By Beth Neels | The Associated Press
In 2023, the United States Department of Agriculture (USDA) updated its Plant Hardiness Zone Map (PHZM) for the first time in 10 years. The new map draws on more than 30 years of data and uses better technology. But it’s the work of 8,500 volunteers who make up the NWS’ cooperative network of observers, collecting daily weather observations across all fifty states, that ensures this is the most accurate map yet.
For nearly a century, the illustrated PHZM has been an essential tool, the standard for deciding what to plant and where for gardeners, farmers and horticulturists. Choosing a locally hardy plant is key to its health and yield. There are very few rules when it comes to gardening, but perhaps the most important is to work within your zone.
When shopping at the local garden center, select any plant and the label will indicate the plant’s hardiness zone range. Garden center managers generally only purchase varieties known to be hardy in their region to make shopping easier for consumers.
What is PHZM?
PHZM is a scale that growers use to determine a plant’s ability to survive in given climates and conditions. The latest version of the hardiness map uses Geographic Information System (GIS)-based data, and the finer scale of the digital version improves accuracy.
The map shows the lowest average winter temperature for a given region. For example, orange trees are hardy in zones 9 through 11, meaning they thrive in warmer climates. Apple trees thrive in zones 3 through 8 because they need cold weather (below 45°F) for at least 500 to 1,000 hours in winter to bloom and produce fruit.
Using hardiness data allows growers to avoid avoidable plant death due to unsuitable conditions and promotes a better understanding of their local environment.
How is the map created?
W. C. Woodbridge’s first global climate map, published in 1823, identifies global zones as scorching, hot, hot, and cold, among other descriptors.
The most recent map compiles information from the National Weather Service (NWS), USDA Forest Service and the U.S. Department of the Interior. This map represents weather conditions observed over the past 30 years. More than 13,000 stations provided information to OSU’s PRISM Climate Group based on the 30-year average annual extreme minimum temperature, strengthening the accuracy of the data.
These stations include two types of collection equipment: “prime stations”, which are more precise, have more sophisticated equipment and are located mainly at airports, and “cooperative stations”, which include a network of weather observations daily nationwide. .
Why is this important?
Like tomatoes, many vegetables grown in northern climates are hardy in zones 9 and 10. This distinction treats tomatoes as annuals in colder regions because they cannot survive the winter. These vegetables can be grown in portable pots that growers can move to greenhouses during harsh winter conditions.
Georgia, or the aptly named “Peach State,” has experienced excessive heat in recent years, which has negatively impacted fruit survival. The distribution of Georgia’s famous peaches represents $30 to $40 million in revenue annually.
Conversely, historically cold regions of New York State can now produce this crop. Monitoring dramatic climate changes allows growers to determine which crops will perform in a given area.
Changes to the map do not necessarily indicate global warming. The USDA states that trends in average temperatures recorded over several decades contribute to climate change data. The PHZM only covers 30-year extreme weather averages, so experts cannot draw scientific conclusions from the map’s data to support or oppose global warming.
The latest hardiness map shows new zone boundaries that contrast with previous versions. The new PHZM is generally about a quarter area warmer than that reported in the 2012 PHZM across much of the United States. Some of the changes in areas are the result of additional data sources and improved interpretation methods.
Navigating the Future of Gardening with the USDA Zone Map
The USDA Plant Hardiness Zone Map is an indispensable guide to rely on when consumers head to local garden centers or begin gardening projects. From luscious peaches to crisp apples, every plant has its ideal habitat, and this updated map identifies optimal planting locations. The map allows gardeners to make informed decisions regarding plant selection, increasing overall productivity and yield.
Gardeners across the country can use plant hardiness guides to transform green spaces into thriving gardens. As the map evolves, it remains an invaluable resource for gardeners from coast to coast.
This article was produced by Media Decision and distributed by Wealth of Geeks.
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