Motorists zipping along the Jones Falls Expressway on their way into and out of the city may not have noticed, but there's an extreme greenery makeover under way there.
It's not exactly scenic right now — just long brown swaths of dead vines, tree stumps and brush along each side of the highway. Killing off the existing vegetation, however, is the opening move in a months-long landscaping effort by the State Highway Administration to replace thickets of exotic, invasive vines with new grass and trees, many of them native to Maryland.
"We're trying to be good environmental stewards, even though it doesn't look like it," said Ken Oldham, chief of landscape operations in the state highway's office of environmental design.
The four-mile stretch of Interstate 83 from the city line to Interstate 695 had become overgrown with a pair of imported Asian vines, porcelain-berry and Oriental bittersweet, he said. The $595,662 contract to clean up the I-83 jungle is similar to roadside landscaping projects the SHA is doing around the state.
"These are exotic, invasive plants that grow up in the tops of trees, tend to weigh them down, then kill the trees as they compete for light," the state highway official said.
Invasive plants imported from elsewhere — often intentionally for what seemed like benign purposes at the time — have spread across the landscape, crowding out native vegetation and often depriving native insects, birds and animals of the food and shelter they rely upon. Conservation groups and government alike have spent millions trying to protect natural areas from foreign incursions, and have expanded the effort to include roadsides and highway medians.
Porcelain-berry is a woody grapevine imported from Asia in the 19th century for use in gardens. It's since gotten into the wild, though, and now grows from New England to North Carolina and in Michigan, according to the Plant Conservation Alliance.
Nineteenth-century gardeners brought in Oriental bittersweet, too, because of its showy reddish berries. Still planted by some as an ornamental, the vigorously growing vine infests an even broader swath of the United States, from the Northeast to the Midwest.
To get rid of the tangle of vines, crews repeatedly sprayed the highway right-of-way this summer with a weed killer, Milestone VM. The herbicide, made by Dow AgroSciences, is touted by the company for controlling weeds on farmland and roadsides. The active ingredient is aminopyralid, a chemical developed and patented by the company.
It can irritate skin and eyes on contact, but is classified as "practically non-toxic" by the U.S. Environmental Protection Agency. And according to company literature, it has "very low" toxicity to birds, fish, mammals and aquatic creatures.
Any use of pesticides, though, bothers some environmentalists.
"There are much less-polluting ways of killing invasive weeds, but those methods take a lot more time," said Eliza Smith Steinmeier, the Baltimore Harbor Waterkeeper, who monitors the Jones Falls and other streams that feed into the harbor. Vines targeted for removal can be cut at the base and have herbicide applied directly to their stump, she added, making broader spraying unnecessary.
Oldham said crews used hoses to direct their chemical spray and avoid hitting desirable plants. They also did not spray within 50 feet of any bridge over water that might reach the Jones Falls. And they stopped work whenever it was breezy or hot, to minimize the chances the chemical mist would "drift" offsite.
Marc Imlay, an officer in the Maryland chapter of the Sierra Club and the Native Plant Society, praised the SHA's efforts to reclaim roadsides from invasive vegetation, though he said he was not familiar with this project.
"SHA is very careful in my experience in using the right herbicides," he said. "They have a good history."
While some have tried non-chemical means of controlling non-native vegetation by importing the insects and other organisms that feed on it, Imlay said such efforts are fraught with risk. They have to be carefully researched in advance, he said, to avoid compounding the problem by releasing another exotic species into the wild.
Oldham said someone even suggested using goats to chew their way through the vines and brush the state wanted to remove. The SHA has used goats on projects before, but officials ruled it out this time for safety reasons, not wanting to distract drivers on what is already a challenging, winding throughway.
Besides killing the vines, crews cut down many trees, Oldham said. Some were deemed a safety hazard because they were close to the highway, while others were dead, or nearly so, from being overgrown by their invasive neighbors. They're to be replaced with up to 1,000 new trees — a mix of Southern white pines, Norway spruce, oaks and maples.