Fallopia japonica (Houtt.) Ronse Decr.

English Japanese knotweed ISEIA: A3 – Black List
Lëtzebuergesch Japanescht Knuetkraut EASIN
Français Renouée du Japon, renouée bambou Wikipedia: Wikipedia - English - Japanese knotweed Wikipedia - Français - Renouée du Japon Wikipedia - Deutsch - Japanischer Staudenknöterich Wikipedia - Nederlands - Japanse duizendknoop  Wikipedia - Português - Fallopia
Deutsch Japanischer Staudenknöterich, J. Flügelknöterich Wikispecies: Wikispecies - Japanese knotweed
Nederlands Japanse duizendknoop Back to the list of neophytes

Report the species

Report Fallopia japonica to the National Museum of Natural History.

Importance and distribution in Luxembourg

Distribution map of Fallopia japonica (Houtt.) Ronse Decr. in Luxembourg. Data source: Recorder-Lux & iNaturalist, 2019-09-21.

According to Eugène Fischer (1821-1903), Fallopia japonica was introduced in Luxembourg around 1852 (Fischer 1872: 89). He lists the species under its synonym Polygonum cuspidatum Sieb. 1 Some twenty years after its introduction, Fischer already has a feeling of the potential of this species as an invasive species: “Siebold’s knotweed […], originating from Japan, was introduced into ornamental crops in the Grand Duchy around 1852. It is very tractable, remarkable for its great development and its great rusticity which allows it to grow in all terrains and at all exhibitions. It multiplies and is maintained with such ease that it returns without culture and care to some gardens and nearby. I am inclined to believe that it will now remain in the country as a subspontaneous plant.” 2

The first documented observation of the species in Luxembourg dates from 1947. François Léon Lefort collected on 11th July 1947 a specimen near the Carmel in Luxembourg City (Specimen № 22229, MNHNL 2000-).

According to Lambinon & Verloove (2012: 193), the species occurs on wasteland, embankments, stream banks, forest edges. Sometimes grown for ornamental purposes in parks (formerly also as fodder). Fairly common to fairly rare (AC-AR) and naturalized in all flora districts, very invasive.

Currently, 1.140 records of the species and its subspecies are accessible through the MNHNL-mdata portal (MNHNL & iNaturalist 2019).

Japanese knotweed is one of the most common and widespread invasive neophytes in Luxembourg. It builds huge colonies along riparian ecosystems, several major rivers of Luxembourg being affected. A worst case example can be seen along the river Sure between Ettelbruck and Michelau.

It is regularly found building smaller colonies along roadsides and in waste grounds, most of these places have been “contaminated” by people getting rid of knotweed clippings from their gardens. This can easily be seen along the main road leaving Luxembourg-City in the direction of Echternach.

Nurseries and garden designers sometimes contribute to the spread of Japanese knotweed in gardens and public green spaces by using contaminated compost.

Status of Fallopia japonica in Luxembourg

Until recently, Japanese knotweed was considered much more widespread in Luxembourg than its taller “cousin”, the Sakhalin knotweed (Fallopia sachalinensis).

As part of a study for the Department of Ecology section of the National Museum of Natural History, samples of 31 specimens of Fallopia species have been collected in 2017. The sampled specimens were described and leaves and stem parts were collected for integration in the museums herbarium. The samples have been subjected to genetic analysis by the museum’s lab. The results show that F. x bohemica is much more common than Fallopia japonica. The distribution data of both species need to be updated.

Japanese knotweed in a public green space at the entrance of the regional school in the municipality of Tandel. © 27.06.2006 by Christian Ries.

Risk assessment

ISEIA protocol: A3 (3+3+3+3) = Black List (Ries et al. 2013: 18). Needs to be reassessed (see above).

Bibliography concerning Luxembourg

  • Albers, M., S. Kohn, J. Steng & M. Pfeiffenschneider, 2001. – Problematik der Bioinvasion. Kartierung von Japan-Knöterich, Riesenbärenklau und Indischem Springkraut an Woltz, Clerve und Wiltz. Ergebnisse der Kartierung. – Studie des Büros ERSA im Auftrag von: Administration des eaux & forêts, arrondissement nord. August 2001. 7S. + Anhang.
  • Fischer, E., 1872. Les plantes subspontanées et naturalisées de la flore du grand-duché de Luxembourg. Publications de l’Institut royal grand-ducal de Luxembourg, section des sciences naturelles et mathématiques XII: 1-115. Imprimerie V. Buck, Luxembourg.
  • Glesener, B., M. Pfeiffenschneider & C. Ries, 2009. Die Verbreitung von Impatiens glandulifera, Fallopia japonica, F. sachalinensis, F. ×bohemica und Heracleum mantegazzianum entlang der Hauptfließgewässer Luxemburgs. Bull. Soc. Nat. luxemb. 110 : 69-73. (pdf)
  • Lambinon J. & F. Verloove, 2012. Nouvelle flore de la Belgique, du grand-duché de Luxembourg, du Nord de la France et des régions voisines. Sixième édition. Avec la collaboration de L. Delvosalle, B. Toussaint, D. Geerinck, I. Hoste, F. Van Rossum, B. Cornier, R. Schumacker, A. Vanderpoorten et H. Vannerom. Jardin botanique national de Belgique, Meise. CXXXIX + 1195 pp. ISBN : 9789072619884.
  • MNHNL, 2000-. Fallopia japonica (Houtt.) Ronse Decr. in Recorder-Lux, database on the natural heritage of the Grand Duchy of Luxembourg. Musée national d’histoire naturelle, Luxembourg. URL: https://mdata.mnhn.lu [Accessed 2019-09-05]
  • MNHNL & iNaturalist, 2019. Fallopia japonica (Houtt.) Ronse Decr. in MNHNL-mdata, online portal combining species observation from Recorder-Lux and iNaturalist. National Museum of Natural History, Luxembourg. URL: https://mdata.mnhn.lu [Accessed 2019-09-05]
  • Pfeiffenschneider, M., 2001. – Problematik der Bioinvasion. Nationales Inventar von Riesenbärenklau, Indischem Springkraut und exotischen Knötericharten. Ergebnisse einer Umfrage und Konzept zur Bekämpfung der Riesenbärenklaubestände. – Studie des Büros ERSA im Auftrag von: Administration des eaux & forêts, Service de la conservation de la nature, November 2001. 23 S. + Anhang, Luxembourg.
  • Pfeiffenschneider, M., 2007. Über die Verbreitung von Heracleum mantegazzianum, Impatiens glandulifera, Fallopia japonica und F. sachali­nensis entlang der Gewässer Obersauer, Woltz, Clerve, Wiltz und ihrer Nebengewässer (Luxemburg). Bull. Soc. Nat. luxemb. 108 : 7-10. (pdf)
  • Pfeiffenschneider, M., 2008. Neophyten in Luxemburg – Projekt Bioinvasion 2007. Arbeitsbericht. 18 S. (pdf)
  • Pfeiffenschneider, M. & M. Owaller, 2000. – Kartierung von Japan-Knöterich, Riesenbärenklau und Indischem Springkraut an der Obersauer. Theoretische Grundlagen und Ergebnisse der Kartierung. – Studie des Büros ERSA im Auftrag von: Administration des eaux & forêts, acrrondissement nord. August 2000. 37S. + Anhang, Luxembourg.
  • Ries, C., Y. Krippel, M. Pfeiffenschneider & S. Schneider, 2013. Environmental impact assessment and black, watch and alert list classification after the ISEIA Protocol of non-native vascular plant species in Luxembourg. Bull. Soc. Nat. luxemb. 114: 15-21. [PDF 652 KB]

Suggested citation of this webpage

Ries, C. & M. Pfeiffenschneider (Eds.), 2019. Fallopia japonica (Houtt.) Ronse Decr. In: neobiota.lu - Invasive Alien Species in Luxembourg. National Museum of Natural History, Luxembourg. URL: https://neobiota.lu/fallopia-japonica/ [Accessed 2019-09-21].

 Last updated on Friday, September 6, 2019.


  1. According to the Plants of the World online the correct/complete name of this synonym should be Polygonum cuspidatum Siebold & Zucc.
  2. Original text: « La renouée de Siebold […], originaire du Japon, a été introduite dans les cultures ornementales du Grand-Duché vers 1852. Elle est très traçante, remarquable par son grand développement et sa grande rusticité qui lui permet de croître dans tous les terrains et à toutes les expositions. On la voit se multiplier et se maintenir avec tant de facilités qu’elle revient sans culture et sans soins dans quelques jardins et à proximité. Je suis porté à croire qu’elle se maintiendra dorénavant dans le pays comme plante subspontanée. » (Fischer 1872: 89)