Check the updated 2023 Hardiness Zone Map to learn which plants will thrive in your area and which will not.
Every ten years or so, the USDA updates its Hardiness Zone Map. The map is the standard by which gardeners can determine which perennials and annuals will thrive in their location – and, importantly, those that may not. According to the USDA, “The new map—jointly developed by USDA’s Agricultural Research Service (ARS) and Oregon State University’s (OSU) PRISM Climate Group—is more accurate and contains greater detail than prior versions.”
The 2023 Hardiness Zone Map’s interactivity is far better than previous maps. As seen below, you can type in your zip code, find your hardiness zone, and see how it has changed since the last map was issued in 2012. Alarmingly, my area in Pennsylvania has again changed and shows an average warming of 3 degrees Fahrenheit. Before 2012, my area was Zone 6 – in 2012, we graduated to Zone 6b and are now Zone 7a. That may explain why some seeds and bulbs rated for warmer climates now frequently survive winter.
Hardiness Zones Explained
USDA Plant Hardiness Zones represent the average annual extreme minimum temperature at a given location during the past 30 years. The designations do not reflect the coldest it has ever been or will be in a specific zone but simply the average lowest winter temperature for the area for the measured period. Low temperature during the winter is an important metric, as it determines whether a plant can survive the coldest weather in a particular location.
Did Hardiness Zones get warmer since 2012?
Almost half of the country is now in a slightly warmer zone. As with the previous map in 2012, the 2023 version has 13 zones across the United States and its territories. Each zone is split in two, designated as “A” and “B” (6a, 6b, 7a, 7b, etc). Compared to the 2012 map, the 2023 hardiness zone map shows that about half of the country shifted to the next warmer half zone and warmed (on average) between 0-5 degrees Fahrenheit. But not every zone that warmed necessarily changed.
Temperature updates to plant hardiness zones are not necessarily reflective of global climate change because of the highly variable nature of the extreme minimum temperature of the year, as well as the use of increasingly sophisticated mapping methods and the inclusion of data from more weather stations. Consequently, map developers involved in the project cautioned against attributing temperature updates made to some zones as reliable and accurate indicators of global climate change (which is usually based on trends in overall average temperatures recorded over long[er] time periods).
USDA Agriculutural Research Service
See the official 2023 USDA Hardiness Zone Map.
So consult the revised hardiness zone map before choosing plants this year, and read the plant tag, catalog description, or seed packet to make sure your plant will survive winter in your hardiness zone!