In just two hours, four Friends of Dyke Marsh volunteers rescued around 55 trees from invasive English ivy on Saturday, March 16. Ivy vines snake up many trees on the George Washington Memorial Parkway, attach to the bark and put trees at risk.

In an area between Park Terrace Drive and the parkway, just south of Tulane Drive, the volunteers cut a two- to three-foot “window” around the circumference of the trees to separate the vine from its roots. Eventually, the vines will dry out and die.

English ivy, brought to North America by English settlers, is one of the most invasive and destructive plants in the region. It creates a monoculture that has minimal habitat value, gives little support to native insects and other wildlife and destroys biodiversity. It forms a dense mat that smothers and outcompetes native plants for sunlight, water and nutrients. It blocks sunlight from the tree’s bark and leaves and holds moisture that leads to rot. The vines’ weight can help topple a tree in heavy wind or snow. 

“While most people who buy English ivy have the best of intentions when they purchase it, what they might not know is that it often escapes into natural spaces and the dense monoculture it forms is really harmful to the environment,” said Mireya Stirzaker, the parkway’s natural resource specialist. Nevertheless, retailers sell it.

Youngkin Vetoed Bill

Del. Paul Krizek, Mount Vernon, introduced a bill, HB1167, in the recent General Assembly, to allow localities to ban the sale of English ivy. The bill passed in the House of Delegates 54-45, and passed in the Senate 21 to 18. But on March 14, Gov. Glenn Youngkin vetoed the bill.

His veto statement said, “While the intent to regulate invasive species is praiseworthy, this bill proposes a prohibition on a single species, potentially establishing a precedent for banning other legal plant species in the future. Such a precedent could sow confusion and inconsistency in regulations statewide. The prospect of a patchwork of laws requires small business owners and garden enthusiasts to navigate complex legal landscapes. The most effective approach to addressing this issue is education and allowing the market to determine what is best for Virginians.”

But there is more at stake than what’s available at the garden store.

Delegate Krizek responded, “I am very disappointed that the Governor saw fit to not just veto this bipartisan legislation but to make it one of his first vetoes. This bill would not have stopped English ivy but it would have allowed local governments to have the option to ban its sale and thus educate people about its harm to the environment as one of the worst invasive plants still being sold. It takes down full-grown trees and harbors rats and mosquitoes.”

Another bill, SB306, introduced by Delegate Holly Seibold and Senator Saddam Salim would require retailers to post signs indicating that plants are invasive. Youngkin has until April 8 to act. 

Virginia’s Natural Heritage Program has so far confirmed 90 invasive plants in the state (https://www.dcr.virginia.gov/natural-heritage/document/nh-invasive-plant-list-2023.pdf).

GWM Parkway Is a National Park

When the Parkway was planned, designers envisioned a unique roadway to preserve and enhance the Potomac River valley, to keep both banks of the river in public ownership and to create a grand gateway to the home of first U.S. President George Washington, Mount Vernon, at the road’s southern terminus. They integrated the road’s design with the undulating terrain following natural contours and winding in gentle curves, featured natural areas, scenic vistas, some forested areas and some grassy areas. 

Forests Are in Trouble

Studies of National Park Service forests concluded that forests in almost all of NPS’s 39 eastern parks are at risk due to invasive plants and overabundant white-tailed deer browsing (April 2023) (https://doi.org/10.1002/eap.2837).

National park forests in the eastern U.S., including the George Washington Memorial Parkway’s forests, are regenerating at low levels. In 90 percent of Washington, D.C.-area parks, the tree regenerating rates are so low that researchers anticipate widespread forest loss in the next few decades. Threats include invasive insects and plants, deer browse and climate change.

Healthy forests sustain themselves when seedlings and saplings fill a gap in the canopy after a tree dies. NPS uses a measurement called a “stocking index.” NPS says, “A park is considered to have healthy regeneration if the stocking index shows that 67 percent of its forest plots are adequately stocked with seedlings and small saplings. Since monitoring began, no [National Capital Region] park has reached 67 percent or even exceeded 30 percent. For the GWM Parkway south of the Potomac Gorge, only eight percent of plots are adequately stocked,” concluded the report.

“Threatened by large populations of hungry white-tailed deer, invasive plant crowding and other factors, seedlings struggle to grow into saplings that can eventually replace canopy trees,” the study asserts. “Over time, these stressors can reduce tree species diversity and density, negatively impacting forests and the plants and animals that rely on them.”

It takes many years for seedlings to grow into saplings and saplings to grow into young trees. In cooperation with Virginia Tech foresters, GWMP is developing a plan for managing its forests, including both natural forests and planted trees. 

Friends of Dyke Marsh volunteers work twice a month to control invasive plants. Sign up at www.fodm.org. People can also help by not planting and controlling invasive plants on private property. Invasive plants escape into forests with seeds spread by birds, wind, shoes and other methods.