Japanese Knotweed | National Invasive Species Information Center

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Japanese knotweed, foliage - Photo by Jack Ranney; University of Tennessee

Scientific Name:

Fallopia japonica (Houtt.) Ronse Decr. (ITIS)

Synonym:

Polygonum cuspidatum Siebold & Zucc.; Reynoutria japonica Houtt.

Common Name:

Japanese knotweed, fleeceflower, Mexican bamboo, huzhang

Native To:

Asia (Stone 2010)

Date of U.S. Introduction:

Late 1800s (Stone 2010)

Means of Introduction:

Introduced as an ornamental (Stone 2010)

Impact:

Crowds out native species (Stone 2010)

Spotlights

APHIS Issues Final Environmental Assessment for Biological Control of Japanese, Giant, and Bohemian Knotweeds (Nov 30, 2020)

USDA. Animal and Plant Health Inspection Service.

The U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS) has issued the final environmental assessment (EA) for releasing Japanese knotweed psyllid (Aphalara itadori) to manage Japanese, giant, and bohemian knotweeds (Fallopia japonica, F. sachalinensis, and their hybrid, F. x bohemica). After careful analysis, APHIS has determined that releasing Japanese knotweed psyllid within the continental United States is not likely to have a significant impact on the environment. Based on this determination, APHIS will not prepare an environmental impact statement and will begin issuing permits for the release of Japanese knotweed psyllid.

Distribution / Maps / Survey Status

Early Detection & Distribution Mapping System (EDDMapS) - Japanese Knotweed

University of Georgia. Center for Invasive Species and Ecosystem Health.

Provides state, county, point and GIS data. Maps can be downloaded and shared.

Images

Google Images - Japanese Knotweed

Google.

Invasive.org - Japanese Knotweed

University of Georgia. Center for Invasive Species and Ecosystem Health.

Videos

YouTube - Japanese Knotweed

Google. YouTube; University Nebraska - Lincoln. Extension.

Selected Resources

The section below contains highly relevant resources for this species, organized by source. Or, to display all related content view all resources for Japanese Knotweed.

Council or Task Force

Invasive Plants of Ohio: Fact Sheet 10 - Japanese Knotweed (PDF | 254 KB)

Ohio Invasive Plants Council.

See also: Invasive Plants of Ohio for worst invasive plant species identified in Ohio's natural areas

Priority Species: Japanese Knotweed

Washington State Recreation and Conservation Office. Washington Invasive Species Council.

Southeast Exotic Pest Plant Council Invasive Plant Manual - Japanese Knotweed

Southeast Exotic Pest Plant Council.

Partnership

Alaska Exotic Plants Information Clearinghouse (AKEPIC): Species Biography - Japanese Knotweed, Giant Knotweed, Bohemian Knotweed (Feb 7, 2011) (PDF | 304 KB)

University of Alaska - Anchorage. Alaska Center for Conservation Science.

See also: Non-Native Plant Species List for additional factsheets (species biographies) and species risk assessment reports of non-native species present in Alaska and also non-native species currently not recorded in Alaska (potential invasives)

Global Invasive Species Database - Fallopia japonica (herb, shrub)

IUCN. Species Survival Commission. Invasive Species Specialist Group.

Invaders Factsheet: Japanese Knotweed

Ontario's Invading Species Awareness Program (Canada).

Invasive Plant Atlas of the United States - Japanese Knotweed

University of Georgia. Center for Invasive Species and Ecosystem Health.

Invasive Species Compendium - Fallopia japonica

CAB International.

Japanese Knotweed Alliance

CABI Bioscience.

New York Invasive Species Information - Japanese Knotweed

New York Invasive Species Clearinghouse.

Non-native Species Information: Japanese Knotweed

Great Britain Non-Native Species Secretariat.

Weeds Australia - Japanese Knotweed (Fallopia japonica)

Centre for Invasive Species Solutions; Atlas of Living Australia; Australian Government. Department of Agriculture, Water and the Environment.

Federal Government

Fire Effects Information System (FEIS) - Polygonum sachalinense, P. cuspidatum, P. × bohemicum

USDA. FS. Rocky Mountain Research Station. Fire Sciences Laboratory.

National Exotic Marine and Estuarine Species Information System (NEMESIS): Chesapeake Bay Introduced Species Database - Polygonum cuspidatum

Smithsonian Institution. Smithsonian Environmental Research Center. Marine Invasions Research Lab.

PLANTS Database - Japanese Knotweed

USDA. NRCS. National Plant Data Center.

U.S. National Plant Germplasm System - Reynoutria japonica

USDA. ARS. National Genetic Resources Program. GRIN-Global.

International Government

Invasive Plants - Japanese Knotweed

Cornwall County Council (United Kingdom).

State and Local Government

Fact Sheet: Japanese Knotweed (Polygonum cuspidatum) (2014) (PDF | 237 KB)

New Hampshire Department of Agriculture, Markets, and Food. Division of Plant Industry.

See also: New Hampshire's Prohibited Invasive Plant Fact Sheets for additional invasive trees, shrubs, vines, and herbaceous plants

Invasive Species Best Control Practices - Japanese Knotweed (2012) (PDF | 373 KB)

Michigan Department of Natural Resource; Michigan State University Extension. Michigan Natural Features Inventory.

See also: Best Control Practice Guides for more guides

Invasive Plant Species Fact Sheet: Japanese Knotweed (2006) (PDF | 734 KB)

Indiana Department of Natural Resources. Invasive Plant Species Assessment Working Group.

See also: Species Assessments and Invasive Species for exotic animal and plant pests invading Indiana, causing economic and visual damage

Class B Noxious Weed: Japanese Knotweed

Washington State Noxious Weed Control Board.

Encycloweedia: Data Sheet - Fallopia genus

California Department of Food and Agriculture.

See also: Included on California's noxious weed list; see Encycloweedia: Program Details for additional resources

Field Guide: Invasive - Japanese Knotweed

Missouri Department of Conservation.

Invasive Plants in Pennsylvania: Japanese Knotweed and Giant Knotweed (PDF | 162 KB)

Pennsylvania Department of Conservation and Natural Resources.

See also: Invasive Plant Fact Sheets for plant species (trees, shrubs, vines, herbs and aquatic plants) that have impacted the state's natural lands

Japanese Knotweed (Polygonum cuspidatum)

Wisconsin Department of Natural Resources.

King County (Washington) Noxious Weed Control Program - Japanese Knotweed

King County Department of Natural Resources (Washington). Water and Land Resources Division.

Noxious Weed Species - Japanese, Giant, and Bohemian Knotweeds

Colorado Department of Agriculture. Conservation Services Division. Noxious Weed Program.

Academic

MontGuide - Biology, Ecology and Management of the Knotweed Complex (Aug 2017)

Montana State University Extension.

Biology and Managementof Knotweeds in Oregon:A Guide for Gardeners and Small-Acreage Landowners (Jun 2011)

Oregon State University. Extension Service.

Factsheet: Japanese Knotweed

Pennsylvania State University. Pennsylvania Sea Grant.

See also: Aquatic Invasive Species: Resources for additional species information

Insects, Pests, and Diseases: Japanese Knotweed

Pennsylvania State University. Cooperative Extension.

Introduced Species Summary Project - Japanese Knotweed

Columbia University. Center for Environmental Research and Conservation.

Invasive, Exotic Plants of the Southeast - Japanese Knotweed

North Carolina State University. Cooperative Extension. Going Native: Urban Landscaping for Wildlife with Native Plants.

Maine Invasive Plants Bulletin: Japanese Knotweed / Mexican Bamboo

University of Maine Cooperative Extension.

See also: Maine Invasive Plants & Entire Series for entire series of 22 fact sheets and invasive plants brochure (available in HTML/PDF or for purchase)

Ohio Perennial & Biennial Weed Guide - Japanese Knotweed

Ohio State University. Ohio Agricultural Research and Development Center.

Citations

Integrated Taxonomic Information System. Fallopia japonica. [Accessed Mar 19, 2015].
Stone, K.R. 2010. Polygonum sachalinense, P. cuspidatum, P. × bohemicum. In: Fire Effects Information System. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.