The newly updated U.S. Department of Agriculture’s “plant hardiness zone map” has gardeners across the nation researching what new plants they can grow in their warming regions, as the 2023 map is about 2.5 degrees Fahrenheit warmer than the 2012 map. NPR reports: This week the map got its first update in more than a decade, and the outlook for many gardens looks warmer. The 2023 map is about 2.5 degrees Fahrenheit warmer than the 2012 map across the contiguous U.S., says Chris Daly, director of the PRISM Climate Group at Oregon State University that jointly developed the map with the USDA. Daly says the new map means about half the country has shifted into a new half zone and half hasn’t. In some locations, people may find they can grow new types of flowers, fruits, vegetables and plants.
Daly says he is hesitant to explicitly attribute the specific changes from the 2012 map to the 2023 map to climate change because of the volatility of the key statistic they used to create this map. They were mapping “the coldest night of the year, each year, over the past 30 years”, Daly says, and it’s a highly variable figure. In an email, a press officer for the USDA says, “Changes to plant hardiness zones are not necessarily reflective of global climate change because of the highly variable nature of the extreme minimum temperature of the year.” But Daly says, in the big picture, climate change is playing a role in changing what grows where in the US: “Over the long run, we will expect to see a slow shifting northward of zones as climate change takes hold.”