Did You Know That USDA Hardiness Zones Have Changed?

What it means for your garden.

August 14, 2017

(Full USDA Hardiness Zone map)

If you started your garden before 2012, you might be surprised to learn that your hardiness zone has changed since then.


One of the most important factors in which plants will do well in your garden is how cold the winters are. Maps created by the National Oceanic And Atmospheric Administration (NOAA) that look at 30-year averages of the coldest days of the year show that since the 1980s, hardiness zones have been steadily moving northward and upward in elevation—and many parts of the country have experienced enough of an uptick in overnight lows and winter temperatures to move up a zone. (You can check out the shifts in U.S. planting zones in this map.)

(Whether you're starting your first garden or switching to organic, Rodale’s Basic Organic Gardening has all the answers and advice you need—get your copy today!)

What does this mean for your garden?

First, the good news (because there is some). Shifting temperatures, especially in so-called “marginal” areas of the map (where one zone abuts another) mean you can expect success with a wider range of plants than before—in parts of northwest Montana, which have been reclassified from zone 5b to 6a, longer summers and shorter winters have made it possible for farmers to grow artichokes and ginger, WBUR reported this summer.

Related: How To Grow Ginger Indoors

The bad news: trees like sugar maples that depend on frigid winters to fend off pests and diseases, have been perishing in the southern reaches of their ranges. For orchardists, wildly fluctuating winter temperatures create a greater risk of frost damage, as one cold night can decimate an entire orchard's too-early blossoms. And gardeners of all stripes have to deal with more insect pests, which are better able to thrive and spread throughout natural landscapes, unchecked by a winter freeze.


What should you do about it? First of all, there’s no need to rip out what’s doing well in your garden if your zone has changed, though you might want to check out these tips on how to plant a garden that can accommodate global warming. Keep gardening organically—organic gardening and farming methods help fight climate change.

Related: Why 2017 Is Going To Be A Really Bad Year For Lyme Disease—And How You Can Protect Yourself

And if you’re considering planting a tree, which will need to weather long-term climate changes, be sure to consult the Arbor Day Foundation’s 2015 Hardiness Zone Map (which uses more recent data than the U.S. Hardiness Zones map, which was last updated in 2012) to see if your zone has shifted, and check out their tree finder, which can recommend the best tree for your zone.