With its higher resolution and more accurate zonal information, the new USDA Plant Hardiness Zone Map (PHZM) can be helpful as you plan your garden or landscape.
However, it’s good to remember that while the PHZM is a helpful resource, it does not guarantee that your plant will perform well in your landscape based on the hardiness zone alone. A plant’s performance is based on other factors like how it was planted, soil type, light, space, wind and overall care.
As a gardener, it’s still important to always follow the best practices of plant selection, planting and ongoing care from season to season. A plant’s growing
requirements should always match the site conditions in your landscape.
Keeping this in mind, here’s what to know about the new map and how it was developed.
What’s new about the new map? The new data is based on 1991-2020 GIS data collected from over 13,000 weather stations.
Zones 12 and 13 were added in Puerto Rico and Hawaii and can help northern gardeners decide when to bring in/put out tropical plants.
Higher resolution and more accurate zonal delineation, including in and around cities, mountains and bodies of water.
Plant hardiness zones are based on 30-year averages of weather extremes (coldest temperatures). Climate changes are based on overall annual average temperatures over 50-100 years.