Celsius) colder than the zone below it on the map, and that much warmer than the zone above it. Many plants are hardiness tested and list the USDA zones that they do well in, so that gardeners can make decisions about what to plant, and when. The USDA zones incorporate data which has been collected since the 1930s. The first hardiness map was released in 1960, and was continually updated until 1990, when major changes were made, including the addition of an 11th zone to the original 10. Also, USDA zones two through 10 were further divided to reflect a five degree temperature variance, which can make a big difference to some plants. Becau
