Phragmites is an aggressive, fast-growing waterway and wetland pest. It’s one of nine harmful weeds on MPI’s National Interest Pest Response list because it can have devastating impacts on our wetland and estuary environment.
Phragmites is an aquatic perennial grass that grows up to 3m tall with bluish-green leaves which taper to a point.
It looks similar to bamboo, but there are some key differences. While bamboo has woody ringed stems and each bamboo leaf has its own stalk. Phragmites has softer, slim stems and each leaf attaches directly to the stem without a leaf stalk.
Phragmites thrives in damp ground alongside waterways, on estuary edges, and in wetlands. It quickly forms dense stands, and once established is very hard to eradicate.
Phragmites is an exclusion pest in our Regional Pest Management Plan. It is not known to exist in Tasman, but it could sneak in at any time. In 2023, shipping containers brought into Nelson from China were found to contain phragmites seeds. Several locations were exposed when the containers were distributed and opened at different sites.
Fortunately on discovery, quick action was taken to minimise the chance of the seeds spreading into the environment. Regular biosecurity surveillance at each site has so far yielded no germinated phragmites plants, so we are counting our lucky stars.
If you think you have seen phragmites in our region, please contact our Biosecurity team at biosecurity@tasman.govt.nz or give us a call on 03 543 8400. Let’s keep this highly damaging pest out of Tasman!