Great news for gardeners and plant enthusiasts! The U.S. Department of Agriculture (USDA) has unveiled the eagerly awaited update to its Plant Hardiness Zone Map (PHZM) on November 15, 2023. This marks the first revision of this valuable tool since 2012, offering more accuracy and detailed information to assist both seasoned and budding green thumbs.
What is the Plant Hardiness Zone Map?
The USDA's Plant Hardiness Zone Map serves as the go-to standard for gardeners and growers, helping them determine which plants are best suited to thrive in specific locations. The map, jointly developed by the USDA's Agricultural Research Service (ARS) and Oregon State University's (OSU) PRISM Climate Group, is now available online at [planthardiness.ars.usda.gov](https://planthardiness.ars.usda.gov/).
New Features and Advances
The 2023 map boasts several enhancements compared to its predecessor. It is based on 30-year averages of the lowest annual winter temperatures at specific locations, divided into 10-degree Fahrenheit zones and 5-degree Fahrenheit half-zones. The user-friendly web version, designed in a Geographic Information System (GIS)-based interactive format, now includes data from a remarkable 13,412 weather stations—up from 7,983 used in the 2012 map.
One notable improvement is the enhanced resolution for Alaska, providing a more detailed view from a 6 ¼ -square-mile area to a ¼ square mile. These updates showcase the commitment to ensuring the Plant Hardiness Zone Map remains an invaluable resource for gardeners, growers, and researchers nationwide.
Who Benefits from the PHZM?
Approximately 80 million American gardeners and growers are the primary users of the USDA Plant Hardiness Zone Map. However, its significance extends beyond gardening enthusiasts. The USDA Risk Management Agency uses the map's plant hardiness zone designations to set certain crop insurance standards. Scientists also incorporate the zones in various research models, such as those studying the spread of exotic weeds and insects.
Understanding Plant Hardiness Zone Designations
The designations on the map represent the average annual extreme minimum temperature at a given location over 30 years. They do not reflect the absolute coldest or warmest temperatures but rather the average lowest winter temperature, a crucial factor for plant survival. The map consists of 13 zones, each further divided into half zones (A and B), providing precise information for gardeners.
Changes in Zones: What to Expect
Comparing the 2023 version with its 2012 predecessor reveals intriguing shifts. Approximately half of the country moved to the next warmer half zone, indicating a warming trend of 0-5 degrees Fahrenheit. The other half remained in the same half zone, showcasing regional variations. The updates are primarily due to incorporating temperature data from a more recent time period, ranging from 1991 to 2020.
Not Necessarily a Sign of Global Climate Change
While these changes in temperature might raise eyebrows, it's essential to note that they don't necessarily reflect global climate change. The extreme minimum temperature can vary significantly from year to year, and the updates are a result of improved mapping methods and increased weather station data. Map developers caution against attributing these changes as reliable indicators of global climate change, which typically relies on trends in overall average temperatures over extended periods.
How to Access the 2023 Map
Excitingly, the 2023 Plant Hardiness Zone Map is available for free online, ensuring easy access for all interested individuals. While a paper version is not yet available for purchase, users can freely download and print copies as needed.
In conclusion, the 2023 USDA Plant Hardiness Zone Map is a valuable tool that empowers gardeners, growers, and researchers with enhanced accuracy and detail. As we delve into the world of plants, this updated map serves as an indispensable guide for cultivating a thriving and resilient garden.