Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Fallopia sachalinensis
(giant knotweed)

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Datasheet

Fallopia sachalinensis (giant knotweed)

Summary

  • Last modified
  • 19 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Preferred Scientific Name
  • Fallopia sachalinensis
  • Preferred Common Name
  • giant knotweed
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Dicotyledonae
  • Summary of Invasiveness
  • F. sachalinensis is a highly invasive rhizomatous perennial plant capable of reaching 4 m in height, outcompeting and displacing native species in particular in riparian zones which it prefers. It has spread to m...

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Pictures

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PictureTitleCaptionCopyright
Fallopia sachalinensis (giant knotweed); stand in Wales, UK.  Note scale of person in picture - Dr Dick Shaw is 1.85m (73") tall.
TitleHabit
CaptionFallopia sachalinensis (giant knotweed); stand in Wales, UK. Note scale of person in picture - Dr Dick Shaw is 1.85m (73") tall.
Copyright©CABI/Harry C. Evans
Fallopia sachalinensis (giant knotweed); stand in Wales, UK.  Note scale of person in picture - Dr Dick Shaw is 1.85m (73") tall.
HabitFallopia sachalinensis (giant knotweed); stand in Wales, UK. Note scale of person in picture - Dr Dick Shaw is 1.85m (73") tall.©CABI/Harry C. Evans
Fallopia sachalinensis (giant knotweed); stand in Wales, UK. Note scale of person in picture - Dr Dick Shaw is 1.85m (73") tall.
TitleHabit
CaptionFallopia sachalinensis (giant knotweed); stand in Wales, UK. Note scale of person in picture - Dr Dick Shaw is 1.85m (73") tall.
Copyright©CABI/Harry C. Evans
Fallopia sachalinensis (giant knotweed); stand in Wales, UK. Note scale of person in picture - Dr Dick Shaw is 1.85m (73") tall.
HabitFallopia sachalinensis (giant knotweed); stand in Wales, UK. Note scale of person in picture - Dr Dick Shaw is 1.85m (73") tall.©CABI/Harry C. Evans
Fallopia sachalinensis (giant knotweed); leaf with hand for scale.
TitleFoliage
CaptionFallopia sachalinensis (giant knotweed); leaf with hand for scale.
Copyright©CABI/Richard H. Shaw
Fallopia sachalinensis (giant knotweed); leaf with hand for scale.
FoliageFallopia sachalinensis (giant knotweed); leaf with hand for scale.©CABI/Richard H. Shaw
Fallopia sachalinensis (giant knotweed); leaf with hand for scale.
TitleFoliage
CaptionFallopia sachalinensis (giant knotweed); leaf with hand for scale.
Copyright©CABI/Richard H. Shaw
Fallopia sachalinensis (giant knotweed); leaf with hand for scale.
FoliageFallopia sachalinensis (giant knotweed); leaf with hand for scale.©CABI/Richard H. Shaw
Fallopia sachalinensis (giant knotweed); flower. Note various Dipterans on florets.
TitleFlower
CaptionFallopia sachalinensis (giant knotweed); flower. Note various Dipterans on florets.
Copyright©CABI/Richard H. Shaw
Fallopia sachalinensis (giant knotweed); flower. Note various Dipterans on florets.
FlowerFallopia sachalinensis (giant knotweed); flower. Note various Dipterans on florets.©CABI/Richard H. Shaw

Identity

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Preferred Scientific Name

  • Fallopia sachalinensis (F. Schmidt) Ronse Decr.

Preferred Common Name

  • giant knotweed

Other Scientific Names

  • Pleuropterus sachalinensis (F.W. Schmidt ex Maxim.) H. Gross
  • Polygonum sachalinense F. Schmidt
  • Reynoutria sachalinensis (F. Schmidt) Nakai
  • Reynoutria vivax J. Schmitz and Strank
  • Tiniaria sachalinensis (F.W. Schmidt ex Maxim.) Janch.

Local Common Names

  • Poland: rdest sachalinski; rdestowiec sachalinski

Summary of Invasiveness

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F. sachalinensis is a highly invasive rhizomatous perennial plant capable of reaching 4 m in height, outcompeting and displacing native species in particular in riparian zones which it prefers. It has spread to most areas in its exotic range without the aid of seed dispersal though it does provide pollen for the fertilization of F. japonica plants to produce the highly invasive Fallopia x bohemica. Though not considered as problematic as Japanese knotweed (F. japonica), eradication is a real challenge and often unachievable, especially with restrictions applied to chemical use on or near water thus methods of control are limited.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Dicotyledonae
  •                     Order: Polygonales
  •                         Family: Polygonaceae
  •                             Genus: Fallopia
  •                                 Species: Fallopia sachalinensis

Notes on Taxonomy and Nomenclature

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Fallopia sachalinensis has been placed in a number of different genera including Polygonum, Reynoutria, Tiniaria and Pleuropterus, before being accepted as a member of Fallopia, However, it must be noted when searching for information that it is still found in the literature as Reynoutria sachalinensis and transfer back to Reynoutria was proposed by Galasso et al. (2009) based on rbcL plastidial sequence analysisIt is commonly known as giant knotweed, not to be confused with the closely related Japanese knotweed, F. japonica, although all species in the genus Fallopia are collectively known as ‘knotweeds’. F. sachalinensis also hybridizes with F. japonica, forming self-sustaining and even more highly invasive populations of F. xbohemica.

 

Description

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The following description is taken from the electronic Flora of North America (http://www.efloras.org/flora). Herbs, perennial, rhizomatous, 2-4(-5) m. Stems usually clustered, erect, sparingly branched, herbaceous, stiff, glabrous, glaucous. Leaves: ocrea persistent or deciduous, brownish, cylindric, 6-12 mm, margins oblique, face without reflexed and slender bristles at base, otherwise glabrous or puberulent; petiole 1-4 cm, glabrous; blade ovate-oblong, 15-30(-40) × 7-25 cm, base cordate, margins entire, glabrous or scabrous to ciliate, apex obtuse to acute, abaxial face minutely dotted, glaucous, with hairs along veins distinctly multicellular, 0.2-0.6 mm, tips acute to acuminate, adaxial face glabrous. Inflorescences axillary, mostly distal, erect or spreading, panicle like, 3-8 cm, axes puberulent to pubescent; peduncle 0.1-4 cm or absent, puberulent to reddish-pubescent. Pedicels ascending or spreading, articulated proximal to middle, 2-4 mm, glabrous. Flowers bisexual or pistillate, 4-7 per ocreate fascicle; perianth accrescent in fruit, greenish, 4.5-6.5 mm including stipe-like base, glabrous; tepals obovate to elliptic, apex obtuse to acute, outer 3 winged; stamens 6-8; filaments flattened proximally, glabrous; styles connate basally; stigmas fimbriate. Achenes included, brown, 2.8-4.5 × 1.1-1.8 mm, shiny, smooth; fruiting perianth glabrous, wings flat to undulate, 1.8-2.2 mm wide at maturity, decurrent on stipelike base to articulation, margins entire.

Plant Type

Top of page Broadleaved
Herbaceous
Perennial
Vegetatively propagated

Distribution

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F. sachalinensis is a native of Japan (northern Honshu and Hokkaido only), Sakhalin Island (Russia) and possibly the isolated Ullung-do Island between Korea and Japan (Bailey and Conolly, 2000). Sukopp and Starfinger (1995) reports it in the southern Kuril Islands of Kunashir and Shikotan. In Japan it is found from sea-level to 1050 m (Miyawaki, 1989)

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

IndiaPresentPresent based on regional distribution.
-West BengalLocalisedIntroducedBailey and Conolly, 2000To stabalise riverbanks
JapanPresentPresent based on regional distribution.
-HokkaidoWidespreadNative Not invasive Kanai, 2000
-HonshuLocalisedNative Not invasive Kanai, 2000

Africa

South AfricaPresentIntroducedRussell et al., 1987

North America

CanadaPresentPresent based on regional distribution.
-British ColumbiaPresentIntroducedUSDA-NRCS, 2008
-New BrunswickPresentIntroducedUSDA-NRCS, 2008
-Newfoundland and LabradorPresentIntroducedUSDA-NRCS, 2008
-Nova ScotiaPresentIntroducedUSDA-NRCS, 2008
-NunavutPresenteFloras, 2008
-OntarioPresentIntroducedUSDA-NRCS, 2008
-Prince Edward IslandPresentIntroducedUSDA-NRCS, 2008
-QuebecPresentIntroducedUSDA-NRCS, 2008
USAPresentPresent based on regional distribution.
-AlaskaPresentIntroducedUSDA-NRCS, 2008
-CaliforniaLocalisedIntroduced Invasive USDA-NRCS, 2008
-ConnecticutLocalisedIntroducedUSDA-NRCS, 2008
-DelawarePresentIntroducedUSDA-NRCS, 2008
-IdahoLocalisedIntroducedUSDA-NRCS, 2008
-IllinoisLocalisedIntroduced Invasive USDA-NRCS, 2008Invasiveness confirmed by Swearingen (2006)
-LouisianaLocalisedIntroduced Invasive USDA-NRCS, 2008
-MaineLocalisedIntroduced Invasive USDA-NRCS, 2008Invasiveness confirmed by Swearingen (2006)
-MarylandLocalisedIntroduced Invasive USDA-NRCS, 2008Invasiveness confirmed by Swearingen (2006)
-MassachusettsLocalisedIntroduced Invasive USDA-NRCS, 2008
-MichiganLocalisedIntroduced Invasive USDA-NRCS, 2008Invasiveness confirmed by Swearingen (2006)
-MinnesotaLocalisedIntroduced Invasive USDA-NRCS, 2008Invasiveness confirmed by Swearingen (2006)
-MontanaLocalisedIntroduced Invasive USDA-NRCS, 2008
-New JerseyLocalisedIntroduced Invasive USDA-NRCS, 2008
-New YorkLocalisedIntroduced Invasive USDA-NRCS, 2008
-North CarolinaLocalisedIntroduced Invasive USDA-NRCS, 2008Invasiveness confirmed by Swearingen (2006)
-OhioLocalisedIntroduced Invasive USDA-NRCS, 2008
-OregonWidespreadIntroduced Invasive USDA-NRCS, 2008Invasiveness confirmed by Swearingen (2006)
-PennsylvaniaLocalisedIntroduced Invasive USDA-NRCS, 2008
-Rhode IslandLocalisedIntroduced Invasive USDA-NRCS, 2008Invasiveness confirmed by Swearingen (2006)
-TennesseeLocalisedIntroduced Invasive USDA-NRCS, 2008
-VermontPresentIntroducedUSDA-NRCS, 2008
-VirginiaLocalisedIntroduced Invasive USDA-NRCS, 2008
-WashingtonLocalisedIntroduced Invasive USDA-NRCS, 2008Invasiveness confirmed by Swearingen (2006)
-West VirginiaPresentIntroducedUSDA-NRCS, 2008
-WisconsinLocalisedIntroduced Invasive USDA-NRCS, 2008Invasiveness confirmed by Swearingen (2006)

Europe

AustriaLocalisedIntroducedSukopp and Starfinger, 1995; EPPO, 2014Ref refers to most central and eastern Europe
BelgiumWidespreadIntroduced Invasive Tiébré et al., 2007; EPPO, 2014
BulgariaLocalisedIntroducedSukopp and Starfinger, 1995; EPPO, 2014Ref refers to most central and eastern Europe
CroatiaLocalisedIntroducedSukopp and Starfinger, 1995; EPPO, 2014Ref refers to most central and eastern Europe
CyprusPresentEPPO, 2014
Czech RepublicWidespreadIntroduced1921 Invasive Mandák et al., 2004; EPPO, 2014
DenmarkWidespreadIntroduced1950 Invasive Royal Botanic Garden Edinburgh, 2008; EPPO, 2014
EstoniaWidespreadIntroduced Invasive Royal Botanic Garden Edinburgh, 2008; EPPO, 2014
FinlandPresentIntroduced Invasive Royal Botanic Garden Edinburgh, 2008; EPPO, 2014
FranceWidespreadIntroduced Invasive Marigo and Pautou, 1998; EPPO, 2014
-CorsicaAbsent, no pest recordEPPO, 2014
GermanyWidespreadIntroduced1917 Invasive Schnitzler and Muller, 1998; EPPO, 2014
GreecePresentIntroduced Invasive DAISIE, 2008
HungaryLocalisedIntroducedSukopp and Starfinger, 1995Ref refers to most central and eastern Europe
IrelandWidespreadIntroduced Invasive Royal Botanic Garden Edinburgh, 2008; EPPO, 2014
ItalyLocalisedIntroduced Invasive DAISIE, 2008
LithuaniaLocalisedIntroducedSukopp and Starfinger, 1995Ref refers to most central and eastern Europe
LuxembourgLocalisedIntroduced Invasive DAISIE, 2008
NetherlandsLocalisedIntroduced Invasive DAISIE, 2008; EPPO, 2014
NorwayPresent Invasive Fremstad and Elven, 1997; EPPO, 2014
PolandWidespreadIntroduced Invasive Royal Botanic Garden Edinburgh, 2008; EPPO, 2014
RomaniaLocalisedIntroducedSukopp and Starfinger, 1995Ref refers to most central and eastern Europe
Russian FederationRestricted distributionEPPO, 2014
-Central RussiaPresentIntroducedRoyal Botanic Garden Edinburgh, 2008; EPPO, 2014
-Northern RussiaPresent only in captivity/cultivationIntroducedRegel, 1864; Sukopp and Starfinger, 1995
-Russian Far EastPresentMorozov, 1978; USDA-ARS, 2008; EPPO, 2014
-Southern RussiaPresentIntroducedRoyal Botanic Garden Edinburgh, 2008
SerbiaLocalisedIntroducedSukopp and Starfinger, 1995
SlovakiaLocalisedIntroducedSukopp and Starfinger, 1995Ref refers to most central and eastern Europe
SloveniaLocalisedIntroducedSukopp and Starfinger, 1995; EPPO, 2014Ref refers to most central and eastern Europe
SpainPresent only in captivity/cultivationIntroduced Invasive DAISIE, 2008; EPPO, 2014
SwedenLocalisedIntroduced Invasive Royal Botanic Garden Edinburgh, 2008; EPPO, 2014
SwitzerlandLocalisedIntroduced Invasive Jeanmonod, 2005; EPPO, 2014
UKLocalisedIntroduced1800s Invasive Pashley et al., 2007; EPPO, 2014
UkrainePresentEPPO, 2014

Oceania

AustraliaPresentPresent based on regional distribution.
-New South WalesLocalisedIntroduced Invasive Royal Botanic Garden Edinburgh, 2008
-VictoriaLocalisedIntroducedRoyal Botanic Garden Edinburgh, 2008
New ZealandPresentIntroduced1935 Invasive

History of Introduction and Spread

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The plant was first discovered by Dr H Weyrich in Sakhalin during a Russian naval expedition from 1852-55, bringing it to St Petersburg in 1864 and it was reported as growing in the city’s botanical gardens in the same year (Regel, 1864). It was introduced to the UK in the late 1860s, first appearing for sale in the 1869-70 catalogue (no. 48) of the horticulturalist William Bull of Chelsea. In The Garden (vol xiii, 1878), it was referred to as even more vigorous than Polygonum cuspidatum (= F. japonica) and well adapted to the wild garden, and if well placed on the edge of a shrubbery it will well repay the planter. It was recommended as a forage plant for cattle in Europe (Andre, 1893) and was even established in Bengal as a riverbank stabilizer where it still persists (Bailey and Conolly, 2000). It was introduced to New Zealand in 1935 (Owen, 1996) and also to Victoria and New South Wales, Australia. It is also recorded in South Africa from as early as 1987 (Russell Gibbs et al., 1987). Dates of first introduction to North America are not reported though it is now found in most states of the USA and provinces of Canada.

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Europe Japan 1863 Food (pathway cause) ,
Ornamental purposes (pathway cause)
Yes Sukopp and Starfinger (1995)
Russian Federation Japan 1859 Botanical gardens and zoos (pathway cause)Bailey and Conolly (2000)
UK Japan 1859 Botanical gardens and zoos (pathway cause) Yes Bailey and Conolly (2000)

Risk of Introduction

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F. sachalinensis is fairly well known by, and unpopular with, the gardening public so the risk of new introductions in areas where ‘knotweeds’ have become problematic are unlikely. It is possible that an unwitting public may purchase the plant from unscrupulous sellers but the chance of this is fairly small. It could arrive in new areas as a result of the import of contaminated soil. It is a regulated species in four states of the USA, and the closely related Japanese knotweed is a declared weed much more widely in Europe and North America.

Habitat

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In its adventive range it is found either in sites more or less influenced by human activities such as gardens, parks and ruderal sites in towns and villages, often close to planted individuals, or along watercourses in near-natural conditions.

Habitat List

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CategoryHabitatPresenceStatus
Littoral
Coastal dunes Secondary/tolerated habitat Harmful (pest or invasive)
Terrestrial-managed
Disturbed areas Principal habitat Harmful (pest or invasive)
Rail / roadsides Principal habitat Harmful (pest or invasive)
Urban / peri-urban areas Principal habitat Harmful (pest or invasive)
Terrestrial-natural/semi-natural
Natural forests Secondary/tolerated habitat Productive/non-natural
Natural grasslands Secondary/tolerated habitat Harmful (pest or invasive)
Riverbanks Principal habitat Harmful (pest or invasive)
Wetlands Secondary/tolerated habitat Harmful (pest or invasive)

Hosts/Species Affected

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Any riparian species would be vulnerable to displacement by giant knotweed and those natives that are threatened and not widely distributed would be more vulnerable to localized extinction. The most common species associated with the plant relevés in Germany were Urtica dioca, Artemisia vulgaris, Poa palustris, P. trivialis and Aegopodium podagraria (Dettmar, 1991).

Biology and Ecology

Top of page Genetics

In Korea, F. sachalinensis occurs as dodecaploids (2n=132) which is the highest count so far found (JeongYeon and Chong Wook, 2000), though several lower ploidy levels have been recorded (2n=44, 66, 102 and 132 in Japan and Korea. It has proven to be more genetically diverse in Europe than F. japonica (Hollingsworth et al., 1998), probably due to multiple introductions. F. sachalinensis also hybridizes with the closely related F. japonica, forming self-sustaining and even more highly invasive populations of F. xbohemica.

Reproductive Biology

In its native range of Japan the plant reproduces sexually with hermaphrodite and male-sterile stands (Tanaka, 1966) as well as by vegetative regeneration (Maruta, 1981). As both hermaphrodite and female individuals are present in the UK, pure bred seeds are formed and the plant can also reproduce sexually and asexually. The plants have been shown to be self-incompatible (Bailey, 1989). However, we know of no location where the two sexes grow together, and there are few places where male F. sachalinensis grows with F. japonica var. japonica. Sexual reproduction between giant and Japanese knotweed has been observed through the resulting seedlings in the field in the USA (Forman and Kesseli, 2003; Zika and Jacobson, 2003), and it seems clear that introgression is occurring in North America (Gammon et al., 2007; Grimsby et al., 2007). 

Physiology and Phenology

It is reported as being capable of growth rates of 4-5 cm per day (Marigo and Pautou, 1998). Furthermore the plant has very high leaf area index of 21 (Numata and Yoshizawa, 1975), which is higher than those found in the densest forest. Also biomass production was found to be 259.2 t ha-1 (Numata and Yoshizawa, 1975). Leaves and foliage contain 82% moisture; the plant grows 7-14 ft (about 2-4 m) high during a summer and can withstand frosts reaching -40°C (Steiger, 1957). 

Associations

F. sachalinensis is not known to form mycorrhizal relationships (Frydman, 1957), but is often found in its native range associated with ants which are attracted by its extra-floral nectaries (Kawano et al., 1999), which is also the case in parts of Europe (Sukopp and Schick, 1991). 

Environmental Requirements

Like Japanese knotweed, giant knotweed seems to be very tolerant of a wide range of soils from volcanic ash to muddy riverbanks. The nutritional value of such extreme soil types will be highly variable. In general, the plant thrives in light (sandy), medium (loamy) and heavy (clay) soils and acid, neutral and basic (alkaline) soils. It can grow in semi-shade (light woodland) or no shade but requires moist soil. In ruderal habitats the plant prefers dry and warm conditions but in mountainous riparian zones it prefers wet and cool conditions (Sukopp and Starfinger, 1995). It seems to be intolerant of drought as many leaves were lost at a site in Germany during a hot summer (Dettmar, 1991). In its native range it is found in regions with a mean annual temperature of 4-8°C and with mean annual rainfall varying from 500 mm to over 1,000 mm. It dominates in volcanic ash soil with a pH of 4-5 (Yuasa et al., 1995).

Climate

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ClimateStatusDescriptionRemark
Cf - Warm temperate climate, wet all year Tolerated Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year
Cs - Warm temperate climate with dry summer Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Cw - Warm temperate climate with dry winter Tolerated Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)
Df - Continental climate, wet all year Tolerated Continental climate, wet all year (Warm average temp. > 10°C, coldest month < 0°C, wet all year)
Ds - Continental climate with dry summer Preferred Continental climate with dry summer (Warm average temp. > 10°C, coldest month < 0°C, dry summers)
Dw - Continental climate with dry winter Tolerated Continental climate with dry winter (Warm average temp. > 10°C, coldest month < 0°C, dry winters)

Air Temperature

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Parameter Lower limit Upper limit
Absolute minimum temperature (ºC) -40 0
Mean annual temperature (ºC) 4 8
Mean maximum temperature of hottest month (ºC) 16 26
Mean minimum temperature of coldest month (ºC) -9 -3

Rainfall

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ParameterLower limitUpper limitDescription
Dry season duration00number of consecutive months with <40 mm rainfall
Mean annual rainfall5001200mm; lower/upper limits

Rainfall Regime

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Soil Tolerances

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Soil drainage

  • free
  • impeded
  • seasonally waterlogged

Soil reaction

  • acid
  • alkaline
  • neutral

Soil texture

  • heavy
  • light
  • medium

Special soil tolerances

  • infertile
  • saline

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Aphalara itadori Herbivore Leaves/Stems to genus
Gallerucida bifasciata Herbivore Leaves to genus
Mycosphaerella Pathogen Leaves to species
Puccinia polygoni-amphibii var. torariae Pathogen Leaves to genus

Notes on Natural Enemies

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The congeneric F. japonica has been subject to research into biological control since 1999, and in that time dozens of natural enemies have been recorded on F. sachalinensis in its native range, in contrast with very few that have been found in its introduced range.

Means of Movement and Dispersal

Top of page Natural Dispersal (Non-biotic)

Like Japanese knotweed, F. sachalinensis can regenerate from stem fragments (Hrušková and Hofbauer, 1999), and as such can spread very easily along rivers after flood events or from dumped garden waste. 

Vector Transmission (Biotic)

There are no known biotic vectors. 

Accidental Introduction

Rhizome fragments can be carried on machinery that has not been adequately cleaned. Such material can also arrive as a contaminant of imported topsoil in landscaping and building activities. The use of snow ploughs can also inadvertently spread the plant to new areas along transport corridors. 

Intentional Introduction

Giant knotweed has a long history as a garden ornamental which was highly prized thanks to its impressive size and enormous leaves. Although it is no longer popular, it is feasible that less scrupulous or ill advised horticulturalists may still sell the plant in some countries.

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Botanical gardens and zoosMost introductions began in botanical gardens Yes Bailey, 1989
Escape from confinement or garden escapevery common indeed Yes Bailey and Conolly, 2000
Flooding and other natural disasters Yes Sukopp and Starfinger, 1995
Garden waste disposalflytipping common issue in UK Yes
Habitat restoration and improvementEven exported to India Yes Bailey and Conolly, 2000
HorticultureOriginally but not anymore Yes
Intentional releaseIt is planted as a crop in Germany for the production of Milsana Yes
Interconnected waterwaysDuring flood events Yes

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Land vehiclesEarch moving equipment Yes
Machinery and equipmentEarth moving equipment Yes Yes
Soil, sand and gravelContamination by rhizome Yes
WaterFlood events Yes

Impact Summary

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CategoryImpact
Cultural/amenity Negative
Economic/livelihood Negative
Environment (generally) Negative
Human health None

Economic Impact

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F. sachalinensis, like Japanese knotweed is difficult and expensive to control, and the economic impacts are felt mainly through the costs of control efforts. It is also considered alongside Japanese knotweed when assessing potential building land in the UK and its presence can add up to 10% on the total project cost. Although not found to cause disease within cattle, cattle fed on the plant exhibited transient anorexia and hypothermia (Suzuki et al., 1985).

Environmental Impact

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F. sachalinensis is suspected to alter critical riparian processes including forest and understory regeneration, streambank stability, soil nutrient cycling and allochthonous litter inputs. 

Impact on Habitats

Like F. japonica, F. sachalinensis is quite capable of excluding native plants and their associated herbivores after invasion and the creation of mono-specific stands. On riverbanks, the high production of slowly-decomposing leaf litter means that nutrient cycling is likely to be compromised with the associated knock-on effects on the site ecology. The presence of giant knotweed on riverbanks also exacerbates flooding in much the same way as Japanese knotweed (Child and Wade, 2000). The inclusion of living as well as dead stems in a river can lead to blockage and reduced water flow.

The plant also demonstrates allelopathy since giant knotweed root exudates have been shown to significantly inhibit lettuce seedling growth (Inoue et al., 1992), and that anthraquinones in the rhizomes and fallen leaves are responsible for the observed allelopathy.

The following is taken from Urgenson and Reichard (2007). An analysis of nutrient reabsorption from senescing leaves revealed that knotweed reabsorbed 75.5% of its foliar nitrogen prior to litterfall. In contrast, native species reabsorbed only 5-33%, thus contributing a greater proportion of their nitrogen resources to riparian soils and aquatic environments through leaf litter. Reductions in juvenile coniferous and broadleaf trees associated with knotweed invasion may limit development of overstory trees and alter succession in riparian forests. Loss of riparian trees can have long lasting and detrimental effects on bank stability, hydrology, nutrient loading, habitat quality and productivity of adjacent lotic systems. Additionally, leaf litter from riparian vegetation comprises a primary source of nutrients and energy in forested streams and backwater channels. By displacing native vegetation and altering the species composition and nutrient quality of litter inputs, knotweed invasion can affect the structure and productivity of riparian forests and adjacent aquatic habitats.          

Impact on Biodiversity

Biodiversity impacts have been shown to be negative in the case of ground-dwelling coleopteran (Topp et al., 2008) and are presumed to be the same as those encountered with Japanese knotweed as demonstrated for frogs reduced foraging success (Maerz et al., 2005). Floral and faunal diversity is generally reduced after invasion of riparian habitats (Gerber et al., 2008).

Social Impact

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Like Japanese knotweed, F. sachalinensis is often associated with neglected and disturbed urban environments and as such can have a social impact and be a symbol of decay and a lack of investment.

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Abundant in its native range
  • Highly adaptable to different environments
  • Is a habitat generalist
  • Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
  • Pioneering in disturbed areas
  • Long lived
  • Fast growing
  • Has propagules that can remain viable for more than one year
  • Reproduces asexually
Impact outcomes
  • Conflict
  • Damaged ecosystem services
  • Ecosystem change/ habitat alteration
  • Increases vulnerability to invasions
  • Infrastructure damage
  • Loss of medicinal resources
  • Modification of fire regime
  • Modification of hydrology
  • Modification of natural benthic communities
  • Monoculture formation
  • Negatively impacts tourism
  • Reduced amenity values
  • Reduced native biodiversity
  • Threat to/ loss of native species
Impact mechanisms
  • Allelopathic
  • Interaction with other invasive species
  • Rapid growth
  • Rooting
Likelihood of entry/control
  • Difficult to identify/detect as a commodity contaminant
  • Difficult/costly to control

Uses

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Giant knotweed contains compounds that are beneficial for pest management purposes and one product Milsana™ has been found to be effective against microbial diseases of some crops (Metcalfe and Wale, 1997; Trottin-Caudalet al., 2003). 

Economic Value

Giant knotweed contains compounds that are beneficial for pest management purposes and one product Milsana™ has been found to be effective against microbial diseases of some crops (Metcalfe and Wale, 1997; Trottin-Caudalet al., 2003).

It has been considered as a biofuel since it is capable of producing up to 68.2-69.5 t DM/ha, with an above ground:below ground ratio of 1:3 and an annual growth rate of 31.8-32.8 t/ha (Stepanova and Rassokhina, 1981). 

Social Benefit

The young shoots are edible, and taste somewhat like rhubarb (Pojar and MacKinnon, 1994). 

Environmental Services

Giant knotweed has been shown to accumulate heavy metals from the soils in which it grows (Wilke and Metz, 1992). In the former USSR it was promoted as a living firebreak since leaves and foliage contain 82% moisture; the plant grows 2-4 m high during a summer and can withstand frosts reaching -40°C. Tests in Sakhalin, Russia of its fire-resistant properties indicated that thickets are a completely effective barrier against low forest fires and can be recommended for planting in firebreaks (Steiger, 1957). It is also reported as having a useful amount of tanning agents (Jakimov, 1941) though this is likely to have been superseded by more modern techniques.

Detection and Inspection

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Identification of newly propagated plants is possible, but rhizomes are hard to distinguish from other invasive knotweeds.

Similarities to Other Species/Conditions

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Giant knotweed is very closely-related to Japanese knotweed, F. japonica although it can be distinguished fairly easily as it is generally a much larger plant, 4-5 m tall with much larger leaves 20-40 cm long, with trichomes present on the underside, and also distinguished by the base of the leaf which in F. sachalinensis is rounded acuminate forming a heart shape. More difficult to distinguish is their hybrid F. xbohemica which has an intermediate leaf size and shape between the two parents. A useful key to the identification of invasive knotweeds has been developed for British Columbia, Canada and includes drawings and photographs (Wilson, 2007).

Prevention and Control

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Prevention

F. sachalinensis is listed as declared in the following states of the USA (USDA-ARS, 2008; USDA-NRCS, 2008): California, noxious weed b-list; Connecticut, potentially invasive and banned; Oregon, “B” designated weed and Quarantine; and Washington, class “B” noxious weed. The related Japanese knotweed is included in the UK Wildlife and Countryside Act (1981), meaning that its intentional spread in the country is limited. Screening of imported soil for rhizome contamination should prevent movement within a country.  

Early warning systems
 
F. sachalinensis is recorded on the Nobanis network and DAISIE databases so new arrivals in countries currently unaffected should be picked up. However, it is likely to be confused with Fallopia x bohemica by inexperienced recorders.

Rapid response

If a recently established patch is identified, then treatments with systemic herbicides after the plant has reached full height are most likely to kill the plant. However, digging out as much rhizome as possible is advantageous prior to a spraying regime. 


Public awareness

Giant knotweed is normally lumped together with Japanese knotweed in awareness raising and information campaigns. See for example: http://www.idahoweedawareness.org/vfg/weedlist/giantknotweed/giantknotweed.html (specifically giant knotweed).

General knotweed awareness-raising websites:




http://www.lanecounty.org/Roads/Vegetation/documents/JapaneseKnotweedflyer.pdf

Eradication

Giant knotweed is presumed to be as difficult to eradicate as Japanese knotweed since it also benefits from a very large rhizome system with an ability to regenerate from very small fragments of rhizome. In the UK, the Environment Agency has produced a Code of Practice for knotweed management which provides information on control measures and management on development sites. Eradication can be achieved by the removal of the whole plant and the contaminated soil to landfill sites but this is far from sustainable. Various companies have been set up in the UK that guarantee total knotweed eradication, though the value of these guarantees is yet to be tested. Some companies avoid landfill by using mechanical sieves to remove the majority of rhizome from the extracted soil and then follow-up spot spraying for any small plants that do re-establish. 

Containment/zoning

The use of physical barriers is common in building sites in the UK, where thick rubberized sheeting is used to create a sealed parcel of contaminated soil underground. 

Control 

Physical/mechanical control

A comparative study of control measures used on the various knotweeds (Bïmová et al., 2001) showed that digging led to a greater biomass reduction of F. sachalinensis than F. x bohemica, whereas cutting had the opposite effect. Mowing has been considered and a study in the Czech Republic using traditional meadow management with mowing and grazing suggested that such traditional management, provided it is applied continuously, may represent an effective barrier against invasion (Brabec and Pyšek, 2000). 

Movement control

Japanese knotweed infested soil is dealt with as a contaminated waste issue in the UK, and as such its transport and burial are regulated by the Environment Agency. 

Biological control

A biological control programme has been underway since 2003 against the closely related Japanese knotweed, which has involved research on behalf of the UK, USA and Canada. In this time, surveys have been undertaken in Northern Honshu and Hokkaido where giant knotweed is the dominant or only knotweed in the area. Numerous natural enemies of giant knotweed have been identified including a northern strain of the sap-sucking psyllid Aphalara itadori, the chrysomelid beetle Gallerucida bifasciata and the pyralid moth Ostrinia ovalipennis amongst many other arthropods and fungi. Giant knotweed has not been the priority target so far but it is included in the host range testing procedures undertaken by the partner institutions so potential biological control agents may emerge in this on-going collaborative research project 

Chemical control

It is rare to find specific information about the control of giant knotweed as separated from the more common Japanese knotweed for which there has been much written. In general the key to successful control with chemicals is to use a systemic chemical once the plant has reached its full height but before the first winter frost. In this way, the largest leaf to rhizome ration is presented and proportionally more chemical is absorbed through the leaves and moved along with the carbohydrates to kill the root. Herbicides containing glyphosate can be effective and have an advantage over the more persistent herbicides containing imazypyr, picloram and dicamba in that they have a lower soil activity. Care must be taken when using chemicals in general and especially on or near water where restrictions exist. 

Host resistance

With limited sexual reproduction in the introduced range there is no evidence of variable resistance to chemical treatments. 

IPM programmes

Combined treatments were also found to be more successful on F. sachalinensis than on two other taxa (Bímová et al., 2001). F. japonica was best controlled by the combined treatment consisting of digging and subsequent herbicide application. F. sachalinensis was well controlled by both the combined treatments and by purely mechanical disturbance of underground biomass. Combination treatments can provide more cost-effective control than purely chemical or mechanical measures (Child et al., 1998) and normally involves disturbance followed by systemic chemical treatment. 

Control by utilization

Whereas giant knotweed can be eaten, used as a source of medicinal or anti-microbial products or as a biofuel, these resources are recovered from crop situations rather than invasive infestations. 

Monitoring and Surveillance

GIS mapping and public questionnaires have been used to establish the extent of Japanese knotweed in the UK and USA and are often included in management plans. 

Ecosystem Restoration

Following giant knotweed control there may be a need to re-establish native plant species if the control measures have left bare and disturbed ground.

Gaps in Knowledge/Research Needs

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More information on the genetic diversity and distribution of giant knotweed in North America would be useful. In addition, a biocontrol programme against this species appears justified.

References

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Links to Websites

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WebsiteURLComment
GISD/IASPMR: Invasive Alien Species Pathway Management Resource and DAISIE European Invasive Alien Species Gatewayhttps://doi.org/10.5061/dryad.m93f6Data source for updated system data added to species habitat list.

Contributors

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20/05/08 Original text by:

Dick Shaw, CABI Europe  - UK, Bakeham Lane, Egham, Surrey TW20 9TY, UK

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