Trees in Montgomery County are facing several threats including invasive plants and bugs, climate change and development—even as the Metropolitan Washington Council of Governments encourages its jurisdictions to try to ensure at least 50% tree canopy coverage for the region through 2050.
In April, the council announced its regional tree canopy goal along with a report detailing the amount of tree canopy loss and gains in jurisdictions across the region. According to the tree canopy report, Montgomery County lost nearly 5,800 acres of tree canopy from 2014 to 2018, decreasing from 48.6% to 46.7% of tree canopy cover.
“Tree canopy is incredibly important to Montgomery County,” said Sarah Kogel-Smucker, the county’s climate change officer. “Trees are climate superheroes that remove carbon pollution from our atmosphere while providing the shade needed to withstand hotter temperatures.”
Kogel-Smucker said the county is “strongly supportive” of the council’s tree canopy goal and noted representatives from the county’s Department of Environmental Protection served on the council’s committee charged with developing the goal.
Experts say trees are critical for fighting the impacts of climate change such as extreme heat and the urban heat island effect and are beneficial for human and environmental health. Heat islands are areas that experience higher temperatures due to a reduced natural landscape and higher concentration of structures like buildings, roads and infrastructure that absorb and re-emit the sun’s heat, according to the U.S. Environmental Protection Agency.
The county’s canopy loss can be attributed to several causes, including non-native invasive vines and insects impacting the tree’s ability to thrive, drier summers, warmer winters and infill development, according to local environmental officials and tree experts.
“As we have warmer winters, the [invasive] vines die out less,” Kogel-Smucker said. During colder winters, “a lot of the time the [invasive] vines would die out, but now they’re not [dying out] as much, so it’s really becoming a bigger threat to trees.”
One way the county is working to combat invasive vines is through Montgomery Park’s Weed Warrior program. Kogel-Smucker said program volunteers can receive training on how to best manage the non-native invasive vines and protect trees.
According to Colter Burkes, an urban forester with Montgomery Parks, non-native invasive plants are a “big issue” for the county’s forested areas. Forest ecologists with the parks department’s Park, Planning & Stewardship Division help tackle non-native invasive plant issues and manage the Weed Warrior program, Burkes said.

Vines such as the invasive bittersweet and Mile-a-minute vines quickly grow on trees, reaching and killing the canopy, he said. Invasive vines can also inhibit inspections on trees deemed to be hazards and may need to be removed, he said.
In addition to vines, an invasive beetle called the emerald ash borer has recently wreaked havoc on the county’s ash trees, according to Burkes. The parks department has been dealing with the invasive beetles since 2015 and has removed around 5,000 infected ash trees in parks and trail systems across the county, Burkes said.
The emerald ash borer is a wood-boring bug responsible for the death and decline of tens of millions of ash trees in North America, according to the U.S. Department of Agriculture. The beetle lays its eggs in the trees’ bark. When the eggs hatch, larvae burrow into and feed on the tree, causing it to deteriorate or die.
Burkes said the county is still dealing with the impact of emerald ash borer infestations and the parks department recently removed a dead ash tree from Brookside Gardens in Wheaton Regional Park.
Another threat to county trees is drier summers, according to Burkes. Within the last five years, he has seen oak trees dying and declining in health, especially older, larger trees and white oaks, the official state tree of Maryland. Burkes said hotter and drier summers are “stressing out the trees” and causing them to be more vulnerable to other pests and diseases.
“We’ve been trying to do something to help protect the trees that are still healthy,” Burkes said, noting that the parks department keeps a tree inventory of the trees in its parks and helps foresters manage tree health. “We have some important groves of oak trees and white oak trees in our Jesup Blair Park in Silver Spring … and parks across our system that have large white oak populations that make up a large part of the canopy of the park.”
To protect the existing oaks, Burkes said the parks department has been spreading extra mulch near the trees and trying to improve the soil. In some cases, the parks department is also applying soil and tree injections that help protect the trees from wood-boring insects and increase “fine root growth to help give resiliency to the trees so they’re not as adversely affected,” he said.
Infill development is also impacting the loss of tree canopy, according to Michael Knapp, chair of the councils’ Regional Tree Canopy Subcommittee and a tree specialist with the county Department of Permitting Services. Infill development is the practice of building new homes or buildings on properties formerly housing structures that were built from the 1950s to the ’80s.
The process, a popular development method in the county and across the region, “makes it difficult to preserve existing [tree] canopy,” Knapp said.
“Once a tree has grown and matured in these older neighborhoods, its root system [doesn’t] pay attention to property lines. [The roots] will develop in a circular area spreading out from the tree and … into your neighbor’s property,” he said. “One large tree can have a root system that extends into, maybe four different lots. So, if you go in and build on a lot, it is very easy to not only remove the trees that are on the lot but also impact the health of trees on adjacent lots.”
Knapp, the primary author of the council’s tree canopy report, said it will be critical for jurisdictions to focus on programs that “try to mitigate the social, socio-economic impacts that infill development has on adjacent properties” and to concentrate on tree replacement.

According to Knapp, planting new trees will be one of the main focuses in efforts to reach the 50% tree canopy cover goal, especially with the council’s regional housing target for the region. Montgomery County’s housing target is to build 41,000 household units between 2020 and 2030.
“You want to try to preserve as much of our existing trees that we can. However, that’s very challenging on different types of land use, especially in high urban conditions of new development,” Knapp said.
As housing becomes more dense, preserving trees becomes more challenging, he said. “There’s a biological reality that you have to face there and because of that, tree planting is going to represent probably the lion’s share of how we’ll be able to maintain that 50% canopy,” he said.
The county has already been working to increase its tree canopy and retain forests, according to Kogel-Smucker. One goal of the county’s 2021 Climate Action Plan is the sequestration of carbon, which can be achieved through efforts to retain and increase forests and tree canopy. Doing so can help reduce the risk of extreme precipitation and extreme heat stemming from a changing climate, the plan says.
Overall, the county aims to be a leader in addressing climate change and has “some of the most aggressive climate action goals in the nation,” Kogel-Smucker said. One of the main goals of the plan is to reduce the county’s greenhouse gas pollution by 80% by 2027, and 100% by 2035.
In addition to its climate action plan, the county has already been addressing tree loss through its laws concerning forest conservation, tree canopy and roadside tree protection.
In March 2023, the county’s forest conservation law was updated to include amendments that are “intended to achieve no net loss of forest,” according to Montgomery Planning. Since 1992, the forest conservation law has preserved more than 2,500 acres of existing forest and more than 2,500 acres of planted forests across the county, according to Montgomery Planning.
The tree canopy law, which took effect in 2014, also requires property owners to plant new shade trees during development to help “offset the impacts of development on the natural environment.” Under the law, the Tree Montgomery program was created to facilitate the process of planting trees by providing free shade trees and planting services.
Montgomery Planning’s Reforest Montgomery program offers property owners incentives to plant trees within the county, such as discounts, and allows them to apply for free reforestation. A map on the department’s website shows residents which programs they are eligible for based on their home address.
“Trees are climate superheroes,” Kogel-Smucker said. “Climate change can seem like a big problem but there are little things that we can all do that add up to a big difference.”