There are about 5,000 invasive plant species in the U.S. today smothering trees, trails and even waterways. Lacking the predators and pests of their native climates, these tough plants can run rampant in their adopted homes, often surviving and even thriving in poor soil and little water. As housing developments and other new infrastructure disturb landscapes and create clearings, the problem is getting worse, scientists say. Climate change has encouraged the kudzu vine, widely known as “the vine that ate the South,” to climb as far north as New England.

In 2004, neighbors in Cheverly, Md., became interested in a five-acre stretch of woods running alongside a nearby creek. “Nobody ever used them because they couldn’t get through the junk to see these beautiful trees and streams and pond,” says Cathy Smith, a freelance writer. Invasives including Chinese wisteria and Japanese stilt grass, plus trash that had snuck in from a busy highway, were overrunning the native plants.

That fall, Ms. Smith and her husband put a notice in the town newsletter asking neighbors to help them clear weeds and build a trail. To their surprise, about 15 people showed up on a Saturday morning. “It was a whole lot of people we would have never met before, but who were all interested in having a place to take their kids and walk the dog,” says Ms. Smith. “People brought weed whackers, chain saws, and we hacked our way through very dense, overgrown woods.”

Today, a regular weed-clearing takes place on the last Saturday of every month. The group calls themselves Friends of Lower Beaverdam Creek, Ms. Smith says, and brings plenty of coffee. Now, the trail is almost a mile long and growing. Homemade markers point to native trees such as paw-paws and birches that once were choked. Volunteers have noticed a return of birds and butterflies.