Know (and tame) your knotweed

| June 30, 2021

The speakers: in the blue shirt, arms crossed, Jeff Skelding, executive director of the Friends of the Upper Delaware; next to him in the red hat, Steven Schwartz, heading up the knotweed project for FUDR. PHOTO BY MEG MCGUIRE
The speakers: in the blue shirt, arms crossed, Jeff Skelding, executive director of the Friends of the Upper Delaware; next to him in the red hat, Steven Schwartz, heading up the knotweed project for FUDR. PHOTO BY MEG MCGUIRE

Gathered on the banks of the East Branch of the Delaware River, they all had their stories to tell of an ongoing battle with knotweed, which on this sunny Saturday morning grew tall enough to blot out any view of the river, not more than 50 feet away.

“Knotweed has taken away my joy,” said Valerie Rodgers-Garcia, who owns riverfront property in Hancock, N.Y.

About 25 people are here, hoping that Steven Schwartz, who’s heading up the Friends of the Upper Delaware knotweed project, will have the best way to rid their properties of the three varieties found locally: Giant Knotweed, Bohemian Knotweed and Japanese Knotweed.

What is this pesky plant? Well, for starters, it’s invasive, having come from somewhere in Asia, likely in the 1800s when it was imported for its ability to flourish in gardens.

And everywhere else, it seems. 

Though it clearly thrives on riverbanks, obscuring views of and access to rivers and streams, it seems happy enough to grow anywhere, especially on recently disturbed land. In addition to its height (some varieties up to 16 feet), it can crowd out native plants that are better at stabilizing the riverbanks.

Not a short guy, Brett Lorenzen, from the Friends of the Upper River, is dwarfed by knotweed. PHOTO BY MEG MCGUIRE

Eric Burkhart, a botanist from Pennsylvania State University, who is a partner with Schwartz in this knotweed project confirmed that knotweed grows all over Pennsylvania, though different species tend to be a problem in different areas. In central Pennsylvania, it’s mostly Giant Knotweed. Here in the Delaware River watershed it’s mostly Japanese knotweed as well as the hybrid. 

All the varieties are champion propagators using pollination, as well as side shoots that come out underground from the central rhizome. And the real difficulty is that, just as might think you’re getting rid of it, as stalks break off, they can be carried in water downstream and re-root to produce more plants. This is a special problem after flooding, when they can be carried far and are happy to root in the silt deposited as flood waters recede.

They occupy riverbanks but don’t help it: Instead of dying down on the ground as most small plants do to overwinter, the stalks stand upright and barren, so it increases the sediment that can pour into the river with heavy rainfalls.

It has earned itself a place on the list “100 of the World’s Worst Invasive Species,” put out by the International Union for Conservation of Nature. It shares this dubious distinction with the common malaria mosquito and another pest of the Delaware River watershed, the zebra mussel.

As always, the views in the Upper Delaware are terrific, but the fierce hedge in the middle, on the left, is knotweed. PHOTO BY MEG MCGUIRE

And there’s this from Wikipedia: The invasive root system and strong growth can damage concrete foundations, buildings, flood defenses, roads, paving, retaining walls and architectural sites.

At the base of the plant is its rhizome, which sends out significant runners many feet long to reproduce but neither is deeply rooted, which is part of the reason it’s not great for holding soil in place, explained Jessica Newbern, a biologist with the National Park Service, a partner with FUDR on this knotweed project.

Jessica Newbern, a biologist with the National Park Service, explains the different types of knotweed to Valerie Rodgers-Garcia. PHOTO BY MEG MCGUIRE

It’s funded with a federal Delaware Watershed Conservation Fund grant in partnership with the NPS, and the National Fish and Wildlife Service, the New York League of Conservation Voters, Stroud Research Center and Shippensburg University. The overarching goal is to educate the public (that’s today’s gathering) and to better understand the impact of the spread of knotweed in the Upper Delaware River watershed. 

But back to the grassroots of knotweed eradication: people. 

Both Jeff Skelding, the executive director of the Friends of the Upper Delaware, and Schwartz emphasized the crucial part that landowners play in reducing and even eradicating this weed. But they also said it was important to join forces with neighbors, since if you get rid of it on your property it can easily grow back from a neighbor’s land.

It is tenacious. The people gathered here in Firemen’s Field in Hancock, N.Y., wanted to know how to get rid of it. And if you’re like them, and have a knotweed problem, check out this link at the FUDR site. It lists the various ways that you can use, from constant cutting, to careful use of herbicide to what was certainly the most favored from the list: goats.

Yep. Goats love to nosh on knotweed. Today’s goats were from Grant’s Goats, run by Terry Grant. One of the participants, Tim Greenberg, asked if it was possible to rent a goat, and there was a murmur of interest from the rest of the audience.

And Grant said he’d be interested, but pointed out that if you were to have a goat to eat your knotweed, you better set up a chair near the plants to keep the goats happy — apparently they like people! And keep them fenced in, because they’ll eat everything.

There’s another demonstration and talk on July 17, 11 a.m. to 2 p.m. at Will Smith Memorial Park, Deposit, N.Y.

You can write with questions to knotweed@fudr.org

And Rodgers-Garcia gave a thumbs up to the talk: “There is hope!”

Terry Grant, owner of Grant’s Goats, places a kid next to its mother in the experimental patch using goats to graze on — and hopefully eradicate — knotweed. PHOTO BY MEG MCGUIRE

And this just in from the Brodhead Watershed Association, based in Stroudsburg, Pa.

Brodhead Watershed Association will host a workshop in July on how to control knotweed along creeks — and in your backyard.

Register for a live, on-stream workshop led by Robin Anglemyer. Learn the right time to cut knotweed, what tools you need, how low to cut it  (hint: ankle height is too low!), and what to do next. 

The tentative date is Wednesday, July 7, at 4 p.m. — but exact timing of the workshop will depend on weather conditions and knotweed growth. 

Register now to get detailed updates.

Go to https://brodheadwatershed.org/greening-mountainhome for more information about the knotweed removal project.

Meg McGuire

Meg McGuire

Meg McGuire has been a journalist for 30 years in New York and Connecticut. She started in weekly newspapers and moved to full-time work in dailies 25 years ago. She knows about the tectonic changes in journalism firsthand, having been part of what was euphemistically called a "reduction in force" six years ago. Now she's working to find new ways to "do" the news as an independent online publisher of news about the Delaware River, its watershed and its people.

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