Japanese weed a growing problem at Wilson Creek

Jul. 20, 2014 @ 08:54 AM

In the 1920s, Bill Crump ordered a packet of seeds from a Sears Roebuck catalog to help him stave erosion after a flood washed through his woodworking mill in Cary’s Flat, near the headwaters of Wilson Creek.

In the 70 years since then, the plant that grew from those seeds, Japanese knotweed, has multiplied exponentially, migrated down the creek and taken up residence along uninhabited stream banks.

Today, what was supposed to be a fix has become a big problem for the ecology in the Wilson Creek area.

Japanese knotweed, now known around Wilson Creek as “Bill Crump weed,” is used as a decorative plant or to help control erosion. Because it is not native to this area and has no natural enemies, it is growing unchecked across the creek’s watershed, clogging up creekside areas that would normally be open.

It can spread by its roots, so pieces that break off and float down river can take root and become whole plants, growing from pieces as small as a couple of inches, said Lisa Jennings, natural resources specialist with the Grandfather Restoration Project at the U.S. Forest Service. Not to mention it creates a large number of seeds that can spread by water, wind and birds, and the plant takes a strong hold wherever it sprouts.

“You really need an integrated, holistic approach to treating to really reduce the impact of the species,” Kauffman said. “You’ll never completely eradicate it, but you can keep it in check.”

The North Carolina Wildlife Resources Commission was awarded a grant last year for $5,000 from the N.C. Wildlife Habitat Foundation for efforts to eradicate knotweed on commission land. The commission matched that with $10,000, for a total of $15,000 going toward eradicating Japanese knotweed at Wilson Creek, said Scott Loftis, a watershed enhancement coordinator.

“The biggest problem is that it’s non-native. It’s invasive, meaning it really just takes over and overpowers the other beneficial vegetation that’s there,” Loftis said. “We’re trying to knock it back and give those natives a fighting chance.”

The project to eradicate the plant from the Wilson Creek watershed has a target completion year of 2017.

The alien plants have a number of complex, negative effects on the local habitat. As a perennial, each year it drops its leaves and dies back nearly all the way to its roots, and its leaf litter changes the chemistry of the streams, reducing the habitat quality for trout and other aquatic life, Jennings said.

It alters the hydrology, or water movement, of river systems as well, colonizing and stabilizing open rocky or sandy areas that should migrate, and elbowing out natural plants, which usually take much longer to establish themselves, said Andrew Kota, stewardship director at Foothills Conservancy of North Carolina.

And the more it impacts the local environment, the more it encourages its own growth, compounding the problem exponentially, said Gary Kauffman, a plant ecologist with the U.S. Forest Service.

Because the large populations of knotweed are clustered mostly within 25 feet of the waterways, those fighting the weed must be especially mindful of not causing more harm, especially from use of herbicides, which would just end up in the water.

The most effective treatment is to cut the stems, which grow to 6 feet or more, Kauffman said, let it re-sprout, and then spray the sprouts with the aquatic-approved Triclopyr 3A herbicide, Kauffman said.

When removing the plant, all stems and pieces must be bagged or burned or they could take root and grow again, Jennings said.

One of the main obstacles of eradicating the knotweed is private property, mainly in the middle section of the creek, a total of about 25 landowners, Jennings said.

All other properties can be cleared of the plant, but if it still survives on these private properties, it will continue to spread.

“It’s a tough, tough plant to deal with,” Loftis said. “It’s going to be an ongoing, multi-year effort to reduce the densities to a controllable level. That’s the biggest issue–just its resistance to many of the common practices of plant control.”

But Loftis said the most important thing for the public is to just be aware, that while it may look like it’d make a great addition to the front yard, another situation could sprout up just like the one from Bill Crump’s front yard.

The Wilson Creek Visitors Center is looking for volunteers to help cut back knotweed on its property. To volunteer or learn more, contact Glennys James at 828-759-0005.