We are 13 days away from the winter solstice, the shortest day of the year. And if you're anything like me, you're counting down the days until the sun stays out longer and you can start planting a garden again! But heads up, if you're planning on planting a garden next spring too, a big gardening tool just got an not so encouraging update. The USDA released an update of the Plant Hardiness Zone map on November 15th, the first update since 2012. This update brings with it signs of warming temperatures across the country. Similarly to the 2012 map, to create the 2023 map the USDA Agriculture Research Service based the map "on 30-year averages of the lowest annual winter temperatures at specific locations" (usda.gov). They then divided those temperatures into 10-degree Fahrenheit zones and then again by 5-degrees into subzones. The 2023 map upgraded the level of data collection and incorporated measurements from 13,412 weather stations, whereas the 2012 map included data from just 7,983 stations. This updated map shows what environmental scientists have been pointing to for the past two decades: consistently warmer temperatures across the United States throughout the year.
Let's compare the previous USDA Plant Hardiness Zone maps to the updated 2023 map.
1990: Ten zones of 10-degree Fahrenheit increments.
2012: The first time zones are split into half-zones.
2023: Note warmer areas in the Rocky Mountains, Alaska, and Southeastern U.S.
An example of a location that has changed zones is my current home of central South Carolina. In 2012 I was categorized as Zone 8a. Now I am squarely in the warmer categorization Zone 8b. My former home of Miami used to sit in Zone 10b but has now been overtaken by Zone 11a. Check out your location and see if you have changed zones too!
References:
https://www.ars.usda.gov/news-events/news/research-news/2023/usda-unveils-updated-plant-hardiness-zone-map/
https://planthardiness.ars.usda.gov/
https://www.motherjones.com/food/2012/01/long-overdue-plant-hardiness-map-hothouse/
https://planthardiness.ars.usda.gov/pages/map-creation
Photo by Tom Fisk: https://www.pexels.com/photo/top-view-of-green-field-1595104/
