New hardiness zone map will help US gardeners keep pace with climate change
Southern staples like magnolia trees and camellias may now be able to grow without frost damage in once-frigid Boston.
Summary: most areas of the US now fall into a hardiness zone that is one step warmer than shown on the 2012 map. But...
"It's calculated by averaging the lowest winter temperatures of the past 30 years."
Keep in mind that the average over the past 30 years is not actually what you are seeing in 2023, so the article's title is somewhat misleading.
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