Extra aandacht voor Watercrassula (Crassula helmsii (Kirk) Cockayne)

In 2001 and 2002, Crassula helmsii has been found on three locations in the eastern part of the Netherlands in artificial ponds. After its fast spreading throughout Great Britain, this alien aquatic plant now seems to be colonizing continental Europe. Its dispersal is a combination of humaninitiated primary invasion and secondary spreading of plants through vegetative mechanisms. This publication contains a list of taxonomic details and a short description of the newly occupied habitats. A weed warning is given for this species.