Japanese Knotweed | National Invasive Species Information Center

Scientific Name

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

Common Name

Japanese knotweed, fleeceflower, Mexican bamboo, huzhang

Synonym

Polygonum cuspidatum Siebold & Zucc.; Reynoutria japonica Houtt.

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)

Japanese knotweed, foliage

Credit

Photo by Jack Ranney; University of Tennessee

Source

Invasive.org.

Find more images

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.

Videos

YouTube - How to: ID and Manage Invasive Knotweeds
- Google. YouTube; Invasive Species Council of British Columbia (Canada).

All Resources

View and Filter All Japanese Knotweed Resources

Selected Resources

The section below contains highly relevant resources for this species, organized by source.

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 [PDF, 304 KB]
- Feb 7, 2011
- 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
- CAB International.
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

Biology and Biological Control of Knotweeds [PDF, 13.34 MB]
- Apr 2020
- USDA. FS. Forest Health Technology Enterprise Team.
- FHTET-2017-03. See also: FHAAST Publications for more resources.
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) [PDF, 237 KB]
- 2014
- 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 [PDF, 373 KB]
- 2012
- 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 [PDF, 734 KB]
- 2006
- 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 ID - 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.
Maine Invasive Plants Bulletin: Japanese Knotweed / Mexican Bamboo
- University of Maine Cooperative Extension.
- See also: Natural Resources Publications for entire "Maine Invasive Plants" series
Ohio Perennial & Biennial Weed Guide - Japanese Knotweed
- Ohio State University. Ohio Agricultural Research and Development Center.

Professional

Knotweeds (Fallopia spp.) - History and Ecology in North America [PDF, 7.62 MB]
- 2022
- North American Invasive Species Management Association.
- See also: Biocontrol Factsheets for more information on biocontrol agents

Citations

Integrated Taxonomic Information System. Fallopia japonica. [Accessed Sep 16, 2023].
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.