Controlling Crassula helmsii

Research into controlling Crassula helmsii in the New Forest

New Zealand pigmyweed (Crassula helmsii)

New Zealand pigmyweed is a non-native invasive pond plant which has both emergent and submerged grow forms. It can grow in water up to 3 meters deep and on the pond margin some distance from the water. Under certain conditions it grows in thick mats which dominate the plant community and may pose a threat to our native species. It can also regenerate from as little as a 2 mm fragment of stem which makes it very easy to transfer it between ponds. Once in a pond it’s regenerative abilities make it incredibly difficult to control.

What we can try to do:

  • Prevent the spread of all non-native plants between ponds by following the check, clean, dry advice
  • Better understand the impact New Zealand pigmyweed can have on native plants and animals
  • Identify which ponds are under greatest risk
  • Monitor the effects of control methods on New Zealand pigmyweed to determine how effective they are and what impact they have on non-target plants and animals

Freshwater Habitats Trust – with funding from Hampshire and Isle of Wight Wildlife Trust’s New Forest non-native plants project – looked at some of the novel techniques trialed to control New Zealand pigmyweed. Find out more.

We would like to hear of your experiences with New Zealand pigmyweed and attempts to control it: