Lagarosiphon major Ridl. Moss ex Wager

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English Curly waterweed Status LU: n/a. 1st record: n/a.
Lëtzebuergesch Gekréngelt Waasserpescht Status EU: established. IAS of Union concern (2016)
Français Elodée crépue RA: ISEIA: A0, Alert List. 
Deutsch Wechselblatt-Wasserpest Wikipedia: Wikipedia - English - Curly waterweed Wikipedia - Deutsch - Wechselblatt-Wasserpest | Wikispecies: Wikispecies - Lagarosiphon major
Nederlands Verspreidbladige waterpest Back to the list of neophytes

Report the species

Report Lagarosiphon major to the National Museum of Natural History.

Brief description

Lagarosiphon major Ridl. Moss ex Wager, Curly Waterweed, preferentially develops in clear, still or slow-flowing water systems. It can live in a wide range of trophic conditions providing that a silty or sandy bottom rich in nutrients is available. It prefers well-lit environments. The plant 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 species has been reported to outcompete native aquatic plants and to affect associated populations of aquatic invertebrates and vertebrates. Dense beds provide a poor habitat for aquatic animals and are not consumed by fish. They interfere with recreational activities and increase the risk of adjacent land flooding (Branquart et al. 2013).

Status and distribution in Luxembourg

Lagarosiphon major Ridl. Moss ex Wager has not yet been observed in Luxembourg.

Risk assessment

ISEIA protocol

A0 (2+3+3+3) = Alert List (Ries et al. 2013: 18).

Harmonia+ protocol

Overall risk score 0,39 = (Overall Invasion score 0,60 x Overall Impact score 0,65) (Ries et al. 2020).


  • Branquart, E., I. Stiers, L. Triest, S. Vanderhoeven, W. Van Landuyt, F. Van Rossum & F. Verloove, 2013. Harmonia database: Lagarosiphon major Ridl. Moss ex Wager. Harmonia version 1.2, Belgian Forum on Invasive Species. URL: [accessed on 2019-11-21]
  • 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]
  • 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.

 Page content last updated on 2020-01-24. Last proofread by Caroline Grounds on 2019-11-19.