Lemna minuta Humb., Bonpl. et Kunth

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English Least duckweed Status LU: casual. 1st record: 2002.
Lëtzebuergesch Klinzeg Intelëns Status EU: established.
Français Lentille d’eau minuscule RA: ISEIA: B1, Watch List. Harmonia+: 0,24.
Deutsch Winzige Wasserlinse Wikipedia: Wikipedia - English - Least duckweed Wikipedia - Nederlands - Dwergkroos Deutsch | Wikispecies: Wikispecies - Lemna minuta | CABI
Nederlands Dwergkroos Back to the list of neophytes

Report the species

Report Lemna minuta to the National Museum of Natural History.

Brief description

Lemna minor & minuta PG

Mixed stand of Lemna minor (large leaves) and Lemna minuta (small leaves, more transparent).

Lemna minuta Humb., Bonpl. et Kunth is an aquatic plant that settles in shallow standing or slow-flowing waters, often in shaded conditions. Outbreaks of the species cause dense floating mats at the water surface that reduce light penetration and gas exchanges, causing the predominance of respiratory activities and the reduction in dissolved oxygen in water beneath the mats. As for native duckweed species, outbreaks are usually limited in time and space and are favoured by increased levels of water eutrophication that often cause the disappearance of submerged macrophytes. Waterfowl and Cyprinid fish are known to eat duckweeds to supplement their diet which may help to reduce outbreaks (Branquart et al. 2010).

Status and distribution in Luxembourg

Records of Lemna minuta Humb., Bonpl. et Kunth in Luxembourg. Data source: Recorder-Lux, iNaturalist & GBIF, 2020-07-07.

Lemna minuta Humb., Bonpl. et Kunth was first documented in Mecheren near Remerschen (Municipality of Schengen) close to the bird watch station on 21 June 2015 by Guy Colling and on 29 June 2015 by A. Mesterházy (Krippel & Colling 2016: 39; MNHNL 2000-). It should be noted that the tiny water lens had already been reported for the Remerschen ponds in 2002 by Gérard Schmidt (in litt.), but no herbarium specimens had been taken at that time (Krippel & Colling 2016: 39).

3 records of the species are listed in the MNHNL-mdata online portal (MNHNL, iNaturalist & GBIF 2019).

This American aquatic monocotyledon, the smallest species of its kind (Synonym: Lemna minuscula Herter), was discovered in the wild here in 1983 (Lambinon & Verloove 2012: 976). Given its pervasive potential, it was listed on the alert list (Ries et al. 2013).

Risk assessment

ISEIA protocol

B1 (2+3+2+3) = Watch List. Reassessed 16 February 2017 by Yves Krippel and Christian Ries. Assessment before the appearance of the species in Luxembourg: B0 (2+3+2+3) = Alert List (Ries et al. 2013).

Harmonia+ protocol

Overall risk score 0,24 = (Overall Invasion score 0,67 x Overall Impact score 0,35) (Ries et al. 2020).


Worldwide distribution


  • Branquart, E., I. Stiers, L. Triest, S. Vanderhoeven, W. Van Landuyt, F. Van Rossum & F. Verloove, 2010. Harmonia database: Lemna minuta Humb., Bonpl. et Kunth. Harmonia version 1.2, Belgian Forum on Invasive Species. URL: http://ias.biodiversity.be [accessed on 2019-10-11]
  • CABI, 2019. Lemna minuta. In: Invasive Species Compendium. Wallingford, UK: CAB International. URL: www.cabi.org/isc [accessed 2020-03-02]
  • Krippel, Y. & G. Colling, 2016. Notes floristiques. Observations faites au Luxembourg (2014-2015). Bull. Soc. Nat. luxemb. 118: 27-51. [PDF 1,33 MB]
  • 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-. Lemna minuta Humb., Bonpl. et Kunth 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 2019-10-11]
  • MNHNL, iNaturalist & GBIF, 2019. Lemna minuta Humb., Bonpl. et Kunth in MNHNL-mdata, online portal combining species observation from Recorder-Lux, iNaturalist and GBIF. National Museum of Natural History, Luxembourg. URL: https://mdata.mnhn.lu [Accessed 2019-10-11]
  • Ries, C., Y. Krippel & M. Pfeiffenschneider, 2020 [submitted]. Risk assessment after the Harmonia+ protocol of invasive alien vascular plant species in Luxembourg. Bulletin de la Société des naturalistes luxembourgeois.
  • 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]

 Page content last updated on 2020-04-29. Last proofread by Caroline Grounds on 2019-11-19.