Groups of spartina form thick grassy clumps that spread through rhizomes (underground horizontal stems) or by overground side shoots. Spartina can establish in estuary environments (where there is a mix of fresh water and salt water), causing a build-up of sediment. This can alter the natural flushing cycles of the estuary habitat, increase the risk of flooding and change the habitat for wading birds and other estuary plants and animals.  

In Otago, scattered infestations occur in the Pleasant River estuary (between Waikouaiti and Palmerston), Karitāne estuary, Blueskin Bay, the lower Taieri River and Catlins Lake. 

• Size: Commonly grows up to one metre tall.
• Leaves: The leaves alternate sides of the stem and have wide, deep ribs on the upper surface and 1–3 millimetres ligules (membranes that attach the leaves to the stems). The leaves are 5–45 millimetres long by 4–15 millimetres wide. They are smooth to the touch in both directions, unlike other grasses, which feel rough in one direction.
• Seeds: There are several long, thick finger-like seed heads at the top of the stems. Seeds fall into the water and float away.
• Root system: Rhizomes and fibrous roots with erect stems (4–9 millimetres diameter).
• Similar species: In the intertidal zone (the area between high tide and low tide marks), there is one small native seagrass similar to spartina, Zostera, which can be differentiated by its thin, ribbon-like leaves that lie flat at low tide. Outside of the intertidal zone, other grass species similar to spartina include tall fescue and couch.
• Habitat: Shallow saltwater and freshwater environments, particularly estuaries.

During active growing season between November and March — in particular, when seed heads are visible.

To reduce the spread of spartina and minimise or prevent negative effects on economic wellbeing and the environment, everyone in Otago must report spartina infestations to Otago Regional Council. Spartina is in the progressive containment programme of the Otago Regional Pest Management Plan (2019–2029).  

Otago Regional Council carries out regular surveillance in places where spartina is known to be present and works closely with the Department of Conservation to control it. Together, these efforts aim to stop spartina spreading further and reduce its impact on local wetlands and estuaries.  

www.orc.govt.nz/spartina