Japanese Knotweed in the Beaverkill

  CRISP Campground Steward Intern, Evan Sweeney (left), with the Excelsior Conservation Corps during their third hitch last week in the Beaverkill.

 CRISP Campground Steward Intern, Evan Sweeney (left), with the Excelsior Conservation Corps during their third hitch last week in the Beaverkill.

Catskill Center's Catskill Regional Invasive Species (CRISP) staff recently met with Friends of the Beaverkill to discuss the spread of Japanese Knotweed in the region. The Friends of Beaverkill Community is a New York State not-for-profit corporation primarily dedicated to preservation and welfare of the Beaverkill Community, initially the picnic area of the Campsite, the Beaverkill Church, the Covered Bridge, and the Iron Bridge. 

Japanese Knotweed (Reynoutria japonica var. japonica)

   CRISP Campground Steward Intern, Evan Sweeney (right), with the Excelsior Conservation Corps during their third hitch last week in the Beaverkill.

 CRISP Campground Steward Intern, Evan Sweeney (right), with the Excelsior Conservation Corps during their third hitch last week in the Beaverkill.

This common streamside and roadside invader can reproduce from the tiniest root fragment and a new plant can grow out of a single leaf. The stems are hollow and the large, heart-shaped leaves grow alternatively from stems.  Japanese knotweed has been expanding along many Catskill rivers and streams. Japanese knotweed displaces native vegetation due to its aggressive growth and by forming dense stands that shade out other plants; it lowers quality of habitat for fish and wildlife; and can contribute to streambank erosion problems. Japanese knotweed exceedingly difficult to manage as any disturbance can lead to its spread and control can take many years due to the energy storage capacity of its rhizomes.

At the Beaverkill Campground a combination of the “fold-over” and chemical control methods were used.  An effort was made to minimize the chances of vegetative spread. Folding the knotweed at its first leaf has been found to be effective in conjunction with herbicide spraying for control.  The Catskill Regional Invasive Species Partnership (CRISP) is currently mapping Japanese knotweed along the Beaverkill, especially upstream from the Beaverkill Campground.  If you have Japanese knotweed on your property, please contact John Thompson, CRISP Coordinator, email: jthompson@catskillcenter.org or phone (845) 586-2611 x103.  We’ll be happy to visit your property to expand our knotweed mapping project. Knotweed patches will be mapped by GPS and we will subsequently use that information to develop a management strategy for the Beaverkill.  Additional information on the CRISP program can be found here http://catskillcenter.org/crisp/

General information on knotweed control:

  • Only use manual control methods (e.g. mowing) if you can commit to doing it multiple times per season, at least two times per month in the growing season for at least three years. All parts of the plant should be collected and disposed of safely- Plant parts can re-sprout so do not allow them to spread to new areas. If you do mow a patch of the plant, you should clean equipment before you use the equipment outside of the knotweed patch so that you do not spread plant parts.
  • Herbicide control has been found to be effective.  Ideally spray in late August to September after plant is in flower.
  • To add to control efficacy or plants grow too tall to spray without a lot of overspray, bend the stalks down three to four weeks prior to when you expect to spray and then spray the regrowth.
  • Whatever control method you use, this will be a long-term project. Plan to continue controlling the knotweed plants continually for at least a few years for full control with follow-up yearly monitoring for a three more years thereafter, searching for new growth. One year of control is not fully effective so do not give up after one year of control.