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Polygonum cuspidatum &. Z. Siebold, ucc.
Fallopia japonica var compacta (Hook f) JP Bailey; Fallopia japonica var japonica (Houtt) Ronse Decr; Polygonum compactum Hook f; Fallopia japonica; Reynoutria japonica Houtt; Reynoutria japonica var compacta (Hook f) Moldenke; Fleeceflower; Reynoutria japonica

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Polygonum cuspidatum
© Copyright Bobby Hattaway 2011 · 5
Polygonum cuspidatum
Polygonum cuspidatum
© Copyright Bobby Hattaway 2011 · 5
Polygonum cuspidatum

Polygonum cuspidatum
© Copyright Bobby Hattaway 2011 · 5
Polygonum cuspidatum
Polygonum cuspidatum
© Copyright Bobby Hattaway 2011 · 5
Polygonum cuspidatum

Polygonum cuspidatum
© Copyright Bobby Hattaway 2011 · 4
Polygonum cuspidatum
Polygonum cuspidatum
© Copyright Bobby Hattaway 2011 · 4
Polygonum cuspidatum

Polygonum cuspidatum
© Copyright Bobby Hattaway 2011 · 4
Polygonum cuspidatum
Polygonum cuspidatum
© Les Mehrhoff, 2008-2010 · 4
Polygonum cuspidatum

Polygonum cuspidatum
© Les Mehrhoff, 2008-2010 · 4
Polygonum cuspidatum
Polygonum cuspidatum
© Les Mehrhoff, 2008-2010 · 3
Polygonum cuspidatum

Polygonum cuspidatum
© Les Mehrhoff, 2008-2010 · 2
Polygonum cuspidatum
Polygonum cuspidatum
© Les Mehrhoff, 2008-2010 · 2
Polygonum cuspidatum

Polygonum cuspidatum, flower
© Kay Yatskievych, 2003 · 1
Polygonum cuspidatum, flower
Polygonum cuspidatum
© Les Mehrhoff, 2008-2010 · 1
Polygonum cuspidatum

Polygonum cuspidatum, _leaves_and_stem.JP80279_31.320.jpg
© Photographer/source
Polygonum cuspidatum, leaves and stem
Polygonum cuspidatum.JP80279_01.320.jpg
© Photographer/source
Polygonum cuspidatum

Associates · map
FamilyScientific name @ source (records)
Andrenidae  Andrena hirticincta @ UCMS_ENT (2)

Andrena placata @ UCMS_ENT (2)
Apidae  Bombus citrinus @ UCMS_ENT (1)

Bombus impatiens @ UCMS_ENT (4)

Melissodes druriella @ UCMS_ENT (1)

Nomada electa @ UCMS_ENT (1)

Xylocopa virginica @ UCMS_ENT (4)
Botryosphaeriaceae  Phyllosticta tokutaroi @ BPI (1)
Coccinellidae  Harmonia axyridis @ I_LB (1)
Colletidae  Colletes compactus @ UCMS_ENT (5)

Colletes simulans @ UCMS_ENT (4)
Halictidae  Lasioglossum coriaceum @ UCMS_ENT (1)

Lasioglossum oceanicum @ UCMS_ENT (1)

Lasioglossum versatum @ UCMS_ENT (2)

Sphecodes mandibularis @ UCMS_ENT (1)
Pucciniaceae  Puccinia antenori @ BPI (1)

Puccinia polygoni-amphibii @ BPI (21)
Rhytismataceae  Leptostroma hortense @ BPI (1)
Tricholomataceae  Helotium herbarum @ BPI (1)
_  Microthyriella rubi @ BPI (1)

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Introduced Species Summary Project
Japanese knotweed ( Polygonum cuspidatum
| Project Home | Taxonomy | Identification | Distribution | Introduction Facts | Establishment | Ecology | Benefits | Threats | Control |

Common Name: Japanese knotweed, Mexican bamboo. In Japan, known as itadori.

Scientific Name: Polygonum cuspidatum (most common name in U.S. and Japan), also known as Reynoutria japonica (most common in U.K. and Europe), a movement exists to standardize name as Fallopia japonica.Japanese knotweed

Classification: Plantae

Phylum or Division:  Phylum Magnoliophyta
Class: Magnoliopsida
Order: Polygonales
Family: Polygonacae (knotweeds, buckwheat) "Poly" means many, "gony" from the Greek "knee" means jointed
Subfamily: Polygonum


Identification: Japanese knotweed is an herbaceous perennial that grows very quickly on thick single stems, which appear reddish brown, and includes simple branches when large. Each joint is surrounded by a membranous sheath, making the joint seem swollen. Notable for extreme heighth of branches which arch over and remain, brown, through the winter. Clumps of dark green oval leaves grow 8-10 inches long, 3-6 inches wide, pointed at the tip. Small greenish white flowers appear in the full summer. Seeds are minuscule, reproduces predominately via rhizomes. New growth emerges through the dead brown stems of the previous season, leading to dense thickets.

Original Distribution: Native to Japan, also North China, Taiwan, and Korea.

Current Distribution: Much of mainland Europe, British Isles (except Orkney Islands), at least 36 states in USA including northeastern U.S., California, Pacific Northwest, and Alaska (but not Hawaii, and not usually found south of North Carolina), throughout Canada, Newfoundland, also New Zealand.

Site and Date of Introduction: Intentionally introduced to UK from Japan as an ornamental in 1825 (according to Leslie Seiger, Nature Conservancy, Element Stewardship Abstract), from there made it to U.S. by late nineteenth century. The Dutch botanist Houttuyn named the plant Reynoutria japonica in Japan in 1770, and it was not known until the late 1800s that Polygonum cuspidatum is identical (thus the disparity in scientific names).

Mode(s) of Introduction: Spread by cuttings or pieces of rhizomes, often inadvertently as discards from gardens or carried along rivers or stream beds, where it can colonize extremely quickly after floods.  In Europe, only female plants are found, meaning that each example is a clone, making it one of the biggest females in the world in biomass terms (according to the Japanese Knotweed Alliance).

Reason(s) Why it has Become Established: Grows extremely quickly: within 6 days, a viable plant exists from a rhizome as small as .7 grams, especially when rhizome is in water, which is why river/stream banks tend to get overwhelmed. It grows over 6 feet in first couple months of spring, shading out all other species around it. Even when the visible parts of the plant are cut away, the rhizomes sustain it, making it extraordinarily persistent. Can withstand almost all types of soil, light, and drought conditions. Rhizomes will survive to grow plant even if buried 3 feet deep, or under asphalt.

Ecological Role: In Japan, it is one of the first plants to colonize volcanic areas, it's the "dominant pioneer in the primary succession of volcanic slopes and is frequently a colonizer in secondary succession," (The Nature Conservancy, Element Stewardship Abstract by Leslie Seiger, based on Hirose, 1984). Japanese knotweed has an incredible ability to grow anywhere and thrive under adverse soil conditions. In introduced areas, it helps prevent erosion. Since it reproduces primarily asexually, interactions with other species don't play a large role in the the plant's life outside its native habitat, although it is pollinated by bees and can be eaten by grazing animals. It is found predominately in wetlands, along roadways, and in abandoned areas that have been disturbed (according to the Nature Conservancy Element Stewardship Abstract.

Benefit(s): Can be eaten, good source of vitamin C. Has been used as an ornamental plant along pathways and to create hedges. Due to quick growth and rapid reproduction, useful in erosion control. Also considered a medicinal herb, said to promote group consciousness, sensitivity and telepathy.

Threat(s): Reduces biodiversity because forces out native plants through shade and thick ground cover, damages wildlife habitat by reducing plant biodiversity, expensive to treat, aesthetically displeasing, causes damage to sidewalks and pavement.

Control Level Diagnosis High Priorit y. Extremely difficult and time consuming to eradicate once it is established. Hybridization has already occurred on a wide scale, and the potential exists for much greater interbreeding/evolution, making it even more difficult to control. It has been declared a noxious weed in several states. Because the leaves and stems fall thickly and take a long time to decompose, no other plants (except the new Japanese knotweed shoots) can grow in an affected area. Has the real potential to wreck havoc on native ecosystems.

Control Method : Thoroughly digging out roots and stems takes years to succeed, if it ever does -- if even a tiny speck of stem remains, the plant will regenerate. It is vital to burn or otherwise properly dispose of the plant scraps -- it can ruin a compost pile. It takes a minimum of three years to get rid of it, either by cutting away to the stems and treating each stem with an herbicide such as Roundup or by covering the ground with black plastic and heating the soil to the point where the rhizome dies. The shoots can be eaten by grazing animals, but this doesn't eradicate the plant, only control it. Types of biological control agents (BCA) are being studied; it is known that there are many insects and fungi which control the plant's spread in its native range, so prospects are hopeful (according to the Japanese Knotweed Alliance).

References: The Japanese Knotweed Alliance ( );
The Nature Conservancy, Element Stewardship Abstract for Polygonum cuspidatum by Leslie Seiger ( ); National Park Service Plant Conservation Alliance/Alien Plant Working Group ( ); Wild Man Steve Brill ( ); Delta Gardens (


Author: Alice Brooke Wilson
Last Edited: February 17, 2003.

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Delaware Wildflowers  •  Scientific names

Fallopia japonica (Houtt.) Ronse Decr. ( Polygonum cuspidatum , Reynoutria japonica ) Japanese Knotweed
Polygonaceae — Smartweed family
Invasive non-native
Fallopia japonica
Paper Mill Road
August 2004

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Photos copyright David G. Smith

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You have requested an unaccepted/invalid name entry, the corresponding accepted/valid name is presented here as the result.
Kingdom Plantae  
 Phylum Tracheophyta  
 Class Magnoliopsida  
 Order Caryophyllales  
 Family Polygonaceae  
 Genus Reynoutria  
  Reynoutria japonica    Houtt. 
Provider: sp2k-itis 
hierarchy tree    download xml    download txt    Chinese Page    
Synonyms: Fallopia japonica Pleuropterus cuspidatus Pleuropterus zuccarinii Polygonum cuspidatum Polygonum cuspidatum compactum Polygonum zuccarinii   details
Name Code: ITS-520007
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Polygonum cuspidatum Siebold & Zucc.
Japanese knotweed

Image of Polygonum cuspidatum

General Information
Symbol: POCU6
Group: Dicot
Family: Polygonaceae
Duration: Perennial
Growth Habit : Forb/herb
Native Status : AK   I
L48   I
Data Source and Documentation
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Plants-NRCS Logos
green round image for nativity Native blue round image for introduced Introduced ocre round image for introduced and nativity Both white round image for no status Absent/Unreported
image for native, but no county data Native, No County Data image for introduced, but no county data Introduced, No County Data both introduced and native, but no county data Both, No County Data
Native Status:
lower 48 status L48    Alaska status AK    Hawaii status HI    Puerto Rico status PR    Virgin Islands status VI    Navassa Island NAV    Canada status CAN    Greenland status GL    Saint Pierre and Michelon status SPM    North America NA   


click on a thumbnail to view an image, or see all the Polygonum thumbnails at the Plants Gallery

©Elaine Haug. Provided by Smithsonian Institution, Department of Botany . United States, VA, Woodbridge, Occoquan National Wildlife Refuge. Usage Requirements .

©Elaine Haug. Provided by Smithsonian Institution, Department of Botany . United States, VA, Woodbridge, Occoquan National Wildlife Refuge. Usage Requirements .

Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York. Vol. 1: 676. Provided by Kentucky Native Plant Society . Scanned by Omnitek Inc . Usage Requirements .



Symbol Scientific Name
FAJA2 Fallopia japonica (Houtt.) Ronse Decr.
PLCU3 Pleuropterus cuspidatus (Siebold & Zucc.) Moldenke
PLZU Pleuropterus zuccarinii (Small) Small
POCUC2 Polygonum cuspidatum Siebold & Zucc. var. compactum (Hook. f.) L.H. Bailey
POZU Polygonum zuccarinii Small
REJA2 Reynoutria japonica Houtt.


Click on a scientific name below to expand it in the PLANTS Classification Report.
Rank Scientific Name and Common Name
Kingdom Plantae – Plants
Subkingdom Tracheobionta – Vascular plants
Superdivision Spermatophyta – Seed plants
Division Magnoliophyta – Flowering plants
Class Magnoliopsida – Dicotyledons
Subclass Caryophyllidae
Order Polygonales
Family Polygonaceae – Buckwheat family
Genus Polygonum L. – knotweed
Species Polygonum cuspidatum Siebold & Zucc. – Japanese knotweed

Subordinate Taxa

This plant has no children

Legal Status

Noxious Weed Information
This plant is listed by the U.S. federal government or a state. Common names are from state and federal lists. Click on a place name to get a complete noxious weed list for that location, or click here for a composite list of all Federal and State Noxious Weeds .
Alabama Japanese knotweed, Japanese bamboo Class C noxious weed
California Japanese knotweed B list (noxious weeds)
Connecticut Japanese knotweed Invasive, banned
Massachusetts Japanese knotweed, Japanese arrowroot Prohibited
New Hampshire Japanese knotweed Prohibited invasive Species
Oregon Japanese knotweed "B" designated weed Japanese knotweed Quarantine
Vermont Fallopia japonica Japanese knotweed Class B noxious weed
Washington Japanese knotweed Class B noxious weed Japanese knotweed Noxious weed seed and plant quarantine
U.S. Weed Information
Polygonum cuspidatum Japanese bamboo Japanese knotweed fleeceflower Fallopia japonica Japanese knotweed
This plant and synonym italicized and indented above can be weedy or invasive according to the authoritative sources noted below.This plant may be known by one or more common names in different places, and some are listed above. Click on an acronym to view each weed list, or click here for a composite list of Weeds of the U.S.
STATE Assorted authors. State noxious weed lists for 46 states . State agriculture or natural resource departments.
KY Haragan, P.D.. 1991. Weeds of Kentucky and adjacent states: a field guide . The University Press of Kentucky. Lexington, Kentucky.
N'EAST Uva, R.H., J.C. Neal,and J.M. DiTomaso. 1997. Weeds of the Northeast . Cornell University Press. Ithaca, New York.
SEEPPC Southeast Exotic Pest Plant Council. 1996. Invasive exotic pest plants in Tennessee (19 October 1999). Research Committee of the Tennessee Exotic Pest Plant Council. Tennessee.
WSWS Whitson, T.D. (ed.) et al.. 1996. Weeds of the West . Western Society of Weed Science in cooperation with Cooperative Extension Services, University of Wyoming. Laramie, Wyoming.

Wetland Status

Interpreting Wetland Status


REJA2   Reynoutria japonica Houtt.

North America
Alaska UPL
Arid West FACU
Atlantic and Gulf Coastal Plain UPL
Eastern Mountains and Piedmont FACU
Great Plains FACU
Midwest FACU
Northcentral & Northeast FACU
Western Mountains, Valleys, and Coast FACU

Related Links

More Accounts and Images
ARS Germplasm Resources Information Network (POCU6)
CalPhotos (POCU6)
Flora of North America (POCU6)
Integrated Taxonomic Information System (PLCU3)
Integrated Taxonomic Information System (PLZU)
Integrated Taxonomic Information System (POCU6)
Integrated Taxonomic Information System (POCUC2)
Integrated Taxonomic Information System (POZU)
Integrated Taxonomic Information System (REJA2)
Jepson Interchange (University of California - Berkeley) (POCU6)
Native American Ethnobotany (University of Michigan - Dearborn) (POCU6)
USDA Forest Service Fire Effects Information System (POCU6)
University of Tennessee Herbarium (Distribution) (POCU6)
University of Washington Burke Museum (POCU6)
University of Wisconsin - Stevens Point Freckmann Herbarium (POCU6)
Related Websites
CT-USDA NRCS Invasive Species Identification Sheets (POCU6)
Canada-Invasive Exotic Plant Fact Sheets (POCU6)
Invasive Plant Atlas of New England (POCU6)
MA-Massachusetts Non-Native Plant Introductions (POCU6)
ME-Invasive Plant Fact Sheets (DNR) (POCU6)
NPCI Alien Plant Working Group: abstract & image (POCU6)
The Nature Conservancy: Wildland Weeds Management & Research Program (POCU6)
WA-King County Noxious Weeds (POCU6)
WA-NonNative Freshwater Plants (POCU6)



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