Myriophyllum heterophyllum Michx.

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English Various-leaved water-milfoil Status LU: n/a. 1st record: n/a
Lëtzebuergesch Wiesselblat-Waassergras Status EU: established. IAS of Union concern (2017)
Français Myriophylle hétérophylle RA: ISEIA: B0 – Alert List. Harmonia+: 0,47
Deutsch Verschiedenblättriges Tausendblatt Wikipedia: Wikipedia - Français - Myriophylle hétérophylle Wikipedia - Deutsch - Verschiedenblättriges Tausendblatt | Wikispecies: Wikispecies - Myriophyllum heterophyllum | CABI
Nederlands Ongelijkbladig vederkruid Back to the list of neophytes

Report the species

Report Myriophyllum heterophyllum to the National Museum of Natural History.

Brief description

Myriophyllum heterophyllum Michx. grows in well-lit ponds, ditches, canals and slow-running streams. It is found growing under a wide range of chemical conditions, but tends to prefer acidic waters. Variable watermilfoil is able produce very dense populations and high biomass. It is highly competitive and may lead to the exclusion of other submerged water plants. The dense mats it produces reduce sunlight and can restrict water movement; when decomposing, they alter water quality and reduce available oxygen. The low oxygen conditions can kill fish and harm other aquatic organisms. The plant can also cause boating and swimming hazards (Baus et al. 2013).

Status and distribution in Luxembourg

Myriophyllum heterophyllum Michx. has not yet been observed in Luxembourg.

Risk assessment

ISEIA protocol

ISEIA protocol: B0 (2+3+2+3) = Alert List (Ries et al. 2013: 18).

Harmonia+ protocol

Overall risk score 0,47 = (Overall Invasion score 0,63 x Overall Impact score 0,75) (Ries et al. 2020).


  • Baus E., Branquart, E., I. Stiers, L. Triest, S. Vanderhoeven, W. Van Landuyt, F. Van Rossum & F. Verloove, 2013. Harmonia database: Myriophyllum heterophyllum Michx.. 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 2019-11-20.