Reed Sweet Grass

(Glyceria maxima)

Progressive Control Pest

Reed Sweet Grass is a tall grass on the edge of waterbodies growing up to 1.8 m tall with light green leaves up to 50cm long that may be upright or floating. The flowers are green, maturing to purplish-brown and carried on tall multibranched heads with numerous spikelets. It forms dense mats of rhizomes which produce vast numbers of shoots. A native of Europe and Asia, it has spread throughout the Waikato, the Hauraki Plains and parts of Otago.

Reasons for the Strategy

Reed sweet grass in a field.

Reed Sweet Grass can form dense impenetrable mats that impede access and drainage, causing silt accumulation and flooding. It replaces other aquatic margin vegetation and degrades habitat for aquatic fauna. It has been implicated in cyanide poisoning of livestock. It has the potential to take over wetland margins and the margins of other waterbodies and drains and represents a significant threat to wetlands and stock in the Tasman-Nelson region. It can be spread by seed or rhizome fragments in mud on machinery, footwear, livestock or in water. Most seed will germinate immediately but some will remain dormant for several years.

Reed Sweet Grass is tentatively assessed at “2” on the infestation curve. Given its limited distribution, the importance of remnant wetlands, and its potential impact on wetlands and stock, placing it into Progressive Control will provide benefits that outweigh the costs.


To reduce the distribution and density of Reed Sweet Grass in the Tasman-Nelson region during the term of the Strategy.

Alternative Measures

The option of “do nothing” or relying on voluntary control will not achieve the objective of reducing the density and distribution of Reed Sweet Grass, and could result in significant loss of indigenous biodiversity or loss of stock and increased costs of control in the future. Requiring total control is not considered appropriate at this time with limited information on its distribution.

Strategy Rule for Reed Sweet Grass

The occupier shall destroy all adult and juvenile forms of Reed Sweet Grass on land in the Tasman-Nelson region that they occupy.

A breach of Strategy Rule 5.x.5 is an offence under Section 154(r) of the Biosecurity Act 1993.

Biosecurity Act Requirement

No person shall knowingly sell, propagate, breed, release or display commercially, Reed Sweet Grass, under Sections 52 and 53 of the Act.