Efforts being made to eradicate Japanese knotweed

Contributed photoA patch of the invasive species Japanese knotweed in Niagara County. The Soil & Water Conservation District is working toward eradicating the fast-growing plant.


The Niagara County Soil & Water Conservation District is working toward eradicating the invasive species Japanese knotweed in Niagara County.

Japanese knotweed is a tall, shrubby, herbaceous perennial that forms dense patches that can reach heights of over 10 feet. The invasive plant was introduced into the U.S. from Eastern Asia in the late 1800s as an ornamental, and has become a very problematic plant. This plant spreads rapidly and forms dense populations that out-compete native vegetation which results in reduced species diversity, altered ecosystems and negatively impacted wildlife habitat.

Japanese knotweed grows aggressively in riparian and disturbed areas and can have detrimental effects on infrastructure. Due to a thick canopy, there is little to no vegetative ground cover in a knotweed patch and the exposed bare soil is susceptible to erosion which poses a threat to riparian areas.

Japanese knotweed has hollow, bamboo-like stems with purple speckles. The leaves are broad and rounded at the base, tapering to a sharply pointed tip. It can be easily identified in the fall from its small, white flower spikes that form on the mature plant. The bamboo like stems are very sturdy and will stand through the winter and have a brownish-red tint.

The Soil & Water Conservation District has received a Cooperative Weed Management Area grant through the Great Lakes Restoration Initiative to help eradicate the plant. Multiple patches of knotweed have been treated for several years in the Eighteenmile Creek watershed and the eradication program is being expanded throughout the county with this grant. Sites are being identified and prioritized for the eradication efforts.

The plant is very difficult to eradicate, and it will typically take several years to eliminate an entire patch.

During our eradication efforts, we have heard from numerous landowners that have been trying to eradicate the plant for years, with no success. Many have indicated that the patches are spreading very quickly. To keep the plant from spreading, it should not be cut and moved. A small piece of root or a stem fragment containing an internode can start a new plant if it contacts the soil.

A range of chemical control methods, used alone or in conjunction with cutting, have been proven effective on smaller infestations, including foliar spray, cut and wipe, and stem injection. Stem injection of glyphosate has proven to be the most effective method, but it is very labor intensive and time consuming.

Soil & Water Conservation District staff have located hundreds of sites across the county and looking to add to their inventory of sites in the county. Early detection, rapid response is the best way to control the plant, while the infestations are small. This summer their is a crew working on hundreds of sites around the county trying to control the plant with stem injections. If you know of any Japanese knotweed sites or would like some advice on eradicating the plant from your property, please call the Niagara County Soil & Water Conservation District at 434-4949, Ext. 4.


Dave Reckahn ia natural resource technician with the Niagara County Soil and Water Conservation District.

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