Five people gather around as one uses loppers on a vine
Natural Resources Specialist Paul Carlson, left, and Montgomery County Parks Forest Ecologist Carole Bergmann lead a Weed Warrior volunteer training, removing Oriental bittersweet and other invasive plants at Meadowside Nature Center in Rockville, Md. (Photo by Caitlin Finnerty/Chesapeake Bay Program)

Natural Resources Specialist Paul Carlson reaches up a red oak tree, his eyes fixated on the 3-inch-diameter vine that has wrapped itself around the oak’s trunk.

The vine is known as Oriental bittersweet (Celastrus orbiculatus) and its effect on the red oak is comparable to a boa constrictor’s on a human: it strangles the tree and prevents the bark from receiving sunlight, which all trees need to survive. Sometimes the bittersweet vine’s weight will even uproot the tree.

In other words, if this vine is left alone, it’s very likely that the red oak will die. Along with it will disappear the wildlife habitat, forest cover, carbon absorption, erosion control, shade and other important benefits the tree provides.

“Once you recognize it, you’ll see it everywhere,” Carlson says, in reference to the bittersweet vine. He pulls out a pruner and a folding saw and slashes away at the bittersweet. I can almost hear the red oak take a breath.

You may not realize it, but not all plants are good. Oriental bittersweet is one of dozens of non-native weeds, trees, shrubs and grasses that are aggressively invading the Chesapeake Bay watershed’s delicate ecosystems.

As their name suggests, non-native weeds are not originally from this region. Therefore, they do not have any predators, parasites or pathogens here to limit their spread. Invasive weeds:

  • Out-compete beneficial native plants
  • Replace native food and habitat that birds and other wildlife depend upon
  • Eliminate host plants for native insects such as butterflies
  • Disrupt plant-pollinator relationships, which allow native plants to reproduce
  • And do all of this at an aggressive speed

It’s estimated that invasive weed damage and control costs the United States $138 billion annually.

Ecologists, conservationists, gardeners and park maintenance staff across the Chesapeake Bay watershed are constantly looking for cost-effective ways to control these plant invaders.

Carlson and Montgomery County Parks Forest Ecologist Carole Bergmann – who can provide the name and origin of any plant I point to without consulting a field guide or iPhone app – have found an economically feasible and environmentally effective solution to the non-native weed invasion in Montgomery County, Maryland.

It’s called “Weed Warriors”: a county parks volunteer program that trains and certifies volunteers to identify and remove invasive weeds. Since the program began in 1999, Montgomery County’s Weed Warriors have put in more than 40,000 hours of volunteer service.

As the forest ecologist for all 36,000 acres of parks in Montgomery County, Bergmann realized she needed volunteers if she wanted to make a dent in the problem. “I knew that I couldn’t possibly do all the things I wanted to do without getting more people involved and giving them more responsibility and control.”

Last month, the Alliance for the Chesapeake Bay named Bergmann a 2011 “Chesapeake Forest Champion” for her work engaging more than 800 volunteers through the program.

A woman speaking and pointing instructs unseen volunteers while a man cuts vines from a tree in a forest.
Carole Bergmann started the Weed Warriors program in 1999 to enlist volunteers in the effort to tackle invasive plants across 36,000 acres of Montgomery County parkland. “I knew that I couldn’t possibly do all the things I wanted to do without getting more people involved and giving them more responsibility and control," Bergmann said. (Photo by Caitlin Finnerty/Chesapeake Bay Program)

At the final Weed Warrior training of the year in early November, volunteers follow Bergmann and Carlson through the forest surrounding Rockville’s Meadowside Nature Center, where the program is headquartered. Bergmann instructs her new volunteers to focus on vines during the winter season, and Carlson wrestles with the fall foliage to demonstrate correct vine removal tactics. The group passes around each vine and shrub, touching the bark, counting leaf lobes, and even smelling berries. It’s essential for Weed Warriors to correctly identify these plants.

“If you don’t know, don’t pull,” Bergmann implores. A plant may look like an invasive weed at first glance, but it could be an important native species that birds and squirrels depend on.

While removing all of the invasive weeds in Montgomery County is not feasible, Bergmann insists that isn’t her goal.

“The benefit of Weed Warriors isn’t just technical assistance. It’s that these volunteers understand enough to tell their neighbors, ‘Don’t buy English ivy.’”

The aggressive nature of invasive weeds requires that entire communities get on board with their extermination. In high-traffic and urban areas, such as Montgomery County, seeds of invasive plants such as kudzu and Japanese barberry often enter parks on the soles and bike tires of families and recreationists. Home owners are usually unaware that the exotic ornamental plants in their yard can invade parks and forests, overwhelming native vegetation and wildlife habitat.

“What’s really important is getting people to understand these things,” Bergmann says. “And in a way, to love the natural world.”

Bergmann knows that a sense of attachment to the natural world is what drives many Weed Warriors to volunteer. She has designed her program to foster this connection. Once volunteers complete a one-hour interactive computer training and attend a two-hour field workshop, the new Weed Warriors receive leather gloves, a hat and a “green card” that allows them to remove weeds at any Montgomery County park, whenever they want.

“People don’t always want to work in a group on the third Saturday of the month in a park across the county from where they live,” Bergmann explains. “They want to work in their park, the park that they watch their kid play baseball in every Saturday.”

Vincent Bradley of McKenney Hills decided to become a Weed Warrior after he participated in his neighborhood’s biannual cleanup this fall.

“At the cleanup, I saw this plant, porcelainberry, just taking over all of the others,” Bradley recalls.

Like many other invasive weeds, porcelainberry was planted by millions of unknowing gardeners because of its pleasant, ornamental beauty: berries ranging in color from deep purple to brilliant turquoise. But to Bradley, the plant’s destruction in his neighborhood park was anything but beautiful.

Multi-colored blue berries hang from a porcelainberry vine.
Porcelainberry and other invasive vines can girdle native trees and shrubs, smothering plants and reducing the health of the forest. (Photo courtesy of Steve Guttman/Flickr CC BY-NC-ND 2.0 DEED, cropped and toned)

Bradley began to pull on the bittersweet vines that elevated the porcelainberry. One day, a cleanup supervisor stopped him to explain that he was using the wrong technique: tugging on the vines instead of simply cutting them. Bradley decided he had more to learn if he wanted to make a difference.

“I always appreciated nature,” he says. “My father taught me about trees when I was a kid, and ever since, I’ve been interested.”

Bergmann advises Bradley and other Weed Warrior volunteers to maintain this sense of curiosity. “Come back every season,” she says. “You need to keep learning about your surroundings. It will make you happier.”

As invasive weeds continue to spread, policies are catching on. Many invasive plants are no longer sold in garden stores. Some municipalities, cities – even entire nations – are enacting legislation to limit their distribution.

For example, England has outlawed the cultivation of Japanese knotweed since 1981. In 1990, the UK classified the plant as a “controlled waste,” meaning that even the soil that once contained the plant must be disposed of at a licensed landfill.

Bergmann has some simple advice for all Weed Warriors, certified or not.

  • Be careful. If in doubt, don’t pull it out. If you’re not sure what something is, leave it be. It may be an important part of the native plant community. Bergmann encourages her volunteers to send her photographs of plants they are unable to identify.
  • Be realistic. “It’s impossible to remove every invasive. If this is your goal, you will only get discouraged. They will keep coming back, no matter what.” Instead, Bergmann tells Weed Warriors to find good trees that are still alive and cut the vines growing around them. Winter is a great time for cutting away vines.
  • Be curious. Like other plants, invasive weeds look different throughout the seasons. Attend trainings and speak with experts to learn their appearances throughout the year. Also, pay attention to what is growing in your yard and parks. You may find you have some beneficial plants, too!

Want to get involved?

You can help stop the spread of invasive plants by signing up to become a Weed Warrior. Training takes place on the last Wednesday of the month from April to October. If you can’t make the commitment to become a certified Weed Warrior, you can still make a difference. Special Project Weed Warrior events offer community members the chance to learn about and remove invasive plants in their local county parks.

No matter where you live in the Chesapeake Bay watershed, you can still help stop the spread of invasive weeds. Here are a few invasive plant resources that can help you do your part:



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