Crassula helmsii New Zealand Pygmyweed DD I
This introduction from Australia or New Zealand (and also known as Australian Swamp Stonecrop) is believed to have come from vegetation thrown out by home aquarium owners. It has become a nuisance plant creating dense mats of vegetation on the surface of ponds and along the edges in the mud. C helmsii can be so prolific as to look like dry land which creates a danger for children and pets. In winter it doesn't die back very much so once established it tend to increase year on year.
C. helmsii is one of those plants which has created quite a fuss in the botanical world because of its invasive properties but it hasn't spread perhaps as far as people might think. It is found very often in the south east and north west of England and elsewhere in Wales and England it is quite common. However, naturalised colonies are far less commonly recorded in the far north of England, Scotland and Ireland where it is uncommon.
Pond Near Rudheath, Cheshire 3rd September 2005
Added on 3rd September 2005, updated 8th December 2008, updated 21st March 2010, updated Se3 4th May 2010