America's Changing Plant Hardiness Zones

Around half of Americans have been moved into a new plant hardiness zone. If you check out the USDA's new Plant Hardiness Zone Map you have a very good chance of discovering that your home is now in a new hardiness zone.

In recent years, like many gardeners, I've discovered that I can successfully sow plants a few weeks before their recommended earliest dates and that I can continue harvesting some vegetables much later than I have been able to in previous decades. Global heating has also meant that I have begun to experiment with plants which aren't usually recommended for my hardiness zone.

According to the United States Department of Agriculture I am not alone in experiencing a change in my growing seasons. Last week the USDA updated its Plant Hardiness Zone Map for the first time in more than a decade. On the new map average temperatures are around 2.5 degrees Fahrenheit warmer than on the 2012 map. This means that many gardeners are now in a new plant hardiness zone.

Plant hardiness zones are used to guide gardeners and horticulturists on the appropriate flowers and vegetables to grow where they live. The zones help gardeners understand which plants will flourish in their specific climatic conditions. They also help to guide gardeners about when they should sow and harvest different plants.

The USDA says that because the new Plant Hardiness Zone Map is based on recent changes in weather data it can't be used as evidence of global heating, which is usually measured over a longer period of time. However I don't think many people doubt that because of climate change gardeners in the United States can expect to see plant hardiness zones moving even further northwards in the coming decades.