Bad news for anyone who has already gotten roots in the ground: Fairfax County’s window for planting trees has shifted back following a record-hot summer.
Forest Conservation (FCON) staff in the county’s Department of Land Development Services (LDS) updated its policy this spring to designate Oct. 1 through May 31 as the recommended time frame for planting trees, pushing back the previous start date of Sept. 1 and extending it through the winter.
Driven by an “increasingly warming climate,” this is the first time that the county has revised its tree-planting window in at least three decades, according to a county press release.
“Adapting to the changing climate is crucial for the success of establishing newly planted trees,” LDS Forest Conservation Chief Adam Lipera said in the release. “Warmer temperatures and shifting weather patterns, extreme weather events and changing soil conditions are just a few of the challenges that can significantly impact tree growth and survival as a result of climate change.”
In the past, the county has concentrated tree plantings in the fall to avoid the summer heat — which reduces saplings’ chances of survival — and ensure the trees can properly take root before winter sets in.
However, National Weather Service data indicates that locally, temperatures have increased 4 to 6 degrees on average in September since 1962, and they’re projected to rise another 4.4 to 9 degrees by 2085, Fairfax County says. In addition, winters have become milder, with snow seeming more like an occasional phenomenon than a staple of the season.
“The extension of the tree planting window through winter is a result of the ground no longer freezing through the winter months, another impact of climate change,” county staff said.
Fairfax County isn’t alone in adjusting its expectations for the best time for planting. Last November, the U.S. Department of Agriculture updated its Plant Hardiness Zone Map for the first time since 2012, shifting about half the country to the next warmest half zone after they saw temperature increases of up to 5 degrees Fahrenheit.
Fairfax County moved up to Zone 7b, indicating that the average lowest temperature is now 5 to 10 degrees Fahrenheit based on the past 30 years of data. The map is used by gardeners and other planters as a guide for determining which perennial plants are likely to survive in their area.
“We are projected to be in Zone 8 within the next few decades,” the county said in its press release. “When you are selecting a tree, it is recommended that you choose a tree that can thrive in zones 7b and above.”
According to the release, county staff are researching the resilience, adaptability and migration of over 300 tree species to shape future recommendations for which ones to plant.
The county recently instituted new requirements for trees in parking lots and along streets, and staff are also working to plant trees in communities where heat islands are prevalent. Several schools are slated to get new trees this year, including Annandale Terrace Elementary, Greenbriar West Elementary, Franklin Middle, Lake Anne Elementary, Clearview Elementary and Liberty Middle.
The ongoing lack of rain could also affect the viability of trees and other plants. Western Fairfax County is officially in a moderate drought, according to the U.S. Drought Monitor, which updated last Thursday (Sept. 12).
A drought warning issued this summer for much of Virginia was lifted in August after the state caught some remnants of Tropical Storm Debby. But the D.C. region has seen essentially no rain so far in September, though the drinking water supply remains stable for now.
The temperature range for Zone 7b on the U.S. Plant Hardiness Map has been corrected.
