Egeria densa Planch.

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English Large-flowered waterweed Status LU: established. 1st record: LU & ITW 2016.
Lëtzebuergesch Dichtbliedreg Waasserpescht Status Eur.: established. 1st record: unkn.
Français Égérie dense RA: ISEIA: A1 – Black List. Harmonia+: 0,32
Deutsch Dichtblättrige Wasserpest Wikipedia: Wikipedia - English - Large-flowered waterweed Wikipedia - Deutsch - Dichtblättrige Wasserpest Wikipedia - Nederlands - Egeria (plant) | Wikispecies: Wikispecies - Egeria densa | CABI
Nederlands Egeria (plant) Back to the list of neophytes

Report the species

Report Egeria densa to the National Museum of Natural History.

Brief description

Egeria densa Planch. is a South American aquatic plant with a very wide ecological amplitude. It thrives in a variety of freshwater habitats: while it prefers flowing systems it may also be found in still waters. The species is not light-demanding and is able to develop in deep and turbid waters. The submerged perennial makes dense monospecific populations which often colonise whole water bodies, restrict water movement, cut off light, produce anoxic conditions and trap sediments in the system. The large-flowered water weed has been reported to outcompete native aquatic plants and to adversely affect fish communities (Branquart et al. 2013).

Status and distribution in Luxembourg

Records of Egeria densa Planch. in Luxembourg. Data source: Recorder-Lux, iNaturalist & GBIF, 2024-07-14.

Egeria densa Planch. was observed twice in 2016 in the Eisch valley East of Hobscheid ( and in 2019 in Luxembourg City (MNHNL, iNaturalist & GBIF 2019).

Risk assessment

ISEIA protocol

A1 (2+3+3+3) = Black List. Updated on 22 June 2018 by Christian Ries and Manou Pfeiffenschneider. Former assessment: A0 (2+3+3+3) = Alert List (Ries et al. 2013: 18).

Harmonia+ protocol

Overall risk score 0,32 = (Overall Invasion score 0,53 x Overall Impact score 0,62) (Ries et al. 2020).


Worldwide distribution


  • Branquart, E., I. Stiers, L. Triest, S. Vanderhoeven, W. Van Landuyt, F. Van Rossum & F. Verloove, 2013. Harmonia database: . Harmonia version 1.2, Belgian Forum on Invasive Species. URL: [accessed on 2020-02-28]
  • CABI, 2019. Egeria densa. In: Invasive Species Compendium. Wallingford, UK: CAB International. URL: [accessed 2020-02-28]
  • MNHNL, iNaturalist & GBIF, 2019. Egeria densa in MNHNL-mdata, online portal combining species observation from Recorder-Lux, iNaturalist and GBIF. National Museum of Natural History, Luxembourg. URL: [Accessed 2020-02-28]
  • Oly, M., 2022. Kartierung invasiver gebietsfremder Wasserpflanzen im Großherzotum Luxemburg, Untersuchungen zur Verbreitung von invasiven gebietsfremden Wasserpflanzen in einer beispielhaften Auswahl an Stillgewässern, Musée national d’histoire naturelle, Luxembourg. 117 pp. 
  • Ries, C. & Y. Krippel, 2021. First records of 56 invasive alien vascular plants in Luxembourg. Bulletin de la Société des naturalistes luxembourgeois 123: 115-127. [PDF 241 KB]
  • Ries, C., Y. Krippel & M. Pfeiffenschneider, 2020. Risk assessment after the Harmonia+ protocol of invasive alien vascular plant species in Luxembourg. Bull. Soc. Nat. luxemb. 122: 197-205. [PDF 132 KB]
  • 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 2023-08-17. Last proofread by Caroline Grounds on 2019-11-14.