Updated USDA Plant Hardiness Zone Map: discovers your new zone classification
The USDA Plant Hardiness Zone Map, a crucial tool for gardeners and growers, has undergone a significant update in November 2023, marking the first update since 2012 [1]. This revised map, based on climate data from 1991 to 2020, utilizes information from 13,412 weather stations—almost double the number used in the 2012 version—making it the most accurate and detailed map ever released [1][4][5].
The new map reflects a clear shift towards warmer zones across about half of the United States. Average annual extreme minimum winter temperatures have risen by approximately 2.5 °F (1.4 °C) compared to the 2012 map, resulting in many areas moving up by half a zone, for instance from zone 10b to 11a [1]. The greatest warming has occurred in the Great Plains and Midwest, while the Southwest experienced relatively little temperature change [1]. The map also indicates longer growing seasons in some regions, like the Pacific Northwest [1][4][5].
The updated map includes more detailed information from states and territories that are not part of the continental United States, such as Alaska. This newfound precision is due to the incorporation of more recent temperature data and the use of more sophisticated mapping methods [1].
The hardiness zone is an essential tool for selecting perennial plants, as perennials need to be hardy enough to survive the winter in their planting region. For example, the weeping willow (Salix babylonica) has a planting zone ranging from zones 6 through 9 [2]. Many plants sold in nurseries have tags specifying their hardiness zone range [3].
To determine your current hardiness zone, you can use your zip code on the USDA Plant Hardiness Zone Map website [6]. It's important to choose plants with stated growing zones that include your hardiness zone to ensure their survival during winter [7]. The USDA Plant Hardiness Zone Map divides the country into 13 hardiness zones, with each zone further divided into "a" and "b" sub-zones [8].
The USDA first published a map of hardiness zones in 1960, but it was based on regional temperature information from only several hundred weather stations [9]. Since then, the map has been updated to reflect the changing climate, providing gardeners and farmers with a more accurate and reliable guide for selecting plants suitable for their region [1].
Sources: [1] USDA. (2023). New USDA Plant Hardiness Zone Map Released. Retrieved from https://www.usda.gov/media/blog/2023/11/01/new-usda-plant-hardiness-zone-map-released
[2] National Arboretum. (n.d.). Weeping Willow. Retrieved from https://www.usna.usda.gov/Gardens/PlantInfo/PlantDetail.aspx?ID=1729
[3] Home Depot. (n.d.). Plant Hardiness Zones. Retrieved from https://www.homedepot.com/c/ah/plant-hardiness-zones
[4] National Geographic. (2023). New USDA Plant Hardiness Zone Map Shows a Warmer America. Retrieved from https://www.nationalgeographic.com/science/article/new-usda-plant-hardiness-zone-map-shows-a-warmer-america
[5] The New York Times. (2023). The USDA Plant Hardiness Zone Map Gets a Major Update. Retrieved from https://www.nytimes.com/2023/11/01/science/usda-plant-hardiness-zone-map.html
[6] USDA. (n.d.). Plant Hardiness Zone Map. Retrieved from https://planthardiness.ars.usda.gov/PHZMWeb/
[7] Gardening Know How. (n.d.). Choosing the Right Perennials for Your Hardiness Zone. Retrieved from https://www.gardeningknowhow.com/garden-how/plant-perennials/choosing-the-right-perennials-for-your-hardiness-zone.htm
[8] National Gardening Association. (n.d.). Understanding the USDA Plant Hardiness Zones. Retrieved from https://www.garden.org/homegarden/article/understanding-the-usda-plant-hardiness-zones
[9] USDA. (2012). USDA Releases New Plant Hardiness Zone Map. Retrieved from https://www.usda.gov/media/blog/2012/04/19/usda-releases-new-plant-hardiness-zone-map
In light of the updated USDA Plant Hardiness Zone Map, a garden enthusiast might find it beneficial to reconsider their home-and-garden selections. As the revised map indicates a shift towards warmer zones in about half of the United States, particularly in the Great Plains and Midwest, certain plants traditionally grown in colder zones may no longer thrive as they once did due to the increased winter temperatures. For instance, one may have to reconsider planting the weeping willow, as its planting zone ranges from zones 6 through 9, if one's newly determined zone is now warmer. Thus, the updated map serves to underline the importance of researching a plant's hardiness zone before purchasing and incorporating it into the lifestyle of a home-and-garden, ensuring the plant's longevity and thus, the overall vitality of the garden.
