The U.S. Department of Agriculture (USDA) recently released a very new, more accurate version of its Plant Hardiness Zone Map (PHZM), updating this valuable tool for gardeners for the first time since 2012. In Westchester, zones really have changed.
For example, in Larchmont, Mamaroneck, and New Rochelle, the 2023 plant hardiness zones have shifted from 7a to the next warmer half zone 7b, which means these planting zones have warmed and now the coldest temperatures are at 5-10 degrees Fahrenheit. (They used to be at 0-5 degrees.) As a result, different plant species that prefer warmer zones may do well, while others may not thrive at all.
On the map’s new website, you can search by zip code to find your current zone. Also, a helpful YouTube video shows how to use the map and demos some of its newer features. 
The 2023 map—jointly developed by USDA’s Agricultural Research Service (ARS) and Oregon State University’s (OSU) PRISM Climate Group—contains greater detail than prior versions. When compared to the 2012 map, the 2023 version reveals that about half of the country shifted to the next warmer half zone, and the other half of the country remained in the same half zone.
However, USDA experts say these temperature updates to plant hardiness zones are “not necessarily reflective of global climate change.” In fact, given the use of increasingly sophisticated technology and mapping methods and the inclusion of data from many more weather stations,”the map’s developers caution against attributing temperature updates made to some zones as reliable and accurate indicators of global climate change.” Global climate change is based on data from overall trends in average temperatures recorded over very long time periods.
The new map is available online at https://planthardiness.ars.usda.gov/
