Identification: According to Winston et al. (2017): Habit: upright herbaceous perennial that grows 1–3 m tall
Stems/Roots: deep taproot and extensive rhizomes that may extend 7–20 m laterally. The stems are jointed at the nodes resembling bamboo and are hollow, smooth, and purplish turning green with age. The stems are often woody at their base.
Leaves: alternate, 8–15 cm long, and 5–12 cm wide with an abruptly pointed tip and a flat or tapering base
Flowers: small and creamy-white grown in branched clusters from leaf axils near stem ends. Flower clusters are 8–15 cm long.
Fruit/Seeds: papery, 3-winged, and 10 mm long
Ecology: Habitat: Idatori knotweed grows in a wide variety of habitats including riversides, swamp forests, disturbed forest edges, mountain slopes, sand dunes, and roadway edges, typically in disturbed areas (Beerling et al. 1994, Del Tredici 2017). Common dispersal corridors are along road, railway, and waterways (Barney 2006).
Life History: This species is an herbaceous perennial with an extensive woody rhizome system (Beerling et al. 1994). Idatori knotweed spreads from both seed dispersal and can regenerate from very small (40mm) pieces of stem or rhizome (De Waal 2001). These small pieces can be dispersed via flooding or cutting debris leading to new populations (Barney 2006). Flowering occurs in the late summer and fall (Child and Wade 2000).
Tolerances: Idatori knotweed grows in a wide variety of soils (Beerling et al. 1994) including acidic soils with a pH of less than 4 (Child and Wade 2000). In its native Japan, knotweed is one of the first species to colonize lava fields (Child and Wade 2000). Typically found in freshwater environments, Richards et al. (2008) have documented Idatori knotweed in salt marshes. This species is highly resilient in the face of repeated disturbance i.e., cutting or mowing (Del Tredici 2017).
Community Interactions: The nectar produced by the many flowers can serve as a late season source for bees and other pollinators (Child and Wade 2000).
References: (click for full references)
Barney, J.N. 2006. North American history of two invasive plant species: phytogeographic distribution, dispersal vectors, and multiple introductions. Biological Invasions 8:703–717.
Beerling, D.J., J.P. Bailey, and A.P. Conolly. 1994. Fallopia japonica (Houtt.) Ronse Decraene. Journal of Ecology 82:959–979.
Braatne, J.H., S.M.P. Sullivan, and E. Chamberlain. 2007. Leaf decomposition and stream macroinvertebrate colonisation of Japanese knotweed, and invasive plant species. International Review of Hydrobiology 92:656–665.
Chen, H., T. Tuck, X. Ji, X. Zhou, G. Kelly, A. Cuerrier, and J. Zhang. 2013. Quality assessment of Japanese knotweed (Fallopia japonica) grown on Prince Edward Island as source of resvertarol. Journal of Agricultural and Food Chemistry 61:6383–6392.
Child, L., and M. Wade. 2000. The Japanese knotweed manual: The management and control of an invasive alien weed. Packard Publishing Limited, West Sussex, UK.
Clements, D.R., T. Larsen, and J. Grenz. 2016. Knotweed management strategies in North America with the advent of widespread hybrid bohemian knotweed, regional differences, and the potential for biocontrol via the psyllid Aphalara itadori Shinji. Invasive Plant Science and Management 9:60–70.
De Waal, L.C. 2001. A viability study of Fallopia japonica stem tissue. Weed Research 41:447–460.
Del Tredici, P. 2017. The introduction of Japanese knotweed, Reynoutria japonica, into North America 1. The Journal of the Torrey Botanical Society 144(4):406–416.
Global Invasive Species Database. 2021. Species profile: Polygonum cuspidatum. Downloaded from http://www.iucngisd.org/gisd/species.php?sc=91 on 14-09-2021.
Maerz, J.C., B. Blossey, and V. Nuzzo. 2005. Green frogs show reduced foraging success in habitats invaded by Japanese knotweed. Biodiversity and Conservation 14:2901–2911.
Palmeri, J. and E. Kiviat. 2021. Toxic effects of knotweed Polygonum cuspidatum s.l. rhizome on the mosses Atrichum angustatum and Thuidium delicatulum. Lindbergia 44: linbg.01131.
Richards, C.L., R.L. Walls, J.P. Bailey, R. Parameswaran, T. George, and M. Pigliucci. 2008. Plasticity in salt tolerance traits allows for invasion of novel habitat by Japanese knotweed s.l. (Fallopia japonica and F. bohemica, Polygonaceae). American Journal of Botany 95(8):931–942.
Shaw, R.H., S. Bryner, and R. Tanner. 2009. The life history and host range of the Japanese knotweed psyllid, Aphalara itadori Shinji: Potentially the first classical biological weed control agent for the European Union. Biological Control 49:105–113.
United States Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS). 2021. Polygonum cuspidatum Siebold & Zucc. plant profile. https://plants.usda.gov/home/plantProfile?symbol=POCU6 (accessed 21 September 2021).
Vanderlklein, D.W., J. Galster, and R. Scherr. 2014. The impact of Japanese knotweed on stream baseflow. Ecohydrology 7:881–886.
Winston, R.L., C.B. Randall, B. Blossey, P.W. Tipping, E.C. Lake, and J. Hough-Goldstein. 2017. Field Guide for the Biological Control of Weeds in Eastern North America. USDA Forest Service, Forest Health Technology Enterprise Team, Morgantown, West Virginia, USA.
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.
