There Are Some Really, Really Old Trees In Fairfax County

The trees — old-growth Eastern hemlocks — are the kind that make you crane your head back for a better look. Their trunks are ramrod straight, with spreading branches, deep-ridged bark, and a feathery canopy of needles at the top. They grow on around 20 acres of steep hillsides sloping down to Bull Run.

The hemlocks, which are located in Hemlock Overlook Regional Park, are likely some of the oldest trees in Fairfax County. Some of them may be 250 years old, meaning that they managed to avoid the cycles of deforestation and reforestation in the eastern U.S. over the past two centuries. (Less than 1% of the forests in this part of the country are believed to be old-growth.)

On Tuesday, the hemlocks in Fairfax became the eleventh group of trees in Virginia added to the Old-Growth Forest Network, an organization with the goal of identifying and preserving at least one native forest in every U.S. county that can support one. The trees are located about a mile down the Bull-Run Occoquan Trail from the trailhead at Hemlock Overlook.

Hemlocks grow more slowly than other tree species. These smaller trees may still be a hundred years old. Margaret Barthel / WAMU/DCist

It’s remarkable to find a stand of such old, largely undisturbed trees so close to a major metropolitan area, says Brian Kane, who grew up in Fairfax and leads the network’s presence in the Mid-Atlantic region. Kane works with volunteers to identify and designate new local forests to the network.

“You know, Fairfax County people think more of Tysons, they think more of bustling urban villages,” he says. “This is really remarkable that this is here.”

Mature trees like the hemlocks boost biodiversity, create habitats for animal life, and sequester carbon. Their spreading roots help prevent streambank erosion, and their deep shade provides a cooling effect on the nearby stream, too. And they are also a connection to the deep past, says NOVA Parks Roving Naturalist Matt Felperin.

“We’re transported to a different time just by walking through here and seeing all the moss and lichen and ferns just coating the forest floor,” he says.

An informational sign explains the concept of forest succession, the idea that the composition of forests change as they age and new species dominate.
Margaret Barthel / WAMU/DCist

You might be so busy looking up that you might miss the new informational placard, which is at human level. It was installed recently by NOVA Parks, which manages Hemlock Overlook, and is the first in a series of informational signs that will educate people about the different stages of forest succession.

“Every forest has a trajectory and, if left to grow, will mature, and the trees that are there will die out and other ones will come in. It’ll become a different mix of species at every stage,” NOVA Parks executive director Paul Gilbert explains. Old hemlock trees, he says, are an indicator that the forest is “at the far end of maturity.”

The hike down to the hemlocks from the parking lot at the park helps showcase those different forest stages. The one-mile trail wanders briefly through a clearcut under some power lines, then down through a forest of mostly secondary-growth beech and poplar trees and mountain laurel.

“Beech [and] poplar tend to grow very quickly,” says NOVA Parks Roving Naturalist Matt Felperin. “It’s pretty quick into succession where they’ll show up and dominate a forest.” Beech trees can be full-grown in fifty years, Felperin says.

Second-growth beech trees fill the forest along the trail going down to Bull Run. Margaret Barthel / WAMU/DCist

By the banks of Bull Run, the trail passes by towering sycamores and tulip poplars — many of them bigger around in diameter than the hemlocks, but much younger, Felperin says.

Fairfax County and parks officials — including Board of Supervisors Chair Jeff McKay and Springfield Supervisor Pat Herrity — marked the unveiling of the placard and the hemlock trees’ old-growth designation by making the trek down.

“We must educate our people not only on the importance of preserving nature, but also our history, how we got to where we are now, and things people can do to stand up for and protect our environment,” McKay said. “These things are worth fighting for and we need the next generation to be able to do that.”

The 18-mile Bull Run-Occoquan Trail is NOVA Parks’ longest nature trail and a key part of preserving a portion of the Occoquan River watershed. The organization manages 25 miles of contiguous lands along the watershed, and more parkland along the Potomac River than any other parks agency, according to Gilbert.

Virginia bluebells along the Bull-Run Occoquan trail near the stand of hemlocks.
Margaret Barthel / WAMU/DCist

The big stretches of parkland in southern Fairfax, Kane says, are key to the county’s health and well-being.

“I look at them as kind of the lungs of Fairfax County,” he says. “The ability to have large stands of trees on hundreds of acres — they’re doing so much for the environment.”

Herrity reflected on his longstanding push to protect and maintain the county’s decision to down-zone areas in the Occoquan watershed, in an attempt to shield them from the kind of rapid development that’s happened elsewhere in the county. In the wake of neighboring Prince William County’s decision to approve a plan to allow data centers into key parts of its rural areas last year, the Fairfax Board of Supervisors unanimously recommitted to keeping its section of the watershed less developed.

“I think it’s truly important that we, you know, regularly reaffirm our commitment to these areas,” Herrity said.

The hemlocks have been part of Hemlock Regional Overlook Park, a 400-acre preserve operated by NOVA Parks, since the park was created in 1962 by NOVA Parks founder and ornithologist Ira Gabrielson, who also ran the U.S. Fish and Wildlife Service. Before that, Gilbert believes the steep hillsides saved the trees from logging or other development, despite their prime waterfront location.

These aren’t the only big trees in the D.C. region. Arlington’s Glencarlyn Park is also part of the Old-Growth Forest Network, and so is a forest of hardwood trees in a stretch of the C&O Canal National Historic Park in Montgomery County.

To see the hemlocks in Fairfax, you’re going to have to take a bit of a hike. From the parking area at Hemlock Regional Overlook (13220 Yates Ford Road, Clifton VA 20124), they’re a little over a mile along a well-maintained — though sometimes steep — trail. Admission is free to the park.