23/06/2026
🌿 Invasive Species Week: Crassula helmsii 🌿
Norfolk is home to an incredible number of ponds and a fantastic diversity of wildfowl, particularly along our beautiful coastline. These ponds and wetlands are some of our most important habitats, but they face a growing threat from invasive non-native species.
One of the most problematic is Crassula helmsii (also known as Australian Swamp Stonecrop or New Zealand Pygmyweed).
Originally introduced from New Zealand and Australia in the 1950s as a garden plant, the first naturalised record in Britain was made in Essex by the Botanical Society of Britain and Ireland (BSBI). Thanks to our mild climate and abundance of freshwater, this species thrives in the UK. Our beautiful wildflowl can accidently spread from site to site (as can humans so check and clean your wellies!!!)
Unfortunately, Crassula helmsii can rapidly outcompete our native wetland plants, reducing biodiversity and altering valuable pond habitats. As we get more drought conditions, this is one of the species that will thrive.
In recent years, volunteers and staff from the Norfolk Ponds Project have been working hard to tackle infestations of Crassula helmsii in ponds across Norfolk before it spreads across all our waterbodies.
🔍 How can you help?
Learn to identify it and send us photographs and locations of any sightings.
Crassula helmsii is usually easy to spot:
• It forms low-growing, dense mats of lush green vegetation.
• From a distance it can look a little like grass.
• Up close, it has pairs of opposite leaves along the stem.
• The leaves are succulent, feeling firm and sturdy.
• This helps distinguish it from some native water-starwort species, which are often softer and more delicate.
📸 If you think you’ve found Crassula helmsii, send us a photo and location using what3words or a grid reference.
Our Norfolk Ponds Project guide to identifying Crassula helmsii will be available soon – watch this space!
