Feds, County Take on Japanese Knotweed

As he mounted his all-terrain quad, a tank of herbicide secured to the back, Eric Schrading prepared to battle yet again in one of Union County’s parks.

But after years of combating Japanese Knotweed and several other invasive plant species spreading throughout Lenape Park, he knows this war will never end. With his help, the county has gained the upper hand, but this is one war that will never be totally won, he said. 

It’s not just a matter of invasive species like Japanese Knotweed crowding out native plant species. The monoculture that results reduces the diversity of wildlife that depend on the variety of other species of plant life to survive, said Schrading, an assistant supervisor with the U.S. Fish and Wildlife Service.

In 2001, the Union County Board of Freeholders agreed that the county would benefit from partnering with the Fish and Wildlife service, joining together on a project to protect nearly 20,000 native plants that were placed in a newly created wetlands park in Rahway.

Four years ago, the county agreed to the program at Lenape Park, which straddles portions of Westfield, Cranford and Kenilworth. As part of the program, Fish and Wildlife would spray the herbicides for three to four years. The Board of Freeholders, for its part, committed the county to continue planting native species supplied by Fish and Wildlife and maintain the targeted areas for at least 10 years.  

There are similar programs scattered around the state, although the worst problems with Japanese Knotweed are in Union and Essex counties, Schrading said. In a number of southern counties, where there are marshlands and other areas with brackish water, he sprays the herbicide to combat phragmites, although the spread of phragmites in the Passaic River Parkway required spraying in Berkeley Heights.

“The idea is not to eradicate all invasive plants—it’s probably not even possible—but to give native species a fighting chance,” Schrading said.

Before Schrading came in with his spraying equipment years ago, work crews went through the woods in Lenape Park cutting the Japanese Knotweed, which can grow upwards of 15 feet in height. The cutting not only weakens the plant, but makes it easier to apply the herbicide, which contains glyphosate, which only effects plant cells and presents no toxicity problems for insects or animals, he said.

“At this time of year, plants are going into dormancy, so they draw the chemical down into the roots,” Schrading said.

While there are varying theories as to how Japanese Knotweed was introduced to the Union-Essex area, it was initially thought of as an ornamental plant. In fact, the Olmsted landscape architectural firm, which designed the Union and Essex County park systems, along with Central Park in New York City and a myriad of other parks, included Japanese Knotweed in some of its planting designs. But no one knew then the consequence of their choice, Schrading said.

Riding his quad through the park one recent afternoon, Schrading said he expected he could spray most of the Japanese Knotweed in about three hours. He would refill the 15-gallon tank two more times before he was done. 

It was a far cry from his first visit when he brought in Fish and Wildlife’s big guns, an amphibious tank-shaped vehicle called the “Marsh Master” equipped with a 100-gallon tank filled with herbicide. It took two days to spray everything, he said.

Schrading estimates that in the treated area, the Japanese Knotweed was reduced by nearly 70 percent. Now much of the responsibility for holding the line will fall to the county, he said.