Hardy har har... wait, this is serious!

Changes in climate are shifting USDA hardiness zones. Are your trees ready?

trees, climate


Andrew Dobshinsky


Danielle Capozzi


Brittany Coyle

Trees and plants are an integral part of our environment. They offer numerous benefits—from providing shade and habitat to filtering air and water pollutants to increasing property values. Yet, all trees and plants require certain conditions to grow, including suitable temperature ranges, day lengths, heat, frost, rainfall, and soil types. As a guide to understanding where similar conditions across the country exist for plants and trees to flourish, the US Department of Agriculture (USDA) developed a map of hardiness zones, the most recent version of which is from 1990. The USDA hardiness zones are often a vital resource for identifying appropriate plants species according to geographical region.

In 2006, the Arbor Day Foundation developed an updated hardiness zone map based on annual climate data observed by the National Oceanic and Atmospheric Administration since the release of the 1990 USDA map. Changes in climate have altered the hardiness zones, and the differences should serve as a wake-up call to those who are involved with selecting, planting, and caring for trees and plants. Species that may have previously thrived in an area may not do as well going forward. Some cities are trying to stay ahead of the curve. In GreenPlan Philadelphia, WRT worked with the City of Philadelphia to create a target that trees planted in the city should be able to withstand 2 hardiness zones from the current zone. Will your trees and plants survive? It’s no laughing matter.