About phragmites
Phragmites is a perennial grass found on water margins that grows up to 6 m tall. It has bamboo-like stems which carry long, wide, flat leaves that taper to a point. The flower is showy and silky, purple or white, up to 40 cm long, but it doesn’t set seed in New Zealand. It is spread accidentally by root or rhizome (underground root-like stems) fragments. It is similar to giant reed (Arundo donax), but phragmites is smaller and the stems are narrower in proportion to the leaves.
Why we don't want phragmites in New Zealand
Phragmites is considered the worst aquatic weed in New Zealand. In its native habitat, phragmites usually grows in dense stands, excluding other plants. If allowed to become more widespread in New Zealand, it could crowd out native plants and reduce the numbers of insects and birds in wetland habitats.
Phragmites has dense growth which dies back each winter and can be a fire risk. It also blocks drainage systems causing flooding, can invade low-lying pasture, and can block access to waterways, restricting fishing and boating.
Where phragmites has been found in NZ
Phragmites has only been found at a limited number of sites in Canterbury, Hawke’s Bay, and the Tasman regions.
This species was sold through the nursery trade for many years so there may still be plants tucked away in gardens or around ponds or waterways. Some of the plants sold through nurseries were variegated and have green and white striped leaves. Phragmites prefer the margins of water bodies, both freshwater and saline, but can also grow away from water.
Phragmites eradication programme
Phragmites is one of the species being eradicated through the National Interest Pest Responses programme. The eradication programme consists of containment of known infestations to prevent spread, site treatment (which can be manual removal of plants or herbicide application) and monitoring until eradication can be declared. Due to the longevity of the seed, a site is monitored until it has been clear of plant material for 10 consecutive years to ensure eradication. Phragmites has been successfully eradicated from multiple sites and are on track to eradicate this species from New Zealand.
Biosecurity New Zealand works closely with the regional councils and other organisations to eradicate this weed from New Zealand.
National Interest Pest Responses programme
What to do if you find phragmites
Phragmites is an Unwanted Organism under the Biosecurity Act (1993). Propagation, spread, display, and sale are all prohibited. It is also a Notifiable Organism, which means you must report all sightings to the Ministry for Primary Industries (MPI).
If you think you have found phragmites:
- freephone our pest and disease hotline on 0800 809 966
- don’t touch the plants or try to remove them
- take photos and leave the plants so they can be treated or removed safely without spreading them further.
What phragmites look like
