Southeast Exotic Pest Plant Council Invasive Plant Manual
Common Name: Japanese Knotweed
Scientific Name: Polygonum cuspidatum (Sieb. & Zucc.)
Japanese knotweed, commonly known as crimson beauty, Mexican bamboo, Japanese fleece flower, or Reynoutria, was probably introduced to the U.S. as an ornamental. Initially useful for erosion control, as an ornamental, and for landscape screening, Japanese knotweed spreads quickly to form dense thickets that can alter natural ecosystems or interfere with landscaping. It is a semi-woody, bushy perennial and a member of the Polygonaceae (Knotweed) family.
Japanese knotweed can tolerate a variety of adverse conditions including full shade, high temperatures, high salinity, and drought. It is found near water sources, in low-lying areas, waste places, utility rights of way, and around old homesites. It can quickly become an invasive pest in natural areas after escaping from cultivated gardens. It poses a significant threat to riparian areas, where it can survive severe floods. It is rapidly colonizing scoured shores and islands.
Grubbing: This method is appropriate for small initial populations or environmentally sensitive areas where herbicides cannot be used. Using a pulaski or similar digging tool, remove the entire plant including all roots and runners. Juvenile plants can be hand-pulled depending on soil conditions and root development. Any portions of the root system not removed will potentially resprout. All plant parts, including mature fruit, should be bagged and disposed of in a trash dumpster to prevent reestablishment.
Cut Stump Treatment: Use this method in areas where vines are established within or around non-target plants or where vines have grown into the canopy. This treatment remains effective at low temperatures as long as the ground is not frozen.
Glyphosate: Cut the stem 5 cm (2 in) above ground level. Immediately apply a 25% solution of glyphosate and water to the cross-section of the stem. A subsequent foliar application of glyphosate may be required to control new seedlings and resprouts.
Triclopyr: Cut the stem 5 cm (2 in) above ground level. Immediately apply a 25% solution of triclopyr and water to the cross-section of the stem. A subsequent foliar application may be necessary to control new seedlings.
Foliar Spray Method: Use this method to control large populations. It may be necessary to precede foliar applications with stump treatments to reduce the risk of damaging non-target species.
Glyphosate: Apply a 2% solution of glyphosate and water to thoroughly wet all foliage. Do not apply so heavily that herbicide will drip off leaves. The ideal time to spray is after surrounding vegetation has become dormant (October-November) to avoid affecting non-target species. A 0.5% non-ionic surfactant is recommended in order to penetrate the leaf cuticle, and ambient air temperature should be above 65Â°F.
Triclopyr: Apply a 2% solution of triclopyr and water to thoroughly wet all foliage. Do not apply so heavily that herbicide will drip off leaves. The ideal time to spray is after surrounding vegetation has become dormant (October-November) to avoid affecting non-target species. A 0.5% non-ionic surfactant is recommended in order to penetrate the leaf cuticle, and ambient air temperature should be above 65Â°F.
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Steffey, J. The buckwheat family. American Horticultural Society 59(7):10-11; 1980.
Young, R. G.; Balogh, R. A.; Sitler, T. R.; Aharrah, E. C. An investigation of Japanese fleeceflower (Polygonum cuspidatum) planted on strip mines in Clarion and Venango counties, Pennsylvania. Proceedings 1982 Symposium on Surface Mining, Hydrology, Sedimentology, and Reclamation. Office of Engineering Services, University of Kentucky, 143-152; 1982.
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