Magnolia trees and camellias, once vulnerable to frost damage in Boston’s cold climate, may now thrive in the city thanks to recent changes.
The United States Department of Agriculture recently released an updated version of their “plant hardiness zone map,” the first update in ten years. The new map highlights the effects of climate change on gardens and yards throughout the country.
The difference in climate patterns is not uniform – for instance, the Midwest experienced more warming than the Southeast. However, the map will provide growers with valuable information on which flowers, vegetables, and shrubs are best suited for a specific area.
The map displays a significant value, the minimum expected winter temperature in a specific area, which plays a crucial role in identifying the plants that can endure the season. This is determined by computing the average of the lowest winter temperatures from the previous 30 years.
According to researcher Chris Daly, the lowest expected winter temperature across the lower 48 states has increased by 2.5 degrees (1.4 degrees Celsius) since the last map was released in 2012. Daly works with Oregon State University’s PRISM Climate Group, which partners with the USDA’s Agricultural Research Service to create the map.
Richard Primack, a plant ecologist from Boston University who was not part of the map project, stated that half of the United States has experienced a shift to a slightly warmer climatic zone in the past decade. He described this as a significant discovery.
Primack observed changes in his personal garden, such as the fig trees now being able to survive without needing extra measures to shield them from the cold winter weather. In addition, he has seen camellias thriving in a Boston botanical garden and southern magnolia trees enduring the last few winters without being harmed by frost. These plants are typically found in warmer, more southern regions.
According to Primack, temperatures in winter and at night are increasing at a quicker rate compared to daytime and summer temperatures. This explains why the lowest winter temperature is changing more rapidly than the overall U.S. temperature.
As the environment changes, it can be challenging for both plants and growers to adapt.
According to Theresa Crimmins, a researcher at the University of Arizona who specializes in climate change and growing seasons, the rising winter temperatures also have negative consequences. She points out that milder winters mean fewer die-offs of disease-carrying insects such as ticks and mosquitoes.
She mentioned that in certain areas, plants that used to thrive may now die due to hotter and drier summers.
She advised against planting plants that are not suitable for your current location.
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