As the old saw goes, you might not see the forest because of all the trees. Today, it’s hard to spot the trees because of all the plants: tangling vines that girdle timber like an octopus; wandering weeds that weave forest floors with stringers and leaves; thorny bushes and sharp grasses that rob flora of essential sunlight and nutrients.

This photosynthetic riffraff, better known to biologists, foresters and ecologists as invasive plants, have been sprouting since at least since 1492, when explorer Christopher Columbus landed in the Bahamas with wheat, barley and rye. Invasive plants proliferated during the 19th century as botanic gardens collected plants from throughout the globe. They were studied, classified, reproduced and sometimes introduced commercially as ornamental shrubs and household plants. Birds and animals helped to spread their seeds.

“It’s a global issue,” said Chris Bright, a naturalist with Earth Sangha, a Fairfax, VA-based Buddhist organization that, along with other local environmental groups, is working to rid local woodlands of foreign plants. “If you could pluck down a Jamestown settler in a modern forest, he wouldn’t recognize it.”

That’s because the forests experienced by North America’s first settlers had taller, old-growth trees with robust canopies and less-dense floors. Much of the choking nutrient-robbing underbrush was removed by fire, which burned unhindered for days, Bright said.

The green mess that chokes many of today’s forests and fields is a more recent phenomenon—a spin-off of Jet Age prosperity where goods, materials and tourists crisscross the globe in hours—along with plants and seeds.

Earth Sangha musters up to 500 volunteers who comb through Fairfax County parks ripping out weeds, pulling vines and clipping brush. They restore the land with native species the organization grows from seeds at its own nursery.

Fairfax is a microcosm of a huge international problem. From South Africa to Australia to North Carolina’s Great Smoky Mountains, millions of dollars are being spent to restore native vegetation.

How bad is it?

The U.S. Department of Agriculture estimates that invasive plants are costing taxpayers more than $10 billion dollars each year in lost agricultural and forest productivity. These non-native species thrive because they’re removed from the natural predators and other conditions that limited their growth elsewhere.

Ecological destruction by invasive plants is second only to the environmental havoc caused by people, according to The Nature Conservancy. Exotic plants clog waterways, destroy crops and prevent trees from germinating through vine-infested forest floors, a Cornell University study concluded.

“Invasive species are the greatest environmental threat of the 21st century—more than global climate change,” said Tom Stohlgren of the U.S. Geological Survey.

Yet these findings don’t discourage the legions of weed warriors who toil in the region’s woods and parks with the hope of turning back a tsunami of green interlopers. Earth Sangha, for example, which concentrates on the more than 20,000 acres that make up Fairfax County parks, has experienced some success, particularly in removing English ivy and garlic mustard.

“Control is very labor intensive,” Bright said. “You need lots of hands on the ground. You generate huge biomass. You have to bag it for the landfill or compost it. The heat of composting will kill the seeds.”

Surprisingly, winter is an ideal time to remove the foreign plants because they’re easy to spot. Unlike native species, invasive plants are not as dormant during the cold months and remain green. “A good test of the woods in January is if everything looks brown, it’s OK,” Bright said. “If you see green, it’s invasive.”

One has to be an optimist. A winter drive along the Baltimore-Washington Parkway between the District and Baltimore, for instance, reveals miles of roadside woods clogged with green vines and thickets. Taming that jungle might seem overwhelming, even impossible. But, when it happens, the result is startling, even beautiful.

Take Woodworth Park in Cheverly, MD. This 15–acre wooded buffer wedged between a residential neighborhood and Route 50 is slowly returning to its natural state thanks to The Friends of Lower Beaver Dam Creek.

Thick rows of wineberry—an invasive plant that kills native blackberry—were removed along a bordering street. Coils of Japanese honeysuckle that obliterate forest vistas lower than eye level were uprooted. Tentacles of English ivy that blanketed the forest floor and curled like rope around trees were cut away. Garlic mustard, a plant with scalloped-shaped leaves that hovers near the ground, was plucked by hand and bagged.

The group landscaped steps into a small hill that leads to an inviting trail the volunteers blazed along a shallow winding creek. The creek, which roughly divides the park in two, eventually feeds a tributary of the Anacostia River.

The reclaimed land has a peaceful resonance. Trees stand out. Space, depth and light are abundant. Smaller trees such as sassafras, hickory, hornbeam and a dogwood—discovered on a hillside after the thickets were cleared—were labeled. The forest returned to its rightful winter hues—brown, black and gray.

Continue along the trail, and the woods are again eventually consumed in entanglement, like a net cast over the forest. Nearly every square foot sprouts something green. There is movement in the underbrush, though. Several hunched-over volunteers, nearly hidden by the invasive greenery, come into focus. It’s the front line, where the work continues.

Dan Smith, co-chairman of the Friends of Lower Beaver Dam Creek, and Dave Kneipp, both of Cheverly, work their orange “weed wrench,” a crowbar-like tool that uproots plants, under a multiflora rose. Smith pulls back on the long handle that acts as a lever and the plant rips from the soil, revealing its yellowish roots and stem.

“It does seem overwhelming at times,” Smith said, surveying all the vines and brush.

“But we feel like we’re making a difference. After you remove that nasty multiflora rose and the next year you see a beautiful blooming [native] plant, you realize the difference.”

Gabe Horchler, perspiring in his white T-shirt during an unusually warm December afternoon, used a spade to remove Japanese honeysuckle. Several green piles of the harvested menace surrounded him, proof of a productive day. “It sometimes seems insurmountable,” the Cheverly resident said.

The group has made great strides in eradicating the ivy and honeysuckle only to be faced by two more setbacks. “We’re losing the battle on garlic mustard and stiltgrass,” says Marc Imlay, an Anacostia Watershed Society biologist and Lower Beaver Dam Creek volunteer. “We don’t want to miss a single plant.” A bill to prohibit nurseries from selling English ivy was defeated last year in the Virginia legislature, he said.

Garlic mustard was introduced to the United States by Russian immigrants who used the green in salads. Stiltgrass doubles the soil’s nitrogen, leading to more nutrient runoff into the Chesapeake Bay. There, it spurs the growth of aquatic plants—algae—which ultimately die and decay in a process that removes oxygen from the water, killing the fish. About 10 percent of New Jersey is overrun by the grass, Imlay said.

Removing invasive plants in the winter makes the spring cleanup more complete because new sprouts are easier to spot and remove. Doing a massive winter removal is also less exhaustive, Imlay said. “It’s a two-step process: first year messy, next year neat. The secret is to get it all in five years.”

That, he said, is how long it typically takes to remove garlic mustard—often the toughest invasive to get rid of—from a site.

Like many conservation groups striving to raise an issue, the sweat that goes into reviving and showcasing these natural enclaves is aimed at creating community awareness. That’s the key to taking back and sustaining these habitats, said Dan Smith.

“People need to realize they have these areas in their backyards,” he said. “They need to get connected to the streams and rivers. We won’t get people to cleanup the Anacostia or the Bay unless we get them involved.”