Soil or plant material contaminated with non-native and invasive plants like Japanese knotweed can cause … … To learn more about Japanese knotweed and its control, check out Preventing the Spread of Japanese Knotweed, a guide created by the NH Department of Agriculture. Japanese knotweed, whose propagation is so notorious that it often has to be removed by pesticides or smothering the ground, not only kills native species along New Hampshire’s rivers but blocks access … Japanese Knotweed control and eradication in Hampshire and Japanese Knotweed management and removal in Southampton. seacoastonline.com ~ 111 New Hampshire Ave., Portsmouth, NH 03801 ~ Do Not Sell My Personal Information ~ Cookie Policy ~ Do Not Sell My Personal Information ~ Privacy Policy ~ Terms Of Service ~ Your California Privacy Rights / Privacy Policy. Conservation Practice Job Sheet NH-595 . Japanese knotweed is on the New Hampshire Prohibited Species List, making it illegal to transport, buy, sell, import or export. Many people mistake Japanese knotweed for bamboo, as the stems are jointed and hollow. Department of Agriculture, Markets & Food . By Paolo Martini on 2nd July 2019 (updated: 18th November 2020) in News. Hammer described the plant's root system as "aggressive," growing horizontally, up to 60 feet long, making it the most damage-causing part of the plant. Small populations can be controlled by continually cutting the canes and digging up the roots. Japanese knotweed ( Reynoutria japonica) is one of the most noxious invasive plants in the northeast. Japanese Knotweed – Polygonum cuspidatum . It can grow as much as eight inches a day in the … The State of New Hampshire passed the Invasive Species Act, which makes it illegal to “collect, transport, import, export, move, buy, sell, propagate, or transplant any living or viable portion of any plant species, which includes all of their cultivars and varieties, listed on the New Hampshire … Jeff Taylor makes an herbicide application to Japanese knotweed at the Mink Brook Nature Preserve in New Hampshire. UNH Cooperative Extension Master Gardener volunteers share information about home, yard, and garden topics with the people of New Hampshire. Knotweed should not be mowed, as mowing can result in spread. Under the right conditions mowed or cut stem fragments can root at the nodes. Japanese knotweed is a dense shrub that can grow up to 10 feet in height. The other, he said, is to dig it all up, dry it on a tarp, then burn or dispose of it. It’s found in every state except North Dakota, Nevada, Arizona, New Mexico, Texas, Florida and Hawaii. One of the most invasive weeds in the world, Japanese knotweed is native to Asia, where it is regarded as having medicinal value. Japanese knotweed growing at the bottom of a garden in Hampshire Japanese knotweed is commonly found throughout Hampshire and The Knotweed Company covers the whole area, including Portsmouth, Southampton, Winchester, Andover, Basingstoke, Farnborough, Aldershot, the New … Hammer has been studying effects of invasive species on "riparian forests," that grow next to water bodies. The stems of the plant are green with red spots further down; the plants can grow up to 3m tall. It should never be composted. Digital access or digital and print delivery. To rid a property of knotweed, Hammer said, there are three options. 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