Herkimer County Soil & Water Conservation
What to Do if You See Japanese Knotweed:
Use this website to try to make a positive identification. Many plants look similar to Japanese Knotweed.
Entire plant, stem, leaves, flower, seed. High resolution preferred. We’ll need them to confirm identification.
Call our office:315-866-2520 Ext. 5
Our Project Description & Outcome
Herkimer County Soil and Water Conservation District is involved in a multiyear invasive species project to inventory and eradicate high priority areas of Japanese Knotweed.
Phases 1 & 2 - 2016 & 2017
In 2016 we began the project by documenting all infested sites in the southern portion of our county. Infested sites were documented with photos, a description of the size and area, and other valuable information. The second phase was completed in 2017. We documented all infested sites in the northern portion of our county in the same way as phase 1.
Phase 3 - 2018 to Present
Phase three began in 2018 to determine the necessary steps to treat the high priority areas of Knotweed infestation. 2 staff members became certified pesticide technicians, and were able to begin treatment of high priority sites approved by our Board of Directors in 2019. Sites are prioritized based on natural resource concerns and level of maintenance issues affecting roads and culverts, as well as through our partnership with the Herkimer County Highway Department. Those staff members were upgraded to certified pesticide applicators in 2021. We have now had 3 years of treating some stands of knotweed, and nearly fully eradicated some infestations. Photos of a successful treatment adjacent to a priority waterbody can be found on the right.
The ultimate goal is to eradicate all high priority sites within the county thus promoting native species growth.
Identifying Japanese Knotweed
It is a rhizomatous (produces underground stems) perennial plant with distinctive, branching, hollow, bamboo-like stems, covered in purple speckles and can grow from 3-15 feet tall.
The leaves of the mature plant are 3 to 6 inches in length with a flat base and pointed tip. They are arranged on arching stems in a zig-zag pattern.
The plant flowers in late summer, August to September, with small creamy-white flowers hanging in clusters from the leaf axils (point at which the leaf joins with the stem).
The underground rhizomes are thick and woody with a knotty appearance and when broken reveal a bright orange-colored center. The horizontal roots can reach lengths of 65 feet or more.
The plant develops small winged fruit seeds which are triangular, shiny, and very small (about 1/10 inch long). Japanese Knotweed spreads primarily by seed (transported by wind, water, animals, and humans).
Herkimer County Invasive Species Project: Japanese Knotweed Inventory
What is Knotweed?
Japanese Knotweed is a robust, bamboo-like perennial plant native to Asia. Common names include Mexican or Japanese bamboo, elephant ear and fleece flower. It is a noxious weed that is fast growing and extremely aggressive. It invades along rivers and roads, but is also found in backyards, forests, parks, and farms.
Why is it a problem?
Knotweed spreads rapidly, forming dense thickets that overwhelms and shades out native vegetation. This threatens the diversity of our natural ecosystem, reduces species diversity, and negatively impacts wildlife habitat.
Limits recreational access and obstructing scenic views.
Because the ground under knotweed tends to have very little other growth, it can create bank erosion problems, clog small waterways and trout streams. It reduces food sources for wildlife and lower nutrient input into streams systems.
The aggressive growth of the Knotweed can also damage yards and structures such as foundation and roads.