Research output

Reproduction of Crassula helmsii by seed in western Europe

Research output: Contribution to journalA1: Web of Science-article


External Organisations

  • Biology Department, Ghent University, K.L. Ledeganckstraat 35, 9000 Ghent, Belgium
  • Netherlands Food and Consumer Safety Authority, P.O. Box 9102, 6700 HC Wageningen, The Netherlands


Original languageEnglish
JournalAquatic Invasions
Issue number2
Pages (from-to)125–130
Publication statusPublished - 2016


The amphibious plant species Crassula helmsii is a widely established and still-spreading alien in various parts of Europe, where it is considered invasive as its dense swards stress the viability of local biota. The species was considered to exclusively reproduce through vegetative means, until
ex situ germination was recorded from a single locality in Belgium. We assessed whether this seed viability holds on a wider scale, by testing 16 populations from The Netherlands, Belgium, northern France, eastern England and northern Germany in a greenhouse germination experiment. Seedlings were observed from all populations but two, and from each of the five countries. Although most fruits were lacking seeds and the inferred germination percentages were overall low, germinable seed numbers are considerable given the high density of flowering stems. An in situ test revealed seeds to make it through normal winter conditions without signs of physical damage and with retention of germinability. Our results suggest that reproduction by seed is a relatively cryptic but widespread phenomenon throughout western Europe. The persistency of seed banks requires further investigation. Nonetheless, these findings already challenge the efficacy of techniques currently applied in C. helmsii control.

Thematic List 2020

EWI Biomedical sciences

Taxonomic list

Free keywords

  • invasive alien species, invasive species
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