Homeowners: Please share this information with your licensed herbicide professional to create a treatment plan that we believe is the most effective method for controlling Japanese knotweed.
Legal Disclaimer and Safety Warning
The information provided on this website is for general educational and informational purposes only. Newtown Knotweed Initiative is a volunteer group and does not providing professional landscaping, agricultural or chemical consultation services.
The management of Japanese knotweed and other invasive species involving chemical herbicides carries inherent risks of physical injury, chemical exposure and environmental damage. Any reliance you place on the information found on this website is strictly at your own risk.
Late summer through early fall is prime time for managing Japanese knotweed with herbicide.
If you've followed us for a while, you know that cutting knotweed is not recommended and will make things worse. To assist Newtown residents who have begun the herbicide treatment protocol, Newtown Knotweed Initiative is making signage like this one available to homeowners who wish to alert town mowers not to mow their knotweed site. To request a sign, email a photo of your knotweed to [email protected]. Please do not request a sign if you don't plan to treat your knotweed infestation with herbicide in the September to October window, or if you are but your knotweed is not fronting the road. These signs were specifically created to alert Newtown DPW mowers to the presence of knotweed so that it is is not inadvertently mowed. Thank you for your cooperation. |
Due to knotweed's aggressive nature and ability to easily reroot, NKI does not recommend mowing or digging as a containment measure. Mowing also creates the risk of inadvertently spreading infestations via small bits of knotweed stems or roots caught in mower blades. For this reason, professional, licensed applicators with specific experience treating knotweed infestations will recommend a foliar herbicide treatment.
FOLIAR HERBICIDE TREATMENT Effective knotweed control is a multi-year endeavor, and repeat sprayings will be needed once a year for at least three years. As a reminder, knotweed should not be cut back unless you plan to treat it with herbicide that season, as cutting it alone will only encourage its growth. More information can be found here. WHEN Timing for controlling knotweed is key. Spraying should be delayed until after knotweed blooms to protect pollinating insects, typically from September through October. This is also the time when carbohydrates start flowing back down to the root system as the plant prepares to overwinter, making treatment most effective as the herbicide is also drawn into the rhizomes (root system). No further treatment should be done after the first frost occurs or once the leaves look wilted and brown. |
HOW
Given the complexities of using the right herbicide diluted to the appropriate strength at the right time, Newtown Knotweed Initiative strongly recommends that property owners hire a licensed professional. NKI recommends the following:
Michael Switser Connecticut licensed applicator North Country Landscape Management (203) 953-6325 "Our knotweed control protocol utilizes a strategic two-phase fall application of herbicide. Because the window for effective treatment is narrow, applying two targeted sprays during this fall translocation period maximizes systemic herbicide absorption, driving the product directly into the root system when the plant draws energy downward before winter dormancy." --- Mike Switser |
