Conservation Evidence strives to be as useful to conservationists as possible. Please take our survey to help the team improve our resource.

Providing evidence to improve practice

Action: Crassula helmsii: Use a combination of control measures Control of Freshwater Invasive Species

Key messages

Read our guidance on Key messages before continuing

  • One before-and-after study at a single pond in the UK found covering Crassula helmsii with carpet, followed by treatment with the herbicide glyphosate, killed 80% of the plant.

Supporting evidence from individual studies


A before-and-after study in 2002-2003 at a single pond in Surrey, UK (Anonymous 2004) reported that covering C. helmsii with carpet strips followed by the application of glyphosate reduced the area of the plant, although no statistical tests were carried out. One year after glyphosate application approximately 80% of C. helmsii had been killed. In autumn 2002, strips of carpet were placed over C. helmsii and weighted down wherever possible on the pond edge and in shallow water. In July-August 2003 the carpet was removed and the glyphosate-based herbicide Roundup was applied twice.


Referenced papers

Please cite as:

Aldridge, D., Ockendon, N., Rocha, R., Smith, R.K. & Sutherland, W.J. (2019) Some aspects of control of freshwater invasive species. Pages 569-602 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.