Myriophyllum heterophyllum Michx.

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English Various-leaved water-milfoil Status LU: absent. 1st record: n/a.
Lëtzebuergesch Wiesselblat-Waassergras Status Eur.: established. 1st record: DE 1960s. 1 IAS of EU 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 5457876Myriophyllum 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).

IAS of Union concern

In 2017, Myriophyllum heterophyllum Michx. was added to the list of invasive alien species of Union concern (Anonymous 2017) which implies that member states shall take all necessary steps to prevent it’s unintentional introduction or spread.

Status and distribution in Luxembourg

Myriophyllum heterophyllum Michx. has not yet been observed in Luxembourg (MNHNL, iNaturalist & GBIF 2020).

Risk assessment

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).


Worldwide distribution


  • Anonymous, 2017. Commission implementing regulation (EU) 2017/1263 of 12 July 2017 updating the list of invasive alien species of Union concern established by Implementing Regulation (EU) 2016/1141 pursuant to Regulation (EU) No 1143/2014 of the European Parliament and of the Council. Official Journal of the European Union L 182: 37-39 (13.7.2017).
  • 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]
  • CABI, 2021. Myriophyllum heterophyllum. In: Invasive Species Compendium. Wallingford, UK: CAB International. URL: [accessed 2021-03-04]
  • MNHNL, iNaturalist & GBIF, 2020. Myriophyllum heterophyllum in MNHNL-mdata, online portal combining species observation from Recorder-Lux, iNaturalist and GBIF. National Museum of Natural History, Luxembourg. URL: [Accessed 2020-03-02]
  • 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 2021-03-04. Last proofread by Caroline Grounds on 2019-11-20.