Knotweed is a particularly dangerous invasive species, with the ability to smother and out-compete all other plants along riverways or roadways. Knotweed grows rapidly – 10 feet in a single growing season – and it can sprout from rhizomes or even small cuttings. This fantastic adaptability makes it a nightmare – an expensive nightmare – to eradicate once it is established. 

Knotweed is not just a danger to our local ecosystems – it directly affects human activities, from decreasing clean water, to worsening flooding due to eroded streambanks, to destroying recreational fishing and hiking – even growing through built infrastructure, house foundations, retaining walls, sidewalk pavement, culverts and bridge foundations. Its dense stands can rapidly pose visibility challenges along roadways. 

Knotweed’s impact on ecosystems is heartbreaking. It forms dense stands of green, bamboo like plants, that outcompete all other flora, leaving a wall of knotweed – a monoculture. The knotweed system then destabilizes streambanks, affecting local water quality and resulting in higher silt content. With reduced water quality, and elimination of native habitat or food sources, insect populations rapidly die down – and bring down the populations of fish, amphibians, reptiles, and all other aquatic and wetland dwellers.  

Because knotweed can so easily regenerate from even tiny cuttings (½ inch) or rhizomes, eradication of established patches is incredibly expensive. Rhizomes can spread at least 23 feet from the parent plant, and at least 6 feet deep. While it particularly loves wetlands and streams, it can also grow on dry soil – uncontrolled patches spread voraciously. 

The good news is that knotweed can be effectively targeted and controlled when it is first spotted. Early detection and reporting is crucial. Small populations can be dug up in their entirety, and when accompanied by systematic monitoring afterwards, can prevent a knotweed incursion entirely. Due to the nature of its rhizomatic spreading, larger populations are often most effectively controlled with targeted use of chemicals, such as stem injection. 

Targeting knotweed benefits numerous other environmental and infrastructure efforts. Knotweed removal directly provides habitat for native restoration – and, the careful and coordinated work needed to target knotweed makes it an excellent “partner” for other efforts, whether they are targeting other invasive species, restoring habitat or streambanks, or building a more climate-resilient infrastructure.