Crassula helmsii

(also known as swamp stonecrop or New Zealand pigmyweed)
Status: Non-native, invasive

It is now banned from sale (since 2014)

What's the problem?

Around the edges in shallow water it forms dense, impenetrable mats, and it can even grow in the open on damp mud around seasonal pools. In the ponds it can destroys all other life . Just a tiny fragment of the stem can regrow and multiply into a dense mat of vegetation.

It is a Critical Risk

This species is also listed on Schedule 9 of the Wildlife and Countryside Act in England and Wales. Therefore, it is also an offence to plant or otherwise cause to grow these species in the wild.

Removing - early and regular treatment is highly recommended. In small ponds, regular digging out of the plant may be an effective control technique, but care needs to be taken as small fragments can disperse and regenerate.