Tove Danovich is a writer in Portland, Ore., and the author of “Under the Henfluence: Inside the World of Backyard Chickens and the People Who Love Them.” Yan Wu is a Post Opinion graphics reporter.
This spring, half the country will be able to consider growing plants they couldn’t have in their backyard before. In November, the Agriculture Department updated its Plant Hardiness Zone Map for the first time since 2012. The map, which tracks the average annual extreme-minimum winter temperature across the United States, showed an average increase of 2.5 degrees Fahrenheit across the Lower 48 states with some states such as Arkansas, Kentucky, Missouri and Tennessee increasing by as much as 5 degrees.
Hardiness zones indicate where plants can grow, based on the average annual extreme minimum winter temperature.
The zones are numbered from 1 (coldest) to 13 (warmest).
Each zone is subdivided into a and b, marking increments of 5 degrees Fahrenheit.
For example, zone 7b is 5°F warmer than zone 7a, …
… zone 8a is 5°F warmer than zone 7b and so forth.
How has the hardiness zone changed in your area?
See notable changes at ZIP codes: 95604, 59761
Note: 2012 data is unavailable for some ZIP codes. Some ZIP codes may not be accurately geocoded due to data limitations.
Sources: U.S. Department of Agriculture, Oregon State University, Stanford Center for Population Health Sciences, U.S. Census Bureau
People in Arkansas can now think about planting mandarin oranges in their gardens. New Yorkers might shy away from planting native sugar maples that prefer a cooler temperature. Gardeners in Massachusetts can consider planting cold-hardy camellias (once grown throughout New England in glass greenhouses) outside. We’re used to tracking climate change as a series of disasters — heat domes, deep freezes, glacial melting, floods, and fires — but the subtle signs of it have been in our backyards all along.
A map of changes in Plant Hardiness Zone, 2023 compared with 2012
Walden Pond is likely the most famous body of water in the United States, thanks to Henry David Thoreau’s writing about life from a cabin along its shore in the mid-19th century. He lived there for two years, turning his observations into the book “Walden.” The records Thoreau made during his daily four-hour walks around the pond during that time and beyond have become vital to scientists studying climate change. He noted the dates that various species of bushes and deciduous trees sprouted leaves, when wildflowers bloomed, and the arrival dates of migratory birds.
Plants bud an average of 18 days earlier than 1950s
When scientists compared modern flowering times with what Thoreau recorded, they discovered that plants bud an average of 18 days earlier now than they used to — with real impacts on young insects that rely on young leaves for sustenance and migrating birds that rely on the insects during their long journeys.
Even if you’re not a gardener, it’s worth paying attention to the plants, animals and insects around you because, in 10, 20 or 30 years, they might look quite different than they do today.
This time of year, I can’t help but remember the winters of my childhood, where sidewalks sometimes resembled tunnels dug out from the snow. In midsummer, when I return to the Midwest where I grew up, I yearn for sightings of fireflies that used to swarm so thick they were easy to catch in jars. When I see lightning bugs now, they look more like fleeting specks of embers from a bonfire.
In her excellent book, “Slow Birding,” Joan E. Strassmann recommends tracking the birds that visit your own backyard — not just a checklist of species but taking note of moments, such as the day each year when migrating birds appear and leave. In my own yard, I get excited every fall when the trees fill with whinnying robins and cedar waxwings that come to eat the ripe crab apples. These are the kinds of observations that made Thoreau’s data so important to modern climate scientists and can still can help you become more attuned to the changes in your backyard or neighborhood.
The updated planting zones are a blessing and a curse for gardeners who can experiment with new types of plants but might find that prized trees or shrubs aren’t doing as well as they were a decade or two ago. It’s a more fraught question for native-habitat restoration. If native sugar maples no longer thrive in New York state, what does that mean for the ecosystem that has come to rely on them?
In the Pacific Northwest, where some areas had minimal or no changes in their growing zones, iconic western red cedars are still dying because of drier summers. Planting a native sapling is increasingly a gamble and some scientists are beginning to wonder whether native plants — like my nursery-purchased perennials — should be shifting habitats, too.
The most uncomfortable thing about the updates to the USDA growing zones is that they aren’t a forecast; they are based on data from the last 30 years. For people who have discovered their zones have updated — by a little or a lot — the change is one that has already taken place. That’s why many avid gardeners weren’t surprised by the updates and some nurseries were already discovering that plants that shouldn’t do well locally are nonetheless surviving.
We live in an age of solastalgia, a term that refers to missing an environment that no longer exists. It’s commonly used to describe the alterations that climate change has made to places we know and love — mild summers that have become unbearably hot, or snowy winters that are now simply cold and sometimes slushy. The time to notice and appreciate the world around us is now. The only thing sadder than missing something that’s gone away is not realizing that so much has already changed.
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