USDA Releases New Plant Hardiness Map
The United States Depa rtment of Agriculture (USDA) has released the first new USDA Plant Hardiness Zone Map since 1990. As gardeners, farmers and others involved in growing pursuits are aware, the Plant Hardiness Map is used to determine where certain species are most likely to thrive, and this new edition of the map reveals that those locations have shifted.
The 2012 map was crafted using weather data from 1976-2005, which has resulted in many zone borders moving north. Two new zones have also been established: Zones 12 and 13. These new zones represent areas with annual extreme minimum temperatures above 50 degrees and 60 degrees Fahrenheit and only appear in Hawaii and Puerto Rico.
For the first time, the USDA Plant Hardiness Zone Map also utilizes Geographic Information System (GIS) technology and has been designed specifically for the internet — no posters will be produced of the map. These two technological changes mean that the map reveals finer detail than ever before. One can drill down to an individual town or city to discover that its zone is different than the one for the surrounding countryside because of urban-heat-island effects. Also, finding zone information is easier than ever with a zip code finder feature on the map’s website.
Remember that if your zone has changed, it doesn’t mean existing flora that is not zone compliant should be removed or will start to die. It just means that moving forward, you should pursue trees, plants and flowers that represent your new zone. For a list of ratings for selected woody plants, visit the U.S. National Arboretum’s website.