USDA changes zones for Mississippi plants

Published 5:18 pm Thursday, January 18, 2024

Gardeners careful to select plants that thrive in their area have an updated U.S. Department of Agriculture Plant Hardiness Zone Map to use.

Released in late 2023, the zone map features an updated chart that was previously drawn in 2012.

Much of Mississippi is now in zone 8b. This zone has average low winter temperatures of 15–20 degrees.

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Eddie Smith, a horticulturist with the Mississippi State University Extension Service and host of Southern Gardening, said despite the adjustments made to the plant hardiness zones, most of the state will still be able to grow the same crops and plants.

“Even with warmer temperatures shown to extend further north, the options for growing tropical plants will remain the same,” Smith said. “Winter temperatures will be too low for tropical plants to survive outside without receiving some damage or being killed.”

In unveiling the new zone map, USDA announced that the 2023 map is based on 30-year averages of the lowest annual winter temperatures measured at specific locations.

Zones represent a 10-degree difference, and they are further divided into half zones based on 5-degree differences.

“The 2023 map incorporates data from 13,412 weather stations compared to the 7,983 that were used for the 2012 map,” USDA stated in a news release.

Additionally, according to USDA, “plant hardiness zone designations represent what’s known as the ‘average annual extreme minimum temperature’ at a given location during a particular time period.” Each designation is the average lowest winter temperature for a location during the 30-year period.

In general, zone 9a was previously at the very tip of the Mississippi Gulf Coast, but the zone now covers the bottom three coastal counties plus Pearl River and Stone counties.

Zone 8b was comprised of the six southernmost counties plus part of Forrest and Perry counties, then westward to Jefferson County and south.

Now, the zone is about half the state from Noxubee and Kemper counties west to Yazoo County, then north to the Delta as far as Coahoma County.

Zone 8a was previously the middle portion of the state, but the zone is now a U-shaped area from DeSoto down to Attala, up to Oktibbeha and parts of Lowndes and north to Itawamba County.

Zone 7b previously covered a portion or all of the 23 northernmost counties just east of the Delta.

Now, the zone is a randomly shaped area that mostly includes Marshall, Benton, Tippah, Alcorn and Tishomingo counties.

“When compared to the 2012 map, the 2023 version reveals that about half the country shifted to the next warmer half zone,” USDA stated in a news release. “That shift to the next warmer half zone means those areas warmed somewhere in the range of 0–5 degrees.”

It is always wise to know the USDA plant zone for a region as plants perform best when matched to the correct zone, Smith said.

Although these changes reflect a slight, regionwide warming trend, gardeners should pay attention to their own property’s microclimate.

“Many factors play into the temperature of an area, such as the topography of the land, bodies of water and more,” Smith said. “You may be able to grow things on your property that your neighbor cannot grow.”

To find the 2023 USDA Plant Hardiness Zone Maps for Mississippi and the country, visit https://planthardiness.ars.usda.gov/pages/map-downloads.