Australian Swamp Stonecrop (Crassula helmsii)

Species

Distribution


Australian swamp stonecrop
(Crassula helmsii)

Photo courtesy of GB Non Native Species Secretariat


To view NBN location data click here

Impacts

Pathways
  • Suited to a wide range of slow moving freshwater systems.
  • Out competes native species.
  • Forms dense carpets choking ponds and ditches.
  • Reduced light levels below the rafts can cause die off of waterweeds and algae and reduce water oxygenation levels
  • Sold in Garden Centres and/or aquarium trade.
  • Disposal or escape into the wild from private gardens.
  • Secondary spread by animals and human activity from an infested site to new sites may occur.

Management

Prevention

Should not be released in the wild. Dispose of garden and pond waste responsibily. Check vehicles, boats, equipment and clothing for plant fragments when leaving infested sites and clean if necessary.

Mechanical Control and Physical Removal

Mechanical control is NOT recommended as it can result in small viable fragments being left in the water, which may spread the plant downstream or elsewhere within moving waterbodies,  lakes and reservoirs. However, physical removal may be practical for small water-bodies. Shading out with dark-plastic sheeting has been successful (DAISIE).

Chemical Control

Has been shown to be resistant to many available herbicides. Efficacy depends of the density of the plants to be managed and water temperature. Application of diquat is most effective in the autumn and winter with water temperatures >12°C, below 8°C absorption is poor. For emergent plants glycophosphate may be used but more than one application may be needed spaced about three weeks apart. In small enclosed waterbodies physical removal followed by chemical treatments using diquat has been shown to be effective. Complete eradication is often difficult. More information on control measures is avaiable from the Centre for Ecology and Hydrology, Centre for Aquatic Plant Management Information Sheet 11 (Click here to download)

Note all chemical treatments must be licensed by SEPA.

Biological Control

None

Links
Non Native Species Secretariat identification guide

Non Native Species Secretariat Fact Sheet

SNH Species Action Framework also see SNH SAF Training Manual

Daisie Species Fact Sheets

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