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

Polygonum cuspidatum, _leaves_and_stem.JP80279_31.320.jpg
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Polygonum cuspidatum, leaves and stem
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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)
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)

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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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Polygonum cuspidatum

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Authors: Leslie Seiger, Global Invasive Species Team, The Nature Conservancy


Kingdom: Plantae Phylum: Magnoliophyta Class: Magnoliopsida Order: Polygonales Family: Polygonaceae Genus: Reynoutria Species: R. japonica
Scientific Name
Reynoutria japonica
Sieb. & Zucc.
Scientific Name Synonyms
Fallopia japonica
(Houttuyn) Ronse-Decraene
Polygonum cuspidatum
Siebold & Zucc.
Fallopia japonica var. japonica
(Houtt.) Ronse Decr.
Common Names
Japanese knotweed


Polygonum cuspidatum is an herbaceous perennial that appears woody, reaching 3-10 ft. (1-3 m) tall. Round stems are hollow and covered with scales. Shoots grow from spreading rhizomes that reach 65 ft. (20 m) in length.
Leaves are broadly oblong-ovate or ovate-lanceolate, 3-6 in. (8-15 cm) long and 2-4.75 in. (5-12 cm) wide. Tip of leaves are abruptly acuminate, base of leaves are truncate. Lower leaf surface lacks the minute tri-chomes that similar species possess.
Numerous, greenish-white flowers are in pani-cles in upper axils. Panicles measure 3-6 in. (8-15 cm) long. Flowers are functionally unisexual: male and female flowers still have the complementary organs, but they are vestigial. Inflorescences of male flowers tend to be up-right, while female flowers tend to be drooping. Flowers from Aug. to Sept.
Fruit are papery, winged, and 0.25-0.4 in. (6-10 mm) long. They contain black, smooth, shiny, 3-angled achenes 0.2 in. (3-4 mm) long.
Ecological Threat
Polygonum cuspidatum can be found in a variety of habitats. It thrives in riparian areas and wetlands, but can be found along roadsides and other disturbed areas. It prefers full sunlight, but tolerates moderate shade. Polygonum cuspidatum tolerates high temperatures, dry soil and salt. It is extremely intolerant of frost, and after the first frost, it turns brown and dies back.

General Description

The following is based on descriptions by Fernald (1950), Muenscher (1955), Locandro (1973,1978), and Ohwi (1965).

Polygonum cuspidatum is an herbaceous perennial which forms large clumps 1-3 meters high. It is fully dioecious and can reproduce by seed and by large rhizomes which may reach a length of 5-6 meters. The stout stems are hollow and bamboo-like, extend from an erect base and are simple or little branched and glabrous with thinly membranous sheaths. Leaves are broadly ovate, truncate to cuneate at base, abruptly cuspidate, 5-15 cm long, 5-12 cm broad, with petioles 1-3 cm long. Greenish white flowers 2.5-3 mm long, densely arranged in axillary panicles; 3 styles; 8-10 stamens with longitudinally dehiscing anthers. Fruiting calyx wing-angled, 6-10 mm long. Achenes shiny black-brown, 3-4 mm long, acutely trigonous. Male flowers have branched panicles on upright racemes with the distal end of the raceme in the highest position; individual panicles generally point up. Female flowers are drooping or decumbent with the distal end in the lowest position; individual panicles are not oriented in a particular direction. Both male and female flowers possess vestigial organs of the other sex. Polygonum cuspidatum closely resembles Polygonum sachalinense ( Reynoutria sachalinensis ), an exotic species native to northern Japan and the Sakhalin Islands (Ohwi, 1965). Polygonum sachalinense can be distinguished primarily by its larger size, greenish flowers and cordate leaves which gradually taper to the tip (Fernald, 1950). Polygonum cuspidatum is known to hybridize with Polygonum sachalinense and with Fallopia baldschuanica (Bailey, 1985,1988). Hybrids between Polygonum cuspidatum and Polygonum sachalinense have been frequently mistaken for Polygonum cuspidatum in the U.K. (Bailey, 1990).

Stewardship summary

Polygonum cuspidatum is widely distributed in much of the eastern U.S. In western Pennsylvania it already occupies hundreds of acres of wetlands, streambanks and hillsides and has spread along the banks of the Allegheny and Ohio Rivers and dominates the edges of many of the islands in these rivers (Wiegman, pers.comm.).It is present on at least two sites belonging to the Pennsylvania Chapter of The Nature Conservancy (Long Pond in the Poconos and Bristol Marsh, an urban preserve near Philadelphia)and has become a problem on creeks in suburban Philadelphia (Broaddus, pers. comm.). It is also a serious problem in Rock Creek Park, a national park in Washington D.C. In the U.K., it is considered a major weed and a threat to conservation, and it is legally prohibited to introduce Japanese knotweed into the wild (Beerling, 1990; Nature Conservancy Council, 1989; Palmer, 1990). Its early emergence and great height combine to shade out other vegetation and prohibit regeneration of other species (Sukopp and Sukopp, 1988). Thus it reduces species diversity and damages wildlife habitat (Palmer, 1990; Scott and Mars, 1984; Wiegman, pers. comm.). It does not appear to be a threat in undisturbed forest and other low light areas, but it is likely that, if unchecked, it will continue to expand its range in open habitats. Once Polygonum cuspidatum has established it forms large, almost pure stands which are extremely persistent and difficult to eradicate.

Natural history

Polygonum cuspidatum is native to eastern Asia. It was introduced from Japan to the United Kingdom as an ornamental in 1825, and from there to North America in the late nineteenth century (Conolly, 1977; Patterson, 1976; Pridham and Bing, 1975). In Japan, Polygonum cuspidatum is widely distributed and is usually found in sunny places on hills and high mountains (Kanai, 1983; Ohwi, 1965). It is a dominant pioneeer in the primary succession of volcanic slopes and is frequently a colonizer in secondary succession (Hirose, 1984).

In the U.K., Polygonum cuspidatum has spread extensively, occurring in virtually every 10 km square (Nature Conservancy Council, 1989). Stands range in size from individual plants to clumps more than 500 square meters (Palmer, 1990). Polygonum cuspidatum has also become naturalized in much of central Europe (Sukopp and Sukopp, 1988). In North America, it is widely found in the eastern U.S. and has been observed as far north as Nova Scotia and New Foundland, as far south as North Carolina, in much of the midwest and in the coastal areas of Washington and Oregon (Locandro, 1978; Patterson, 1976; Pauly, 1986). Large stands have been noted in western Pennsylvania, in particular along the banks of the Ohio and Allegheny Rivers and on the islands in these rivers (Wiegman, pers. comm.). Polygonum cuspidatum spreads primarily along river banks, but also grows in wetlands, waste places, along roadways, and in other disturbed areas (Beerling, 1990; Conolly, 1977; Muenscher, 1950).

Polygonum cuspidatum can thrive in a wide variety of habitats. In Japan, it can grow on volcanic soils high in sulfur and having a pH less than 4 (Conolly, 1977). In the U.S., it has been observed growing in a variety of soil types, including silt, loam, and sand, and in soils with pH ranging from 4.5 to 7.4 (Locandro, 1973). Analyses of soils from 17 stands in Wales showed no correlation between stand size and vigor and soil chracteristics. The stands studied grew in soils with a broad range of pH, organic matter and nutrients (Palmer, 1990). In Japan, Polygonum cuspidatum growth is slow, but steady in nutrient poor sites, and rapid in nutrient rich sites (Hirose, 1984). In areas where Polygonum cuspidatum has been introduced, it is found primarily in moist, unshaded habitats. Distribution maps from the U.K. show that it is generally associated with regions of high precipitation (Conolly, 1977). Locandro (1973) reports it growing on xeric as well as hydric sites in the U.S. Its distribution appears to be limited by light. It is found primarily in open sites, and its growth and abundance are depressed in shady sites (Beerling, 1991; Seiger, unpublished data).

Polygonum cuspidatum flowers from July to October in Japan (Ohwi, 1965) and in August and September in the U.K. and North America (Conolly, 1977; Fernald, 1950; Muenscher, 1955). It is pollinated by bees and other insects (Bailey, 1990; Locandro, 1978). Seeds appear about two weeks after flowering (personal observation) and are wind dispersed (Maruta, 1976). In Japan, reproduction in Polygonum cuspidatum is characterized by high seed production and low seedling survival, but plants have a very high probability of survival once established (Hirose and Tateno, 1984). However, in the U.S., U.K, and Europe, seeds do not appear to be a significant mode of reproduction. In a study of the reproductive ecology of Polygonum cuspidatum populations in New Jersey, Locandro (1973) found viable pollen, but noted that fertile males were rare. Seedling germination was observed in the presence of males, but no seedling survival was recorded during five years of observation. In the absence of males, females produced empty achenes. In the U.K., fruit set is very rare. This was originally attributed to the rarity of male fertile flowers (Conolly, 1977). It has since been found that there are no male fertile forms of Polygonum cuspidatum in England and that the pollen source is actually a hybrid between Polygonum cuspidatum and Polygonum sachalinense (Bailey, 1990). Polygonum cuspidatum also hybridizes with Fallopia baldschuanica (Bailey, 1985,1988,1990). In the U.S., hybrids morphologically similar to those between Polygonum cuspidatum and Fallopia baldschuanica have been grown from seeds collected in the field, but seedling establishment has not been observed in the wild (Seiger, unpublished data).

The primary mode of reproduction in the U.S., U.K. and Europe is through extensive rhizomes which can reach 15-20 meters in length (Conolly, 1977; Locandro, 1973). Dispersal can occur naturally when rhizome fragments are washed downstream by the current and deposited on banks or, as more commonly occurs, when soil is transported by humans as fill dirt (Conolly, 1977; Locandro, 1978). Rhizomes can regenerate from small fragments, and have even been observed to regenerate from internode tissue (Locandro, 1973). Rhizomes can regenerate when buried up to 1 meter deep and have been observed growing through two inches of asphalt (Locandro, 1978; Pridham and Bing, 1975). The ability of rhizomes to generate shoots was found to be affected by the source of rhizome fragments, fragment size and depth planted, the optimal depth being just below the surface (Locandro, 1973).

Polygonum cuspidatum requires high light environments and effectively competes for light in such environments by emerging early in the spring and using its extensive rhizomatous reserves to quickly attain a height of 2-3 meters. Shoots generally begin to emerge in April and growth rates exceeding 8 cm per day have been recorded (Locandro, 1973). In addition, its deep root system gives it an advantage in foraging for nutrients and water, and contributes to soil stabilization on disturbed sites (Hirose and Tateno, 1984; Nakamura, 1984). Hirose and Tateno (1984) found that organic nitrogen levels on Mt. Fuji increased following colonization by Polygonum cuspidatum on bare volcanic desert and concluded that Polygonum cuspidatum contributes to the development of the ecosystem, in part, by acting as a nutrient reservoir.

Polygonum cuspidatum is found on open sites and does not appear to be able to invade forest understory due to its high light requirements (Beerling, 1991). Studies of the very closely related Polygonum sachalinense indicated that Polygonum sachalinense plants grown in low light did not have higher photosynthetic rates than plants grown in high light, and thus would not be expected to adapt to sites with low light intensity (Patterson, Longstreth and Peet, 1977). Transplant studies of Polygonum cuspidatum in closed understory sites showed poor survival and growth compared to open bank sites, confirming that it was environmental factors and not limitations on dispersal which exclude Polygonum cuspidatum from understory sites (Seiger and Merchant, 1991). Follow-up studies in the greenhouse showed that Polygonum cuspidatum grown under light levels comparable to those found in the understory had significantly less rhizomatous reserves at the end of the season than did plants grown under full sunlight (Seiger, unpublished data).

Polygonum cuspidatum occurs in much of the temperate U.S. Though not yet a major weed in the U.S., it is spreading, particularly in the eastern states. Dispersal is limited to areas where rhizome fragments from existing stands are washed downstream or soil containing rhizomes is transported by humans. Once established, it forms large, monospecific stands which displace virtually all other vegetation. Establishment can be prevented by monitoring for the introduction of Polygonum cuspidatum and manually removing the entire plant. Small stands may be controlled by repeated cutting, which may need to be supplemented by revegetation once growth of Polygonum cuspidatum has been reduced. At present, the only method to control large stands is with repeated application of herbicides. Complete eradication may not be possible.


Current control methods (mechanical, herbicidal) require continued treatment to prevent reestablishment of Polygonum cuspidatum . It may be feasible to reintroduce competitors as an alternative to continued treatment. There is a need for more research on whether native species might serve effectively as competitors and methods of reintroduction. Only very preliminary work has been done towards developing a biological control for Polygonum cuspidatum and much research remains to be done (see below).

The International Institute for Biological Control in conjunction with the National Agricultural Research center in Japan has produced a partial list of insect herbivores in Japan which are associated with Polygonum cuspidatum . A number of pathogens have been collected from Japan by CAB International and are held at the International Mycological Institute (Fowler and Schroeder, 1990). Plans are under way to begin a study of Polygonum cuspidatum in its native habitat (Fowler, pers. comm.). Contact:

Dr. Simon V. Fowler
International Institute of Biological Control
Silwood Park
Buckhurst Road
Ascot, Berks, SL5 7TA, UK

Recent studies in Rock Creek park, Washington, D.C. indicate potential for control by mechanical means combined with revegetation (Seiger, unpubished data). Field tests will be conducted in 1992. Contact:

Leslie Seiger PhD
Biology Department
California State University, San Diego
9500 Gilman Dr.,
La Jolla, CA 92093-0346
Phone Number: 619-594-6328

In areas where Polygonum cuspidatum has not yet become established, the focus of management should be to prevent establishment by monitoring areas for introductions of Polygonum cuspidatum and eradicating newly established stands before they can become established.

Manual control consists of digging out the rhizomes or cutting the stalks. Digging is extremely labor intensive and tends to spread the rhizome fragments and promote disturbance and is not recommended (Palmer, 1990). Cutting, on the other hand, may be quite effective in eliminating Polygonum cuspidatum . It has been observed that Polygonum cuspidatum does not establish where grazing pressure is high (Beerling, 1990; Palmer, 1990). In a review of control methods, Palmer (1990) noted that eradication is not complete with cutting alone, but has been nearly achieved in some cases and should be feasible with persistence. A number of authors claim that cutting is ineffective (Pauly, 1986; Pridham and Bing, 1975; Orchowski, 1991). These conclusions are based on the observation that shoots are regenerated following cutting. However, a greenhouse study found that cutting stems results in a significant reduction of rhizomatous reserves. The same study also found that cutting was equally effective at any time during the growing season prior to the beginng of senescence (Seiger and Merchant, 1990). A study of the effects of repeated cutting showed that at least three cuts are needed in a growing season to offset rhizome production (Seiger, unpublished data). Manual control can be labour intensive, but where populations are small and isolated, may be the best option. No research has been done to test the effectiveness of burning. It may act similarly to cutting by removing above ground material.

Shading, particularly in conjunction with cutting, may be another useful means of control on smaller stands. Studies showing that P. cuspidatum requires high light environments suggest that covering stands with black plastic or shade cloth may reduce growth. Pridham and Bing (1975) state that applying several layers of black polyethylene film covered by asphalt, blocks or stones to a leveled soil surface may provide some control. However, they also note that P. cuspidatum is able to emerge through asphalt. If shade cloth (or plastic) is to be applied without cutting, then, to prevent P. cuspidatum from emerging through the covering, shade cloth should be placed over shoots after the plants have reached their full height or placed well above newly emerging shoots, or raised as plants grow.

A number of biocidal chemicals have been found to be effective against Polygonum cuspidatum . Most of these are undesirable for use in conservation areas because they are nonselective, may be persistent in the soil and/or are not safe for use near water. One frequently used way to minimize the effects of non-selective herbicides on non-target species is to paint herbicides directly onto the target plants (Broaddus, pers. comm.). In the case of P. cuspidatum , this would probably require prior cutting for easier access if herbicides are to be applied after the plants have reached their full height. Herbicides appear to be more effective when combined with cutting (Scott and Mars, 1984; Orchowski, 1991).

Glyphosate [N-(phophonomethyl)glycine] has been found to be very effective against Polygonum cuspidatum (Ahrens, 1975; Beerling, 1990; Pauly, 1986). Glyphosate is a nonselective systemic herbicide with a short residual life (Ahrens, 1975; Lynn, Rogers and Graham,1979). Application is more effective in the fall when leaves are translocating to rhizomes (Lynn, et al, 1979). The British Nature Conservancy Council (1989) recommends applying 2.0 kg/ha in August with a prior cut in late spring or early summer. Glyphosate is available from Monsanto under the trade names Roundup ® and Rodeo ® . Only Rodeo has been approved for use near water (Bender, 1988). Glyphosate has been used with limited success on some nature reserves in the U.K. (Palmer, 1990). Repeated applications over several years may be necessary (Beerling, 1990; Palmer, 1990; Pauly, 1986).

The Nature Conservancy Council (1989) also recommends picloram to be applied at a rate of 2.6 kg/ha in the spring. Picloram is a selective herbicide which is persistent in the soil. It must not be used near water, thus excluding its use in many of the areas where Polygonum cuspidatum is a problem (Gritten, 1990; Scott and Mars, 1984). Dicamba (3,6-dichloro-o-anisic acid) has also been found to be effective against Polygonum cuspidatum , but is persistent in the soil and nonselective (Pridham and Bing, 1975). A number of other herbicides have been tested against Polygonum cuspidatum , both alone and in combination with other herbicides (Orchowski, 1991; Scott and Mars, 1984). Herbicide may have to be used on stands that have been allowed to attain a large size. However, their use is not recommended in nature reserves because of their undesirable effects on other biota and the need for repeated applications to maintain control of Polygonum cuspidatum .

Regardless of whether control is manual or chemical, as long as some rhizomes remain in the soil Polygonum cuspidatum returns once management is relaxed (Beerling, 1990; Nature Conservancy Council, 1989; Palmer, 1990). It has been suggested that the reintroduction of effective competition might be possible (Eaton, 1986). Research has only recently begun on biological control. The herbivores and pathogens of Polygonum cuspidatum in Wales have been examined for their potential as control agents (Fowler and Schroeder,1990). A program is underway at the International Institute of Biological Control to identify biological control agents (Fowler, pers. comm.). The genetic uniformity of Polygonum cuspidatum makes it a good candidate for biological control (Bailey, 1990). Biological control may be necessary where Polygonum cuspidatum has taken over vast areas as it has done in the U.K., but it may be years before a successful control agent can be found. The following individuals are familiar with Polygonum cuspidatum and its control in natural areas:

Leslie Seiger PhD
Biology Department
California State University, San Diego
9500 Gilman Dr.,
La Jolla, CA 92093-0346
Phone Number: 619-594-6328

John Palmer
Richards Moorehead & Laing Ltd
3 Clwyd Street
Clwyd LL15 1HF, Wales

Jonathan Soll
The Nature Conservancy of Oregon
821 SE 14th Ave
Portland OR 97214
503-230-1221 x329 or


It is extremely difficult, if not impossible to eradicate large established stands of Polygonum cuspidatum . However, establishment can be prevented fairly easily by removing Polygonum cuspidatum before it becomes firmly entrenched. Areas known to be near established stands of Polygonum cuspidatum , particularly those downstream from such stands, should be monitored for the introduction of Polygonum cuspidatum . The following individuals have direct experience monitoriing Polygonum cuspidatum :

Leslie Seiger PhD
Biology Department
California State University, San Diego
9500 Gilman Dr.,
La Jolla, CA 92093-0346
Phone Number: 619-594-6328

Robert Orchowski, Director, Air Quality, Environmental Affairs Unit
Duquesne Light
One Oxford Center
301 Grant Street
Pittsburgh, PA 15279

John Palmer
Richards Moorehead & Laing Ltd
3 Clwyd Street
Clwyd LL15 1HF, Wales
David Beerling
School of Pure & Applied Biology
University of Wales
PO Box 915
Cardiff CF1 3TL, Wales

Information sources

Species resources

Static files


Ahrens, J.F. (1975). Preliminary results with glyphosate for control of Polygonum cuspidatum . Proc. Northeast. Weed Science Soc. 29:326.

Bailey, J.P. (1985). Chromosome numbers of some alien Reynoutria species in the British Isles. Watsonia, 15:269-277.

Bailey, J.P. (1988). Putative Reynoutria japonica Houtt. x Fallopia baldschuanica (Regel) Holub hybrids discovered in Britain. Watsonia, 17:163-181.

Bailey, J.P. (1990). Breeding behaviour and seed production in Alien Giant Knotweed in the British Isles. In: The biology and control of invasive plants. Conference organized by the Industrial Ecology Group of the British Ecological Society at the University of Wales College of Cardiff, September 20-21, 1990.

Beerling, D.J. (1990). The use of non-persistent herbicides to control riparian stands of Japanese Knotweed ( Reynoutria Japonica Houtt). In: The biology and control of invasive plants. Conference organized by the Industrial Ecology Group of the British Ecological Society at the University of Wales College of Cardiff, September 20-21, 1990.

Beerling, D.J. (1991). The effect of riparian land use on occurrence and abundance of Japanese knotweed Reynoutria japonica on selected rivers in South Wales. Biol. Cons. 55:329-337.

Bender, J. (1988). Element Stewardship Abstract for Lythrum salicaria . The Nature Conservancy.

Broaddus,L. (1992). The Nature Conservancy, Pennsylvania Chapter. Memorandum to Leslie Seiger, March 6, 1992.

Conolly, A.P. (1977). The distribution and history in the British Isles of some alien species of Polygonum and Reynoutria . Watsonia 11:291-311.

Eaton, J.W. (1986). Waterplant ecology in landscape design. In Ecology and design in landscape. The 24th symposium of the British Ecological Society, Manchester 1983. A.D. Bradshaw, D.A. Goode, E.H.P. Thorp (Eds.). Blackwell Scientific Publications. Oxford.

Fernald, M.L. (1950). Gray's Manual of Botany. 8th Ed. American Book Company, N.Y.

Fowler, S.V. (1991). International Institute of Biological Control. Silwood Park, Buckhurst Road, Ascot, Berks, SL5 7TA, UK. Letter to Leslie Seiger, January 8, 1991.

Fowler, S.V. and D. Schroeder (1990). Biological control of invasive plants in the UK - prospects and possibilities. In: The biology and control of invasive plants. Conference organized by the Industrial Ecology Group of the British Ecological Society at the University of Wales College of Cardiff, September 20-21, 1990.

Gritten, R. (1990). The control of invasive plants in the Snowdonia National Park. In: The biology and control of invasive plants. Conference organized by the Industrial Ecology Group of the British Ecological Society at the University of Wales College of Cardiff, September 20-21, 1990.

Hirose, T. (1984). Nitrogen use efficiency in growth of Polygonum cuspidatum Sieb. et Zucc. Annals of Botany, 54:695-704.

Hirose, T., and M. Tateno (1984). Soil nitrogen patterns induced by colonization of Polygonum cuspidatum on Mt. Fuji. Oecologia 61:218-223.

Kanai, H. (1983). Study on the distribution patterns of Japanese plants (5): Accumulation of phytogeographical data of popular plants, points and measures. Journ. Jap. Bot., 59: 257-269.

Locandro, R.R. (1973). Reproduction ecology of Polygonum cuspidatum . Ph.D. thesis. Rutgers University.

Locandro, R.R. (1978). Weed watch: Japanese bamboo - 1978. Weeds Today 9:21-22.

Lynn, L.B., R.A. Rogers, and J.C. Graham (1979). Response of woody species to glyphosate in northeastern United States. Proc. Northeast Weed Sci. Soc. 33:336-342.

Maruta, E. (1976). Seedling establishment of Polygonum cuspidatum on Mt. Fuji. Jap. J. Ecol. 26:101-105.

Maruta, E. (1983). Growth and survival of current-year seedlings of Polygonum cuspidatum at the upper distributional limit on Mt. Fuji. Oecologia 60:316-320.

Muenscher, W.C. (1955). Weeds. Second edition. McMillan Press, New York.

Nakamura, T. (1984). Vegetational recovery of landslide scars in the upper reaches of the Oi River, Central Japan. J, Jap. For. Soc. 66(8):328-332.

Nature Conservancy Council (1989). Japanese knotweed. In Urban Wildlife News, 6(2):3.

Ohwi, J. (1965). Flora of Japan. Smithsonian Institute, Washington, DC.

Orchowski, R.W. (1991). Knotweed control pilot program Brunot Island Wildlife Habitat Enhancement Project. Presented at the 3rd Annial Wildlife Enhancement Council Symposium, Washington, DC, November 19, 1991.

Palmer, J.P. (1990). Japanese knotweed ( Reynoutria japonica ) in Wales. In: The biology and control of invasive plants. Conference organized by the Industrial Ecology Group of the British Ecological Society at the University of Wales College of Cardiff, September 20-21, 1990.

Patterson, D.T. (1976). The history and distribution of five exotic weeds in North Carolina. Castanea 41:177-180.

Patterson, D.T., D.J. Longstreth, and M.M. Peet (1977). Photosynthetic adaptation to light intensity in Sakhalin knotweed ( Polygonum sachalinense ). Weed Science 25:319-323.

Pridham, A.M.S. and A. Bing (1975). Japanese-bamboo plants. Gard. 31:56-57.

Pauly,W.R. (1986). Summary of Mexican bamboo control methods (Wisconsin). Restoration and Management Notes, 4(1):37-38.

Scott, R., and R.H. Mars (1984). Impact of Japanese knotweed and methods of control. Aspects of applied biology 5, Weed control and vegetation managemnet in forestry and amenity areas pp. 291-296.

Seiger, L.A. and H.C. Merchant (1990). The ecology and control of Polygonum cuspidatum . Bull. Ecol. Soc. Am. 71(2 suppl.):322.

Seiger, L.A. and H.C. Merchant (1991). Effects of site on survivorship and size of Polygonum cuspidatum . Bull. Ecol. Soc. Am. 72(2 suppl.):247.

Sukopp, H. and U. Sukopp (1988). Reynoutria japonica Houtt. in Japan und in Europa. Veroff. Geobot. Inst. ETH, Stiftung Rubel, Zurich 98:354-372.

Wiegman, P. (1992). Director of natural science and stewardship, Western Pennsylvania Conservancy, Pittsburgh, PA. Telephone conversation with Leslie Seiger, February 25, 1992.

Original Document

Element Stewardship Abstract; L. Seiger, 1991

Articles in Archived Publications

Retrieved from " "

Following modified from Flora of Taiwan, National Taiwan University
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&pull 20q v4.662 20091102: Error 301 Moved Permanently

Following modified from Delaware Wildflowers
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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

More information on this plant, from other sources.

Copyright David G. Smith

Delaware Wildflowers main page

Following modified from
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Polygonum cuspidatum Sieb. & Zucc.

Polygonum cuspidatum plant

Family - Polygonaceae

Stems - No info. yet.

Polygonum cuspidatum stem Node of stem.

Leaves - No info. yet.

Polygonum cuspidatum leaves Upper leaves.

Polygonum cuspidatum leaf Lower leaf.

Inflorescence - No info. yet.

Polygonum cuspidatum inflorescence

Flowers - No info. yet.

Polygonum cuspidatum flowers

Flowering - August - September.

Habitat - Waste ground, fence rows, roadsides, railroads.

Origin - Native to Japan.

Other info. - This large, showy species can be found scattered throughout Missouri but is still mostly uncommon. It will most certainly spread with time. The plant is quite large and bushy, growing to +4m tall. It makes a good cultivated specimen but is hard to keep under control. When left undisturbed it spreads rapidly. The sprays of white flowers attract many insects.
P. cuspidatum is considered a noxious weeds in many parts of the U.S.

Photographs taken in Marquette, MI., 9-8-03.


Following modified from Taiwan Biodiversity National Information Network
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Kingdom Plantae  
 Phylum Magnoliophyta  
 Class Magnoliopsida  
 Order Polygonales  
 Family Polygonaceae  
 Genus Polygonum  
  Polygonum cuspidatum    Sieb. & Zucc., 1846 
Provider: Ching-I Peng 
hierarchy tree    download xml    download txt    Chinese Page    
Synonyms: Fallopia japonica Pleuropterus cuspidatus Pleuropterus zuccarinii Polygonum cuspidatum compactum Polygonum zuccarinii Reynoutria japonica   details
Citation: Flora of Taiwan 2nd ed. 2: 299, 1996
Name Code: 203883
Suggested Link    Discover Life    National Plant Genetic Resources Center    Flora of Taiwan 2nd eBooks (National Taiwan University)  
User Response:   upload Comments    upload Photo
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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
About our new maps
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)



Source Large Mammals Small Mammals Water Birds Terrestrial Birds


Source Large Mammals Small Mammals Water Birds Terrestrial Birds

Description of Values

Value Class Food Cover

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Following modified from CalPhotos
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CalPhotos     Photo Database


Number of matches : 9
Query: SELECT * FROM img WHERE ready=1 and taxon like "Polygonum cuspidatum%" and (lifeform != "specimen_tag" OR lifeform != "Plant") ORDER BY taxon

Click on the thumbnail to see an enlargement

Polygonum cuspidatum
Polygonum cuspidatum
Japanese Knotweed
ID: 0000 0000 0105 0471 [detail]
© 2005 Louis-M. Landry

Polygonum cuspidatum
Polygonum cuspidatum
Japanese Knotweed
ID: 0000 0000 0105 2337 [detail]
© 2005 Louis-M. Landry

Polygonum cuspidatum
Polygonum cuspidatum
Japanese Knotweed
ID: 0000 0000 0105 2338 [detail]
© 2005 Louis-M. Landry

Polygonum cuspidatum
Polygonum cuspidatum
Japanese Knotweed
ID: 0000 0000 0105 2341 [detail]
© 2005 Louis-M. Landry

Polygonum cuspidatum
Polygonum cuspidatum
Japanese Knotweed
ID: 0000 0000 0105 2342 [detail]
© 2005 Louis-M. Landry

Polygonum cuspidatum
Polygonum cuspidatum
ID: 0000 0000 0509 1790 [detail]
© 2009 Barry Rice

Polygonum cuspidatum
Polygonum cuspidatum
ID: 0000 0000 0509 1791 [detail]
© 2009 Barry Rice

Polygonum cuspidatum
Polygonum cuspidatum
ID: 0000 0000 0509 1792 [detail]
© 2009 Barry Rice

Polygonum cuspidatum
Polygonum cuspidatum
ID: 0000 0000 0509 1804 [detail]
© 2009 Barry Rice

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