It spreads through its rhizomes in two ways: by sending out lateral shoots to create ever-larger stands, and by re-sprouting from rhizome fragments, creating new populations. The knotweed created a barrier that was approximately 6-8 feet high and virtually impenetrable. You must prevent Japanese knotweed on … After initial treatment, project managers realized that stem size on re-growth is not large enough for injection – the stem must be at least ½ inch in diameter – and therefore follow-up treatments require foliar application. The Spruce / Jordan Provost. Knotwood re-growth after first treatment. Total Time: 2 hrs. Despite the promise of the “Cut, Cut, Cut” method, this approach has not yet resulted in the complete eradication of knotweed. Therefore, the strategy is to use the most cost-effective treatment in the short term (herbicides) combined with planting for restoration. Along roadways and bike paths, knotweed causes safety concerns when it blocks signs, sight lines, and walkways. Overview. Chemical treatment is the only viable control. Although invasive plants abound in many areas of AGM, during the last six years the Friends have focused invasive management efforts in a test area along the Bikeway, about 100 yards in length, where a massive stand of knotweed, apparently introduced during construction of the bikeway, had grown up to block the view of the wetland from spring through fall. Treatment with systemic herbicide can be effective, but you might need to treat repeatedly; another possibility is stem injection or application of a systemic herbicide to freshly cut stems, though this is labor intensive. Biocontrols are species selected from an invasive species’ … Once control was underway, the project managers realized that restoration of Exit 14 would be necessary to repair the site and help with continued control of the knotweed. Label bottle. Be forewarned that this is a multi-year project (but the results will be worth it). In August 2009, with the end of the contract approaching, knotweed re-growth within the newly planted restoration was pulled and spot-sprayed. In wetlands, only apply herbicides registered for use in those areas. The first, referred to as “Cut, Dig and Cover” or “Dig, Dig, Dig,” has involved cutting the stalks, digging out the root crowns and as much of the rhizome network as possible, and then covering the ground with black landscape plastic for an extended period of time in an effort to block sunlight and thereby destroy any remaining rhizomes. Humans not only spread knotweed by moving rhizomes from place to place, but our management practices may also be causing infestations to expand more rapidly. Let cut canes of Japanese knotweed dry out for a week or so, then burn them in a controlled setting such as a fire pit. Since 2005, the Friends have used two experimental techniques in an attempt to eliminate knotweed from this area. You can take organic weed-control measures to deal with Japanese knotweed to some degree (such as choking it out with tarps), but you have a better chance of getting rid of this menace if you compromise and supplement such efforts with the occasional use of an herbicide. The local control and eradication of an invasive species, however, is achievable with adequate aftercare and re-establishment of a native plant community. The problem: The garden is still battling Japanese knotweed, an invasive species that grows quickly and is difficult to get rid of. We certainly can’t address all invasive plant populations in this way, nor, given the persistence of invasive plants, can we necessarily expect these designed landscapes to last any longer than a garden once the maintenance stops. Sites chosen for knotweed injection included recently planted areas and a large stand of approximately 5000 square feet located at Exit 14 off of I-290 in Worcester, MA. Estimated Cost: $0 to 25. Every year, the Parks Division and contract crews remove non-native invasive plants such as Japanese knotweed, garlic mustard, black swallow-wort, glossy buckthorn and tree of heaven from public open spaces. This field is for validation purposes and should be left unchanged. It was used as an ornamental plant on properties and also for erosion control due to its deep and interwoven root system. Six-inch sprays of tiny, greenish-white flowers sprout from leaf axils in mid-summer, followed in autumn by a profusion of dangling, triangular, winged nut-like seeds as the foliage turns yellow. With the large stand at Exit 14, in comparison to the foliar spray, stem injection appeared to be more effective in preventing re-growth (both fewer plants and weaker growth). These have included repeated cutting, mulching, application of herbicide to freshly cut stems, and application of herbicide as a foliar spray. The results that the Friends have achieved in AGM demonstrate that knotweed can successfully be controlled, weakened, and possibly even eliminated, without the use of herbicides. Once introduced to a site, knotweed easily out-competes other vegetation to create extensive mono-stands, altering native or otherwise stable vegetative communities and habitat. The “Cut, Cut, Cut” method, which requires less exhausting up-front work but more continuous effort over the years, has offered better promise. Soll, Jonathan, The Nature Conservancy: Controlling Knotweed in the Pacific Northwest, 2004. Minimal control of knotweed by pulling and spot treatment (depending on availability of applicator) is planned for another two years by which time the switchgrass should be dense and well-established. 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