The 2012 USDA Hardiness Zone Map

Having last been updated in 1990, the United States Department of Agriculture put out a new and updated USDA Hardiness Zone Map in 2012. The map changes a few items and reflects the new warming trend in the north of the United States.

Both the older maps and the new 2012 Hardiness Zone map rely on the average annual minimum temperatures in an area, in degrees Fahrenheit and Celsius.

The Old Hardiness Map

Ranging from Zone 1 to Zone 11, the old hardiness map had zones 2 through 10 being divided into sections "A" and "B". It was not designed to reflect the internet or to be interactive with gardeners. Rather, it was meant to be in reference manuals and guidebooks. There is less precision in the older map in both range of the zone and in the weather temperatures listed. The zones listed in 1990 were based on weather patterns from 1976 to that time.

The New Hardiness Map

There are two new zones in the 2012 map, zones 12 and 13. Among the other changes, zones 1 and 11 through 13 are now divided into sections "A" and "B". It is also the first hardiness map that is interactive and has a GIS-based map where you can pull up the zone for any zip code. They also have state-by-state downloads of the map. To use the maps, the website recommends a broadband internet connection. Maps can be printed and downloaded in varying sizes and resolutions by their state or region and by the United States full map. The newer map is more precise, using 30 years of weather data from 1976 to the present. There is also more precise in marking the zones and gives better accounts of water temperature and higher elevation temperature changes.

What the Changes Mean

According to Vermont gardening consultant Charlie Nardozzi, the changes in the numbers signal many things about the environment. He is quoted in USA Today as saying "... the climate is changing. Spring is coming sooner and lasting longer. Fall lasts longer, and overall the weather is so much more erratic now." The most major of the changes is the warming (which reflects in higher zone numbers) for the northern and northeast states. California dropped in some of its more colder mountain regions.

Having a new USDA Hardiness Zone map means that gardeners and farmers that rely on knowing what can and cannot grow in their area can have more precise and correct data to base their plots on. These updates are helpful to keep track of ever-changing environmental temperatures, as seen in global warming, in tracking our history and our future.

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Sources:

USA Today: New USDA Climate Zone Map Reflects Northward Warming Trend

2012 USDA Hardiness Zone Map