Alien Plants Upset County Ecosystem
Parks Dept. Strategizing to Fight Invaders

By Lori Aratani
Washington Post Staff Writer
Thursday, January 3, 2008

It sounds like the title of a bad B-movie: Alien Plant Invaders. But here in Montgomery County and communities across the country, the problem of alien plants -- also known as nonnative invasive species -- is one that is being taken seriously.

County officials have allocated an increasing amount of money to help combat the problem of nonnative invasive species, which crowd out or kill native plants in local parks. Since 2006, the county has almost doubled the amount it spends on efforts to get rid of the pests. In fiscal 2008, the county will spend $125,000 on eradication efforts. But a significant gap remains. That funding level enables workers to tackle only 350 of the estimated 33,000 threatened acres of county parkland.

As officials face a $400 million budget shortfall and other programs are at risk, it's not clear whether there will be more funding to expand efforts to combat alien plants. Even so, officials with the county Parks Department are developing a comprehensive strategy to address the issue.

"It's more of a problem than it was in the past," said Carole Bergmann, a forest ecologist with the Maryland-National Capital Park and Planning Commission, who helps oversee the county's eradication efforts. "You didn't hear about this 25 years ago. If you wanted to reforest an area, the idea was just to let things grow."

These days, however, invasive plants are an increasing threat. They grow quickly and have no natural predators. On the other hand, native plants are often easy targets for hungry deer, which turn their noses up at the foreign flora and fauna, Bergman said.

"They are the cockroaches of the plant world," said Jonathan McKnight, associate director of habitat conservation for the Wildlife and Heritage Service of the Maryland Department of Natural Resources. "They can get along with whatever we throw at them."

McKnight said globalization, such as the importing of more foreign cargo, and destruction of native habitat for development have contributed to the growth of alien plants.

Bergman said that alien plants are considered one of the most serious threats to biodiversity because they can displace native plants and wildlife in an ecosystem. Some nonnative vines grow so heartily and aggressively that they can kill mature trees. Only human destruction of habitat is considered a more serious threat, other experts say.

"The problem is, the insects and diseases that would control these plants in their home territory aren't here," said Jon Traunfeld, director of the home and garden information center at the University of Maryland Cooperative Extension program. "Because there aren't any pests that can keep them in control, they spread pretty easily."

For the casual observer, the plants can be difficult to identify. Many have colorful blooms and provide a rare splash of greenery, particularly in winter when most trees have lost their leaves, Bergman said. Among the most harmful alien plants: Oriental bittersweet, porcelainberry and English ivy.

According to the National Park Service, more than 1,000 exotic plant species are considered a threat to the country's native flora and fauna.

A county staff report on the issue lists 13 parks in Montgomery that are most endangered by alien plants, including Blockhouse Point Conservation Park in Darnestown, Rachel Carson Conservation Park in Burtonsville, Black Hill Regional Park in Boyds and Little Bennett Regional Park in Clarksburg.

Animals that eat the plants' seeds or park visitors unwittingly collecting pretty plants help spread the alien species, Bergmann said. Some plants are also unknowingly sold at local nurseries or used in landscaping, she said.

The county's efforts to date have focused on getting rid of the harmful plants and educating residents to help with the problem.

In 1999, Bergmann launched the Weed Warrior program, which sends trained volunteers into parks to remove the plants. (Information about the program, which has more than 500 volunteers, is available at http://www.mc-mncppc.org.) The problem has also caught the attention of state and national officials. The Maryland Department of Natural Resources Web site ( http://www.dnr.state.md.us/invasives) chronicles not just the problem of plants, but of nonnative animals in the state.

The National Park Service offers information on nonnative invasive plants as part of its Weeds Gone Wild program. Included on its Web site ( http://www.nps.gov/plants/alien/factmain.htm) is the list "Least Wanted: Alien Plant Invaders of Natural Areas."

Not all alien plants are a danger, biologists say. Some have beneficial characteristics. For example, hydrilla, a weed that grows in the Potomac River, hinders boating but is now considered valuable because it provides shelter for fish, food for waterfowl and reduces water cloudiness.