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Here's a transcript of the story published September 20, 2024 in CT Insider by Staff Writer Abby Weiss:
As a life-long gardener, Dawn Handschuh understands the value of preserving native plants in her neighborhood. Brought to the U.S. from Japan in the 1800s, Japanese knotweed is a rapidly spreading invasive, non-native plant that grows in dense thickets of vegetation, crowding out surrounding native species and creating a monoculture in the areas it resides. Its sturdy and extensive root system can also exacerbate erosion, especially during floods, Handschuh said. “It reduces the richness of our biodiversity and it suppresses the growth of other herbaceous plants. It affects water quality when it's growing along these rivers and wetland areas, and it does increase flood risks,” she said. Handschuh and other members of the Newtown Knotweed Initiative, which formed in 2023, are raising awareness about the threat of Japanese knotweed in their local area and provide advice on how to manage it. Newtown residents have reported sightings of the plant in Dickinson Park, Fairfield Hills and along the Pootatuck River, according to the NKI website. Late August and September mark flowering season for the perennial shrub, sprouting small white petals in elongated clusters. But, despite its flowery appearance, the bamboo-like species is wreaking havoc in parts of the U.S., with the potential to threaten property values. Also known as Itadori knotweed, the species grows anywhere with disturbed soil, including along roadways and watery areas, and can reach a height of 15 feet tall, with two thirds of its mass underground. It can crack through pavement and withstand extreme weather events, including severe droughts and floods, according to the University of Connecticut. “It’s very problematic for everybody, whether it's landowners of large tracts of land or homeowners with small tracts of land,” Victoria Wallace, an extension educator at the University of Connecticut, said. “It can do a lot of damage to foundations and to roadways.” Dr. Jatinder Aulakh, an associate weed specialist at the Connecticut Agricultural Experiment Station, can’t say for certain whether the plant has been spreading in Connecticut, but reports to the Connecticut Invasive Plant Working Group, which exchanges information on invasive plants in the state, have gradually risen throughout recent years due to growing public awareness and interest, he said. The plant also spreads rapidly during warm seasons, mainly due to human activity, Aulaukh said. People can leave root and stem fragments on their properties and roadside maintenance or construction crews can spread these fragments when working on an infested area, he said. The Connecticut Agricultural Experiment Station lists it among the top 10 invasive plant species in the state with management options, and it’s illegal to import it in the state. It is also costly and a tenuous struggle to eradicate, which can decrease the values of infested properties, he said. It can take three to five years to manage the plant with herbicides, he said, and can cost $1,000-2,000 per year. Another cause for the reduced property values is that its rhizomes (stems) can also penetrate under concrete and into somebody’s basement, he said. He’s heard reports of residents buying homes in the winter and discovering the plant on their property in the spring or summer. “And they were regretting it after,” he said. “If somebody knows it is Japanese knotweed, they are definitely not going to be paying the competitive price for their property.” In the United Kingdom, where Japanese knotweed has become one of the most invasive and destructive plants, property owners must disclose knotweed infestations if they’re selling. They can also take out insurance to cover its treatment, according to The Wall Street Journal. How to deal with Japanese knotweed There are various ways homeowners can mitigate or eradicate the spread of Japanese knotweed. The first is to hire a landscaper to remove it fully; don’t dig it up yourself. Scientists at the University of Connecticut recommend cutting the plants three times a year before flowering season or spraying them with a glyphosate-based herbicide during the off-flowering season. Spraying herbicides during flowering season can threaten pollinators. Some experts recommend the product Roundup. However, the safety of glyphosate has been a subject of international debate. The World Health Organization found that the herbicide is “probably carcinogenic,” while the U.S. Environmental Protection Agency insists that’s unlikely. If people don't want to use glyphosate, they can try a herbicide called Triclopyr, which is costlier but equally as effective, Aulaukh said. The Department of Environmental Conservation at the University of Massachusetts Amherst also received permission in 2020 to release a non-native bug called Aphalara itadori. It’s currently the only biological control agent approved for knotweed and scientists are still testing this method. The best method for tackling the spread of Japanese knotweed is to use an integrated approach: cut the plant to the ground in June, letting it grow a little more and spray it with herbicide in late September or early October, Aulaukh said. Multiple Connecticut towns have adopted this approach, he said. Towns like Glastonbury and Stamford have developed plans in recent years to crack down on the species. “But again, it's a multi-year project. You need to be doing those treatments for at least three years, sometimes five years, and then you need to plant some native vegetation in the area to make sure it's 100 percent under control. So it's intensive,” he said. |
