Crassula helmsii (Kirk) Cockayne

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English New Zealand pigmyweed ISEIA: B0 – Alert List
Lëtzebuergesch n/a EASIN
Français Crassule des étangs Wikipedia: Wikipedia - English - New Zealand pigmyweed Wikipedia - Deutsch - Nadelkraut Wikipedia - Nederlands - Watercrassula
Deutsch Nadelkraut Wikispecies: Wikispecies - Crassula helmsii
Nederlands Watercrassula Back to the list of neophytes

Report the species

Report Crassula helmsii to the National Museum of Natural History.

Status and distribution in Luxembourg

Currently, Crassula helmsii (Kirk) Cockayne is not known to occur in Luxembourg.

New Zealand pigmyweed is an aquatic or semi-terrestrial plant that colonises a wide variety of freshwater habitats. The plant’s ability to grow from stem fragments enables it to easily spread from ponds and ornamental pools into the wild. Waterfowl, mammals, downstream movement and flooding all play an important role in plant dissemination. The species can cause major environmental problems in freshwater habitats. It forms dense vegetation mats that deplete oxygen, outcompete native species and may affect the breeding success and survival of threatened aquatic plants and amphibians. Mats choke ponds and drainage ditches, impede water flow and adversely affect recreational activities. In rivers, flow behavior may change when the plant occurs in masses (Source:

Risk assessment

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


  • 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 2019-10-29.