APWQC Japanese Knotweed Control Project
Terrestrial invasive species such as knotweed are proliferating on Assembly Point particularly along Crossover Lane.
Japanese knotweed is an aggressive bamboo like plant. It can reach more than 10 feet in height and has bamboo-like stems. Its roots grow horizontally and once established they are extremely persistent making knotweed difficult to eradicate. If left unchecked, knotweed creates a solid mono-culture and degrades local habitat and biodiversity by driving out native plants and animals. It spreads rapidly, destroying the understory. It can take over a small forest such as Otyokwa. Japanese knotweed has already altered the character of Lake Champlain Basin’s riparian zones.
Otyokwa has been visited twice by the NYS DEC forest expert. He noted the existence of invasives such as knotweed, Asian bittersweet, bush honeysuckle, burning bush, barberry and grape vines. He advised to start with something which is manageable. Controlling terrestrial invasives is important in the words of the Lake George Land Conservancy, “Protecting the land, protects the Lake”.
There are three methods to eradicate knotweed; two are manual and one is chemical. Among the manual methods are digging out the knotweed roots which is difficult as they extend 6 feet down. The second method is cutting the stalks and matting the area which is less disruptive but it must be repeated from spring to fall for 2 to 3 consecutive years. Caution must be taken to avoid further spread of the plants during these two manual methods. The stalks and leaves that are cut should be separated from the root balls and killed by heat by laying them on pallets, called drying stacks, for open air composting. The third method is cutting the knotweed stalks and applying the chemical herbicide glyphosate better known as Roundup. For large areas of knotweed, Roundup can be sprayed on the leaves. Protective gear and clothing should be worn. If Roundup is sprayed, there is the added risk of contaminating nearby streams or other water bodies. It also might require a Certified Applicator.
The Highway Department of the Town of Queensbury has periodically cut knotweed along Lake Parkway and Crossover Lane. However, it has not undertaken any suppression techniques.
The Assembly Point Water Quality Coalition has undertaken a small demonstration project to suppress a knotweed patch at 188 Lake Parkway which was covering the septic mound of the Hogan Family. In the fall of 2024 APWQC volunteers cut the knotweed on and surrounding the Hogan septic mound and then covered a large area with an impermeable tarp and a small area with heavy rubber roofing mats. Suppression was effective. In removing the tarp/mats in the spring 2025, some small white stems emerged but had no light to thrive. These white stems were weed whacked and the tarp/mats replaced. This process was repeated from April to August 2025.
We performed continuous whacking around the interpretive sign in late May. Insert photo. Suppression by matting still was working well. Photos in the slide show demonstrate the effective suppression by the rubber roofing. Insert slide show. The conclusion is that suppression using dark tarps/mats is the best control. However, continuous weed-whacking is necessary to keep growth at bay.
The APWQC demonstration project is based on a Vermont knotweed control program in Lamoille County called KnotinHydePark. The program started in 2021 and consists of repeated cuttings so that knotweed rhizomes (roots) run out of gas using up energy for resprouting in response to cutting. Root masses and rhizomes are the promiscuous part of the plant but will die when stripped of any growth that sprouts out of them. Smothering with tarps or mats weakens the rhizomes and buys time in that it prevents knotweed patches from getting larger and allows for cutting whatever knotweed comes up around the edges of the material. At every project site there was a massive reduction of knotweed.
Japanese knotweed is an aggressive bamboo like plant. It can reach more than 10 feet in height and has bamboo-like stems. Its roots grow horizontally and once established they are extremely persistent making knotweed difficult to eradicate. If left unchecked, knotweed creates a solid mono-culture and degrades local habitat and biodiversity by driving out native plants and animals. It spreads rapidly, destroying the understory. It can take over a small forest such as Otyokwa. Japanese knotweed has already altered the character of Lake Champlain Basin’s riparian zones.
Otyokwa has been visited twice by the NYS DEC forest expert. He noted the existence of invasives such as knotweed, Asian bittersweet, bush honeysuckle, burning bush, barberry and grape vines. He advised to start with something which is manageable. Controlling terrestrial invasives is important in the words of the Lake George Land Conservancy, “Protecting the land, protects the Lake”.
There are three methods to eradicate knotweed; two are manual and one is chemical. Among the manual methods are digging out the knotweed roots which is difficult as they extend 6 feet down. The second method is cutting the stalks and matting the area which is less disruptive but it must be repeated from spring to fall for 2 to 3 consecutive years. Caution must be taken to avoid further spread of the plants during these two manual methods. The stalks and leaves that are cut should be separated from the root balls and killed by heat by laying them on pallets, called drying stacks, for open air composting. The third method is cutting the knotweed stalks and applying the chemical herbicide glyphosate better known as Roundup. For large areas of knotweed, Roundup can be sprayed on the leaves. Protective gear and clothing should be worn. If Roundup is sprayed, there is the added risk of contaminating nearby streams or other water bodies. It also might require a Certified Applicator.
The Highway Department of the Town of Queensbury has periodically cut knotweed along Lake Parkway and Crossover Lane. However, it has not undertaken any suppression techniques.
The Assembly Point Water Quality Coalition has undertaken a small demonstration project to suppress a knotweed patch at 188 Lake Parkway which was covering the septic mound of the Hogan Family. In the fall of 2024 APWQC volunteers cut the knotweed on and surrounding the Hogan septic mound and then covered a large area with an impermeable tarp and a small area with heavy rubber roofing mats. Suppression was effective. In removing the tarp/mats in the spring 2025, some small white stems emerged but had no light to thrive. These white stems were weed whacked and the tarp/mats replaced. This process was repeated from April to August 2025.
We performed continuous whacking around the interpretive sign in late May. Insert photo. Suppression by matting still was working well. Photos in the slide show demonstrate the effective suppression by the rubber roofing. Insert slide show. The conclusion is that suppression using dark tarps/mats is the best control. However, continuous weed-whacking is necessary to keep growth at bay.
The APWQC demonstration project is based on a Vermont knotweed control program in Lamoille County called KnotinHydePark. The program started in 2021 and consists of repeated cuttings so that knotweed rhizomes (roots) run out of gas using up energy for resprouting in response to cutting. Root masses and rhizomes are the promiscuous part of the plant but will die when stripped of any growth that sprouts out of them. Smothering with tarps or mats weakens the rhizomes and buys time in that it prevents knotweed patches from getting larger and allows for cutting whatever knotweed comes up around the edges of the material. At every project site there was a massive reduction of knotweed.
