Nassella Tussock

(Stipa trichotoma)

Progressive Control Pest

Nassella Tussock is a tufted perennial plant, which when mature forms dense tussocks with A Nassella Tussock shrub. deep, fibrous roots. Fully grown tussocks usually grow up to 70 centimetres tall, with a leaf spread of up to 70 centimetres. Leaves are narrow, fibrous, drooping, rough and unpalatable. The plant can be distinguished from other tussocks by the whitish-green, densely packed and swollen leaf bases. The plant produces numerous, openly branched, slender stalks carrying seeds. Flowers and seeds are purplish, making Nassella Tussock easy to recognise during the flowering period (October to December). A mature plant can produce up to 120,000 seeds, which have a very long viability in the soil. Seeds can be spread by wind up to a kilometre from the parent plant. Seed dispersal can otherwise occur by water, animals, machinery, vehicles, agricultural produce, humans, and on the bark of harvested trees.

Reasons for the Strategy

Nassella Tussock is generally unpalatable to stock. It is well adapted to invade and smother other grassland species, thereby reducing stock carrying capacity. It is capable of invading moderate-and-low-producing pastures. The biological attributes of Nassella Tussock make it a real threat to pastoral land in the Tasman-Nelson region. The scale of the threat is demonstrated by severe infestations in other parts of the country, including Marlborough.

Nassella Tussock is assessed at “3” on the infestation curve. There are known sites of Nassella Tussock in the Richmond Hills, and in Cape Soucis. The low incidence of Nassella Tussock in the Tasman-Nelson region, extensive areas of suitable habitat, and the potential for it to cause significant adverse effects, mean the benefits of progressive control far outweigh the costs.


To reduce the distribution and density of Nassella Tussock in the Tasman-Nelson region during the term of the Strategy

Alternative Measures

The alternative option of “do nothing” or relying on voluntary control will not achieve the objective of reducing the distribution and density of Nassella Tussock, and will result in significant additional costs to the community through lost production and the increased cost of control in the future. Requiring total control is not practical. The long seed life of Nassella Tussock makes eradication extremely difficult, along with the difficulty of controlling it within forest plantations.

Strategy Rule for Nassella Tussock

The occupier:

  • shall destroy all adult and juvenile forms of Nassella Tussock on land that they occupy;
  • shall take all reasonable precautions to avoid its spread on animals, machinery, vehicles, agricultural produce, humans, and on the bark of harvested trees;
  • shall advise the Management Agency of any activity that may increase the risk of seed spread.

A breach of Strategy Rule 5.7.5 is an offence under Section 154(r) of the Biosecurity Act 1993.

Biosecurity Act Requirement

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