The US Department of Agriculture (USDA) recently released an updated plant hardiness zone map that reflects rising temperatures.
Whether you’re a seasoned gardener or a novice, you’ll want to know what this means for you.
Today, we’re diving into these changes so you can plan a successful growing season.
Let’s dig in!
Plant Hardiness Zone Updates are No Shock to Gardeners
Gardeners across the country were anything but surprised when the USDA unveiled an updated 2023 plant hardiness zone map. It’s been over ten years since they made changes, and many think it’s long overdue.
Anyone who’s grown fruits and vegetables for a long time has probably noticed that some old standbys no longer flourish like they once did. Certain tomato varieties that thrived in the past now burn up in the summer sun. On the other hand, folks further north might have more success with tropical plants that, until recently, didn’t take hold in their cooler climates.
About half of the 26 zones shifted into a warmer classification as temperatures have increased by roughly 2.5 degrees. The Midwest saw more changes than any other region, whereas things didn’t alter much for folks in the Southeast.
These updates came in the wake of the hottest summer on record, according to the National Oceanic and Atmospheric Administration (NOAA). And while many gardeners are excited at the prospect of adding exotic species to their gardens, others are concerned about what it means for the future.
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What are Plant Hardiness Zones?
If you’re planning for your first garden, you might not be familiar with the plant hardiness zone map. This critical tool is one of many that growers nationwide use to determine what will and won’t do well in their climate.
These lines divide the country into geographic regions with similar climates. Each is denoted by a number 4, one through nine, and a subgenre, ‘a’ or ‘b.’ The digits represent ten-degree temperature sets, and each letter is a five-degree subset. Classifications are based on the lowest winter temps in an area, and warmer locations have higher numbers.
For example, Austin, Texas, was previously in 8b. According to the new release, it’s now considered 9a.
When you look at one of these USDA maps, you’ll notice strands of color stretching across the country. The 2012 version featured much more green than the 2023 release. In fact, if you compare the two, there’s a clear shift north in many areas.
But how do gardeners put this information to use?
Since each category represents the coldest winter temps, we can use the map to determine which plants can survive in our area.
And because it’s the gold standard for growers, other resources base their recommendations on the data. Many gardening websites offer planting dates for specific crops in each locale. This information is especially helpful if you’re still cultivating your green thumb.
Pro tip: Check out the USDA’s official website to find your hardiness zone.
What Do Hardiness Zone Changes Mean for You?
Seasoned aggies may need to rethink what and when they’ll plant based on their new hardiness zone. First, check the official map and punch in your zip code to see if your area has changed. Then, consider the resources you use to determine your gardening strategy. It might be time to update if they’re based on the old listings.
This data is crucial for trees, shrubs, and other perennials. However, depending on where you live, you may find that some of your annuals can finally withstand winter weather.
Changing temperatures means different things for folks in other climates. If you live somewhere hot, like South Florida, you might struggle with scorching heat in the summer. Consider looking for heirloom varieties of your favorite veggies that can withstand hotter weather and intense direct sun.
On the flip side, folks to the north may rejoice in their newfound ability to grow more exotic plants. Additionally, productive growing seasons could last longer than they did in the past.
Finally, it’s important to note that even non-gardeners can learn a thing or two from the changes to plant hardiness zones. After all, no one is immune to the effects of rising temperatures.
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How are Plant Hardiness Zones Determined?
The USDA uses a staggering amount of information to determine plant hardiness zones. They gathered data from 13,625 weather stations over 30 years to update the maps. Then, they classify each region based on the lowest extreme temperature from each year.
That means it doesn’t consider how cold an area might get. So, even if you follow the guidelines to the letter, you could still face unseasonable cold snaps that’ll kill tender sprouts.
It’s also critical to understand that this is just one tool for gardeners and has limitations. For instance, the map doesn’t reflect precipitation, altitude, sunlight, or other factors significantly impacting plants.
Furthermore, every garden plot exists in a microclimate of some sort. Surrounding vegetation, soil conditions, salinity, and other elements will affect how well your fruits, veggies, and ornamentals grow. Keeping notes on what and when you plant and the outcomes will help you from season to season.
Predictions for Future USDA Guidelines
While the 2023 plant hardiness map gives us plenty to consider, some folks are already looking ahead. The Davey Institute, an environmental consulting firm, has an interactive layout projecting zone changes into 2099.
You can scroll through the decades to see how your region may fare in the future. It features the best- and worst-case scenarios, depending on various factors. Of course, a lot can change over 75 years, and the data has plenty of uncertainty. However, it’s interesting to see how it may further evolve in the years to come.
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Plant Hardiness Zones Could Change How You Garden
The USDA’s plant hardiness zone map is an indispensable tool for both casual gardeners and professional farmers. It provides a standard metric to streamline information from resources to consumers. After all, it’d be pretty confusing to garden in a world without it.
That being said, it’s not the end-all, be-all for growers. You’ll still need to know more about your particular microclimate to have a successful season. But, if nothing else, it gives you a great place to start your journey!
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