Fallopia x bohemica
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Plant Type
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Hosts/Species Affected
- Biology and Ecology
- Notes on Natural Enemies
- Pathway Causes
- Pathway Vectors
- Impact Summary
- Economic Impact
- Environmental Impact
- Threatened Species
- Social Impact
- Risk and Impact Factors
- Uses List
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Gaps in Knowledge/Research Needs
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Fallopia x bohemica (J. Chrtek & A. Chrtková) J. P. Bailey
Other Scientific Names
- Polygonum x bohemicum (J. Chrtek & A. Chrtková) P.F. Zika & A.L. Jacobson
- Reynoutria x bohemica J. Chrtek & A. Chrtková
International Common Names
- English: bohemian knotweed; hybrid knotweed
Local Common Names
- Poland: rdest posredni; rdestowiec posredni
- Sweden: hybridslide
Summary of InvasivenessTop of page
It is generally an under-recorded component of the knotweed populations. It occupies the same sorts of habitat as Japanese knotweed (F. japonica) does in its adventive range. There is some evidence that it is more difficult to control than its parents (Bimova et al., 2003) and that it can exploit a wider range of habitat than its parents (Bailey and Wisskirchen, 2006). Some clones cover very large areas.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Dicotyledonae
- Order: Polygonales
- Family: Polygonaceae
- Genus: Fallopia
- Species: Fallopia x bohemica
Notes on Taxonomy and NomenclatureTop of page
Fallopia x bohemica (Chrtek & Chrtková) J.P. Bailey (Stace, 1989) is the hybrid between Fallopia japonica and Fallopia sachalinensis and occurs at three different ploidy levels: 2n=44; 66; and 88. Although most literature nowadays refers to it under the Fallopia combination, older papers refer to Reynoutria x bohemica Chrtek & Chrtková, and the Americans have even published the Polygonum combination; Polygonum x bohemicum (Zika and Jacobson, 2003). There are two reasons behind this generic plentitude. Firstly, Japanese knotweed [Fallopia japonica] was described twice independently, the first name Reynoutria japonica being lost for more than 100 years, and in the mean time it was described again as Polygonum cuspidatum (Bailey and Stace, 1992). However, many taxonomists now accord generic status to the former sections of the Linnaean genus Polygonum. Fallopia and Reynoutria were then the correct names for the genera containing the climbers and the Japanese knotweeds, respectively. In the 1980s, morphological and hybridization studies indicated that these two genera should be merged under Fallopia, the older name (Ronse Decraene and Akeroyd, 1988; Bailey and Stace, 1992). A recent molecular study by Galsasso et al. (2009) proposes the transfer back to Reynoutria and The Plant List (2013) gives Reynoutria x bohemica Chrtek & Chrková as the preferred name.
DescriptionTop of page
It has the same general growth form as F. japonica var. japonica, but the leaves are much larger and do not have the truncate bases so typical of F. japonica. Unlike F. japonica var. japonica, both sexes are found, and in the UK at least, the hermaphrodites seem to outnumber the male-sterile plants. Clones extend by rhizome growth and may occupy considerable areas.
Inflorescences are similar to those of either of the parents. Florets are 1-2.5 mm long and functionally unisexual but with each male or female flower possessing the complementary but vestigial, organs of the other sex. Each floret has 5 petals and 8 stamens (Gillespie and Faithfull, 2004).
Plant TypeTop of page Herbaceous
DistributionTop of page
Bailey et al. (1996) give detailed information about the distribution in the British Isles with six figure grid references; more up to date data on a 10 km square basis is to be found in Preston et al. (2002).
Distribution TableTop of page
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/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Japan||Present||Bailey, 2003||Recently discovered|
|Canada||Present||Present based on regional distribution.|
|-British Columbia||Present||Invasive||USDA-NRCS, 2008|
|USA||Present||Present based on regional distribution.|
|-Connecticut||Present||Invasive||Gammon et al., 2007|
|-Maine||Present||Invasive||Gammon et al., 2007|
|-Massachusetts||Present||Invasive||Gammon et al., 2007|
|-New Hampshire||Present||eFloras, 2008|
|-New York||Present||Invasive||eFloras, 2008|
|-North Carolina||Present||eFloras, 2008|
|-Rhode Island||Present||Invasive||Gammon et al., 2007|
|-Vermont||Present||Invasive||Gammon et al., 2007|
|-West Virginia||Present||eFloras, 2008|
|Belgium||Widespread||Invasive||Meerts and Tiebre, 2007|
|Czech Republic||Present||Invasive||Mandák et al., 2004; Mandák et al., 2004; EPPO, 2014||Very extensive and spreading|
|Denmark||Present||Invasive||Jonsell and Karlsson, 2000; Bailey and Wisskirchen, 2006|
|Finland||Present||Jonsell and Karlsson, 2000; EPPO, 2014||Vaasa since late 1960's. Helsinki since 1987|
|France||Present||Invasive||Bailey and Wisskirchen, 2006; Schnitzler et al., 2007; Schnitzler and Bailey, 2008||Some very extensive colonies present|
|Germany||Present||Invasive||Keil and Alberternst, 1995; Bailey and Wisskirchen, 2006; EPPO, 2014||Extensive colonies present throughout the country, high densities in the Ruhr|
|Hungary||Present||Invasive||Balogh, 1998; Balogh, 2003; Botta-Dukát and Balogh, 2008; EPPO, 2014||F. bohemica is more common than F. japonica|
|Ireland||Present||Invasive||Bailey et al., 1996; Preston et al., 2002; EPPO, 2014||Some long established colonies in the West and in Dublin|
|Italy||Present||Invasive||Bailey and Wisskirchen, 2006; Padula et al., 2008||Mainly restricted to Northern Italy|
|Netherlands||Present||Adolphi, 1999; Bailey and Wisskirchen, 2006; EPPO, 2014|
|Norway||Widespread||Fremsted and Elven, 1997; Jonsell and Karlsson, 2000; Bailey and Wisskirchen, 2006; EPPO, 2014||Present in 12 municipalities, some consisting of more than 10 records|
|Poland||Widespread||Invasive||Fojcik and Tokarska-Guzik, 2000; Bailey and Wisskirchen, 2006; EPPO, 2014|
|Romania||Present||Botta-Dukát and Balogh, 2008; EPPO, 2014||Mentioned in text, no further details|
|Russian Federation||Present||EPPO, 2014|
|-Central Russia||Present||EPPO, 2014|
|Slovakia||Widespread||Fehér, 1999; Eliás, 2001||Widespread - some large colonies present|
|Sweden||Present||Jonsell and Karlsson, 2000||5 localities reported - first record Uppsala 1975|
|Switzerland||Present||Botta-Dukát and Balogh, 2008; EPPO, 2014||Ticino and other places - more or less the same frequency as F. japonica (C Krebs, pers. comm.)|
|UK||Widespread||Bailey et al., 1996; Preston et al., 2002; EPPO, 2014||Widespread with some very large colonies|
|-Channel Islands||Present||Invasive||Bailey et al., 1996; Preston et al., 2002|
|-England and Wales||Present||EPPO, 2014|
|Ukraine||Present||Botta-Dukát and Balogh, 2008||Presence reported but no further details provided|
|Australia||Present||Present based on regional distribution.|
|-New South Wales||Present||Not invasive||Conolly, 1998; Conolly, 2001||Sydney|
History of Introduction and SpreadTop of page
Initially this species was thought to be part of the range of variation of Fallopia japonica var. japonica, and it was only with the application of cytology that it became apparent that there was no morphological variation in the UK F. japonica var. japonica (subsequently shown to be a male-sterile clone) and that the morphologically intermediate plants were actually the hybrid. It was only discovered in the 1980s, therefore its earlier history can only be established by a study of dated herbarium specimens (Bailey and Conolly, 2000). The fact that all F. japonica var. japonica were male-sterile, meant that once male-fertile plants of Fallopia sachalinensis reached Europe, hybridization was inevitable. Any seed collected from Japanese knotweed would thus be of hybrid origin. Botanic gardens around the world were distributing this hybrid seed as F. japonica. Evidence from herbarium material shows that this hybrid arose not long after the arrival of F. sachalinensis in the late nineteenth century (Bailey and Conolly, 2000), whereas the earliest date for a plant established in the wild is currently 1954 for County Durham, UK.
Risk of IntroductionTop of page
The main method of reproduction is by vegetative propagation so there is a danger of river-borne fragments of rhizome crossing country borders. Also there are some reports of short, sea-borne transfer of viable rhizome fragments of Fallopia japonica from island to island in the west of Scotland (Beerling et al., 1994; Hayward, 2002) and there is nothing to suggest that F. x bohemica is any less adept in this ability so this possibility cannot be excluded. Richards et al. (2008) describe the presence of F. japonica and F. x bohemica in salt marsh habitats in the USA and performed experiments that indicated that both taxa exhibited considerable plasticity in their response to exposure to salt. There is little risk of inadvertent transport to continents not already occupied.
HabitatTop of page
It occurs in habitats similar to those occupied by Fallopia japonica; principally in riparian and ruderal habitats, but also in salt marshes (Richards et al., 2008).
Habitat ListTop of page
|Rivers / streams||Principal habitat||Harmful (pest or invasive)|
|Salt marshes||Present, no further details|
|Disturbed areas||Principal habitat|
|Managed forests, plantations and orchards||Present, no further details|
|Rail / roadsides||Principal habitat|
|Urban / peri-urban areas||Principal habitat|
|Riverbanks||Principal habitat||Harmful (pest or invasive)|
Hosts/Species AffectedTop of page
Not usually a problem in cultivated ground.
Biology and EcologyTop of page
ClimateTop of page
|C - Temperate/Mesothermal climate||Preferred||Average temp. of coldest month > 0°C and < 18°C, mean warmest month > 10°C|
Notes on Natural EnemiesTop of page
No specific research has been carried out on F. x bohemica because it is rarely found in Japan, but much of what holds for Fallopia japonica might be expected to apply to the hybrid. F. japonica in Japan is attacked by a suite of natural enemies, both arthropod and fungal, not present in its adventive range. To date, 186 species of arthropod and around 40 species of fungus have been recorded from the plant in its native range of Japan (R Shaw, CABI, UK, personal communication, 2008). As a result of this attack, it is not able to compete with local flora as effectively as it does in the introduced range and does not normally reach the same massive size. Of these natural enemies, some exert significant damage such as the chrysomelid beetle Gallerucida nigromaculata, which is described as having potential as a biocontrol agent by Zwoelfer (1973). This is now thought to be Gallerucida bifasciata and not adequately specific. Recent observations by CABI Bioscience show fungal pathogens, as well as arthropods, are significant controlling factors in Japan, across the climatic range of the plant. This includes a number of obligate biotrophic fungi, as well as an ubiquitous leafspot pathogen. In its introduced range, F. japonica is attacked by the green dock beetle, Gastrophysa viridula, but this is only when its normal Rumex host has been consumed and beetle populations are elevated.
Pathway CausesTop of page
Pathway VectorsTop of page
Impact SummaryTop of page
|Cultural/amenity||Positive and negative|
Economic ImpactTop of page
The economic impact of this species is similar to that of Fallopia japonica in that it is a problem for developers of land infested with F. x bohemica, although it is not entirely clear whether this taxon is actually covered by the letter of the law that proscribes Japanese knotweed (1981 Wildlife and Countryside Act). It is unsightly in amenity areas and a threat to biodiversity along water courses, where, like F. japonica, it is able to spread vegetatively. Control costs will equal, if not exceed, the costs for F. japonica, as there is some evidence (Bimova et al. 2003) that the hybrid is more difficult to eradicate than either parent.
For F. japonica the estimated annual control costs for one county council in Wales, UK, in 1994 was £300,000 (approximately US $600,000). The budget needed to control the 64 ha knotweed infestation in the city and county of Swansea was estimated to be £5.79 million in 1998 (Shaw et al., 2001). To control F. japonica on a national scale in the UK would cost an extrapolated £1.56 billion (approximately US $3 billion) were it to be attempted, as reported by the UK Department of Environment, Food and Rural Affairs in its recent non-native species policy review. An accepted estimate of control costs is £10,000 per hectare for a 3-year spraying regime, with two sprays per year, but this is probably an underestimate if revegetation costs are taken into account. Its presence can add around 10% to the costs of a development project, especially if soil is considered contaminated and subject to additional removal fees. Indeed, a spraying programme on a development site is estimated to be £27.19 per m² (approximately US $54 per m²), and including finance costs this almost doubles to £50.88 per m² (approximately US $100 per m²) if soil has to be removed and clean soil imported and compacted (Child and Wade, 2000).
It is present by roads and railways, and stem debris may impede water flow in smaller water courses.
Environmental ImpactTop of page
Impact on Habitats
Threatened SpeciesTop of page
|Threatened Species||Conservation Status||Where Threatened||Mechanism||References||Notes|
|Myricaria germanica||EN (IUCN red list: Endangered) EN (IUCN red list: Endangered); No details No details|
Social ImpactTop of page
As mentioned in the Economic impact section, it may be considered unsightly and intrusive in amenity and other public spaces. In the UK, the constant barrage of publicity in the press (much of it ill-considered i.e. ‘can grow through concrete’) has given members of the public the impression that this is some sort of indestructible Triffid, and that once spotted in a garden it won’t be long before it is found growing up between the floorboards.
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Highly adaptable to different environments
- Is a habitat generalist
- Long lived
- Fast growing
- Reproduces asexually
- Has high genetic variability
- Damaged ecosystem services
- Ecosystem change/ habitat alteration
- Infrastructure damage
- Modification of hydrology
- Modification of successional patterns
- Monoculture formation
- Negatively impacts tourism
- Reduced amenity values
- Reduced native biodiversity
- Threat to/ loss of endangered species
- Threat to/ loss of native species
- Competition - monopolizing resources
- Competition - shading
- Rapid growth
- Difficult/costly to control
UsesTop of page
Uses ListTop of page
Animal feed, fodder, forage
- Erosion control or dune stabilization
Human food and beverage
- Emergency (famine) food
DiagnosisTop of page
It is most likely to be mistaken for either of its parents Fallopia japonica and Fallopia sachalinensis. Identification is on the basis of leaf shape and the characteristic intermediate leaf hairs found on the lower epidermis of the leaves. For both of these characters, it is important that only large fully-expanded stem leaves are examined. The male-fertile clones are particularly easy to distinguish from F. japonica var. japonica. Clear characters for distinguishing the three taxa may be found in Bailey et al. (1996, 2008), Zika and Jacobson (2003) and Botta-Dukát and Balogh (2008).
It is possible to eradicate knotweed if a new infestation of rhizome is spotted quickly and the resultant plants pulled or treated before the roots have become well established.
There has been little success with eradication policies for F. japonica, but given the smaller population size, it is perhaps a realistic and worthwhile aspiration; although there is some evidence that it is more difficult to eradicate (Bimova et al., 2003), and contains greater reserves of genetic diversity than the clone of F. japonica var. japonica. Also see Child (1999), and Child and Wade (2000).
Detection and InspectionTop of page
The UK Environment Agency have produced a Code of Practice, and the Cornwall and Devon Knotweed Forum have produced an excellent guide, which has advice on identifying the plant in the field at various stages of the season.
Similarities to Other Species/ConditionsTop of page
As a hybrid between Fallopia japonica and Fallopia sachalinensis it obviously shares many similarities with these plants. It should be noted that the tetraploid F. x bohemica is a cross between the dwarf montane F. japonica var. compacta and F. sachalinensis. The standard 6x and the rarer 8x F. x bohemica are both crosses between the F. japonica var. japonica clone and F. sachalinensis. The tetraploid and octoploid contain half japonica and half sachalinensis chromosomes, whereas the 6x is 66% japonica and 33% sachalinensis. This is reflected in their morphology; although they cannot currently be distinguished morphologically. It is also possible that the montane var. compacta component of the 4x may pre-adapt it to different habitats, because in the wild it is found up to 2500 m.a.s.l. (Bailey, 2003).
Prevention and ControlTop of page
F. japonica appears on the UK Wildlife and Countryside Act (1981) and as such it is illegal to cause the plant to grow in the wild. It is listed as a noxious weed in many states and provinces of North America and appears on many weed lists around the world. F. x bohemica is not such a well-recognised taxon, but the same conditions apply to its treatment.
Vehicles should be inspected when moving from infected sites to new ones.
Due to a large and persistent rhizome system, F. japonica is highly resistant to control efforts (Ainsworth et al., 2002), and the same also applies to F. x bohemica. The effectiveness of control and eradication interventions has recently been reviewed thoroughly by Kabat et al. (2006), who included 65 articles in their meta-analysis. Six categories of intervention were included, none of which could eradicate Japanese knotweed or its hybrid in the short term. Cutting treatments alone were not found to result in significant decreases in knotweed abundance. However, statistically-significant reductions in abundance can be achieved by short-term application of: glyphosate; imazapyr; imazapyr and glyphosate; cutting followed by filling stems with glyphosate; and cutting followed by spraying with glyphosate (Kabat et al., 2006). However, these authors were still unable to conclude long-term efficacy for any control measure.
Mechanical control of F. japonica is difficult, but continual mowing will reduce the resources of the extensive rhizome system if carried out throughout the growing season. Glasshouse trials have shown that repeated cutting at least every 4 weeks and at least 7 weeks prior to senescence, can be effective (Seiger and Merchant, 1997). Pulling up plants complete with root systems can eliminate small stands and is appropriate for local eradication in sensitive areas, but only if carried out continually over a number of years (Baker, 1988). However, digging up roots is even more challenging because they can extend to a depth of 2 m, and 7 m away from the crown, and despite the best efforts, this normally results in an increased stem density. This may be useful for integrated control. With its Fallopia sachalinensis component, F. x bohemica may be slightly more palatable for stock. Certainly F. sachalinensis was promoted as fodder for livestock in the early 1900s (Bailey and Conolly, 2000).
Much work has been done on F. japonica at CABI Biosciences (Shaw et al., 2009), but this was mainly based on the European clone of F. japonica, and the aim was to obtain agents specific to that clone. The F. japonica programme has been underway, on behalf of UK and North American sponsors, since May 2003, with two candidate agents, namely a Mycosphaerella leafspot and the psyllid Aphalara itadori. Both of these agents have undergone extensive host range testing and have good potential as biological control agents. Given the difficulty faced by property developers, there would appear to be a market for a mycoherbicide, although registration costs are hindering this approach. As a newly arisen hybrid it is doubtful that any specialist predators actually exist for F. x bohemica and it will be a matter of selecting agents that are restricted to F. japonica and F. sachalinensis.
For F. japonica, chemicals that are permitted on or near water are normally restricted as will be the potential for full control. Child and Wade (2000) recommended five herbicides for F. japonica control, to be applied as foliar sprays. Triclopyr and imazapyr can be applied to young, actively-growing shoots when grasslands need to be protected; glyphosate is suitable during active growth periods when leaves are fully expanded, although larger plants may need to be sprayed using a telescopic/long lance sprayer; picloram can also be used as a soil drench due to its persistence, but not where planting is required within 2 years; and 2,4-D amine is used during the active growing period and as a selective translocated herbicide to be used in grassland, amenity areas and forest situations, although this may depend on which formulation is used in which country. Of the five herbicides, only glyphosate and 2,4-D amine can be used near water. In general, cutting and removing dead stems at the end of the season, prior to a spraying regime the following season, is advisable to aid access. F. japonica is a very resilient plant and unless extremely toxic chemicals are appropriate, repeated well-timed applications should be anticipated, and follow-up spot treatments of any regrowth will often be required.
Stem injection of various herbicides is a relatively modern phenomenon and can produce very good results in some conditions, but concerns remain over the amount of chemical that is actually applied per hectare exceeding statutory maxima. Hagen and Dunwiddie (2008) discovered that using glyphosate, through the injection method, results in the short-term dieback of injected stems. However, drawbacks to its use in certain scenarios should be considered when developing an integrated management plan for knotweed control.
Much of the above will also apply to F. x bohemica, although the larger leaf area and the fact that chemical control is more difficult with F. x bohemica (Bimova et al., 2003), may point to the need for some experimentation with the dosage used and the times and frequency of application.
For F. japonica the use of a combination of mechanical and chemical techniques has proved effective, i.e. cutting and a follow-up spray of new growth, but it is necessary to apply the chemical more than once a season (de Waal, 1995). There are two basic methods: to cut plants to 5 cm height and immediately apply a 25% solution of glyphosate or triclopyr to the cut stems; or cut or mow infestations when the plants reach the early bud stage in the late spring or summer and treat the regrowth in the autumn with glyphosate or triclopyr. If deep digging is used to effectively increase the above ground:below ground biomass ratio, then subsequent chemical application can reduce the time required to achieve effective control (Child et al., 1998). Another herbicide strategy is an integrated strategy with mowing or cutting.
Similar approaches for F. x bohemica should be attempted in order to assess their effectiveness.
Monitoring and Surveillance
There are various GIS surveys on-going in the UK, the first being in Swansea, followed by Cornwall and Devon. Professor Denis Murphy and Daniel Jones at the University of Glamorgan are currently working in this area. Whilst it is highly unlikely that the system would ever be able to discriminate between the different knotweed taxa, it is nevertheless a powerful tool for charting the distribution and extent of this group.
Rapid eradication of F. x bohemica is only possible if rhizome growth has not been too extensive.
F. japonica is able to hyper-accumulate heavy metals, including copper, zinc and cadmium, more effectively than other angiosperm species as has been demonstrated in Japan (Nishizono et al., 1989) and Croatia (Hulina and Dumija, 1999). However, the abilities of F. x bohemica in this direction remain untested.
Gaps in Knowledge/Research NeedsTop of page
Do the Wildlife and Countryside Act and subsequent Duty of Care regulations actually apply to the hybrid F. x bohemica and if not the appropriate legislative changes should be made?
ReferencesTop of page
Adolphi K, 1999. First record of Fallopia x bohemica (Chrtek & Chrtkova) J. Bailey in the Netherlands. (De eerste vondst van Fallopia x bohemica (Chrtek and Chrtkova) J. Bailey in Nederland.) Gorteria, 25:140-142.
Bailey J, 2003. Japanese Knotweed s.l. at home and abroad. In: Plant invasions: ecological threats and management solutions [ed. by Child, L.\Brock, J. H.\Brundu, G.\Prach, K.\Pyse?k, K.\Wade, P. M.\Williamson, M.]. Leiden, Netherlands: Backhuys Publishers, 183-196.
Bailey JP, 1994. Reproductive biology and fertility of Fallopia japonica (Japanese knotweed) and its hybrids in the British Isles. In: Ecology and management of invasive riverside plants [ed. by Waal, L.C. de\Child, L.E.\Wade, P.M.\Brock, J.H.]. Chichester, UK: John Wiley & Sons Ltd, 141-158.
Balogh L, 1998. Exomorphological observations in support of the presence of the hybrid species Fallopia x bohemica in Hungary. (Külsõ alaktani megfigyelések a Fallopia x bohemica (Chrtek & Chrtková) J. Bailey (F. japonica x F. sachalinensis) hibridfaj magyarországi jelenlétének alátámasztásához.) Kitaibelia (Debrecen), 3(2):255-256.
Balogh L, 2003. Species of the genus Fallopia sectio Reynoutria in Hungary - a land of the hybrid Fallopia x bohemica? In: Invasive Plants in Natural and Managed Systems: Linking Science and Management and 7th International Conference on the Ecology and Management of Alien Plant Invasions, Wyndham Bonaventure Resort, Ft. Lauderdale, Forida, USA, November 3-7, 2003. 7.
Child L; Wade M, 2000. The Japanese knotweed manual: the management and control of an invasive alien weed. The Japanese knotweed manual: the management and control of an invasive alien weed, xi + 123 pp.
Eliás P, 2001. [English title not available]. (Dva naturalizovaNé neofyty [Sarcoca esculenta (van Houtte) skalicky a Fallopia x bohemica (Chrtek et Chrtková) J.P.Bailey v meste trnave.) Acta Fac. Paed. Univ. Tyrnaviensis, Ser. B, 5:13-21.
EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm
Fehér A, 1999. Reconstruction of the spread of invasive species of Fallopia genus in Pozitavska pahorkatina region. In: Invasions and invasive organisms [ed. by Elias, P.]. Bratislava-Nitra, Slovakia: SNK Scope & Sekos, 96-103.
Fojcik B; Tokarska-Guzik B, 2000. Reynoutria x bohemica (Polygonaceae): a new taxon to the Polish flora. (Reynoutria x bohemica (Polygonaceae): nowy takson we florze Polski.) Fragm. Flor. Geobot. Polon, 7:63-71.
Galasso G; Banfi E; Mattia FDe; Grassi F; Sgorbati S; Labra M, 2009. Molecular phylogeny of Polygonum L. (Polygonoideae, Polygonaceae), focusing on European taxa: preliminary results and systematic considerations based on rbcL plastidial sequence data. Atti della Società italiana di scienze naturali e del Museo civico di storia naturale di Milano, 150(1):113-148.
Gammon MA; Grimsby JL; Tsirelson D; Kesseli R, 2007. Molecular and morphological evidence reveals introgressions in swarms of the invasive taxa Fallopia japonica, F. sachalinensis, and F. × bohemica (Polygonaceae) in the United States. American Journal of Botany, 94:948-956.
Gillespie P; Faithfull I, 2004. Knotweed: state prohibited weed. Knotweed: state prohibited weed. Victoria, Australia: Department of Primary Industries. http://www.dpi.vic.gov.au/dpi/nreninf.nsf/LinkView/643CD116260B0928CA256E9000824464663C5274163D2336CA256E8D001EFC6C
Hollingsworth ML; Bailey JP; Hollingsworth PM; Ferris C, 1999. Chloroplast DNA variation and hybridisation between invasive populations of Japanese Knotweed and Giant Knotweed (Fallopia, Polygonaceae). Bot. J. Lin. Soc, 129:139-154.
Hollingsworth ML; Hollingsworth PM; Jenkins GI; Bailey JP; Ferris C, 1998. The use of molecular markers to study patterns of genotypic diversity in some invasive alien Fallopia spp. (Polygonaceae). Molecular Ecology, 7(12):1681-1691.
Kim JY; Park CW, 2000. Morphological and Chromosomal variation in Fallopia section Reynoutria (Polygonaceae) in Korea. Brittonia, 52:34-48.
Padula M; Lastrucci L; Fiorini G; Galasso G; Zoccola A; Quilghini G, 2008. [English title not available]. (Prime segnalazioni di Reynoutria x bohemica Chrtek & Chrtkova (Polygonaceae) per l'Italia e analisi dell distribuzione del genere Reynoutria Houtt.) Atti Soc. It. Sci. nat. Museo civ. Stor. Nat Milano, 149:77-108.
Pashley CH; Bailey JP; Ferris C, 2003. Further evidence of the role of Dolgellau, Wales, in the production and dispersal of Japanese Knotweed s.l. In: Plant invasions: ecological threats and management solutions [ed. by Child, L.\Brock, J. H.\Brundu, G.\Prach, K.\Pyse?k, K.\Wade, P. M.\Williamson, M.]. Leiden, Netherlands: Backhuys Publishers, 197-211.
Preston CD; Pearman DA; Dines TD, 2002. New atlas of the British and Irish flora. An atlas of the vascular plants of Britain, Ireland, the Isle of Man and the Channel Islands. Oxford, UK: Oxford University Press, xi + 910 pp.
Pysek P; Brock JH; Bímová K; Mandák B; Jarosík V; Koukolíková I; Pergl J; Stepánek J, 2003. Vegetative regeneration in invasive Reynoutria (Polygonaceae) taxa: the determinant of invasibility at the genotype level. American Journal of Botany, 90(10):1487-1495.
Richards CL; Walls RL; Bailey JP; Parameswaran R; George T; Pigliucci M, 2008. Plasticity in salt tolerance traits allows for invasion of novel habitat by Japanese knotweed s. l. (Fallopia japonica and F. × bohemica, Polygonaceae). American Journal of Botany, 95(8):931-942. http://www.amjbot.org/
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07/07/09 Original text by:
John Bailey, University of Leicester, UK
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