Pampas grass (Cortaderia species)

Pampass grass is a very large tussocky plant. It has become a weed in urban areas and coastal bushland.

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How does this weed affect you?

Pampas grass has become a major threat to national parks in and around Sydney and the Central Coast. Once established, the plant is very competitive, restricting the establishment of native trees, and can become a fire hazard and harbour vermin. Because of this, the Department of Environment and Climate Change has undertaken appropriate control programs in NSW.

Pampas grass is of greatest potential weed significance to forestry operations. However, it has not yet become a major problem in NSW forests.

Pampas grass is not considered an agricultural weed, because young plants are readily grazed by stock and it shows no ability to establish in cropping systems.

Where is it found?

In NSW pampas grass has mainly become naturalised in bushland on the Central Coast and in some areas of the Central Tablelands. In Sydney, it is considered a major environmental weed by many local councils and is subject to intensive control campaigns. Evidence suggests it is spreading quickly across land disturbed by coal mining to the west of Newcastle, with numerous small populations on the coastal plains of the north coast of NSW.

How does it spread?

Individual plants have the ability to produce vast quantities of windborne seed – up to 100,000 per flower head – which can infest areas within a 25 km radius. In many cases, garden plants are the seed source for infestations. Pampas grasses also have the ability to reproduce from rhizomes (underground stems).

Cortaderia selloana (common pampas grass), the most common species in NSW, is gynodioecious. That means there are separate female and hermaphrodite or bisexual plants. Both types vary slightly in their appearance. The female plants are prolific seeders if pollinated by a hermaphrodite plant.

It is commonly thought that many of the cultivated plants in Australia are female clones, and fail to produce seed because of the lack of hermaphrodite plants to pollinate them. This could be why pampas grass has failed to naturalise in many parts of Australia where only individual plants are cultivated.

Cortaderia jubata (pink pampas grass) plants are always female and apomictic. That is, they can reproduce without the need for fertilisation. It is important that this be taken into account if control programs are to be effective.

Established plants have a large root system up to 3.5m deep, and the tussock produces large quantities of flammable material. It is very competitive with other more desirable plants. It is the more aggressive species in NSW.

What does it look like?

Pampas grass is a robust, long-lived perennial plant. It generally takes the form of a large tussock, approximately 1–1.5 m across, with attractive, plumed flower heads carried on tall stems.

Table 1: Comparison of Cortaderia species.
 Common pampas
Cortaderia selloana
Pink pampas
Cortaderia jubata
*New Zealand pampas
Cortaderia richardii
Flower heads appear Mid-March to late May January to late March October to January
Flower head colour Generally white but can be pink or mauve Always pink when young, fading to dark brown Straw to gold
Height of tussock 2 metres 1.5–2 metres 2-3 metres
Height when in flower Up to 6 metres Up to 4 metres, held high above arching leaves Up to 5 metres
Leaves
  • Erect and arching towards tip
  • Margins finely serrated
  • Arching with leaf tips touching the ground
  • Margins finely serrated
  • Arching with tips touching the ground
  • Margins finely serrated
Leaf sheath
  • No distinctive midrib
  • Smooth to sparsely hairy
  • No distinctive midrib
  • Very hairy
  • Distinctive midrib
  • Covered with white-waxy bloom
* Cortaderia richardii is currently not present in NSW; however, early identification is critical for effective control.

Habitat

Pampas grass appears to have no particular habitat preference, and is found in a wide range of ecosystems. It prefers open, sunny conditions, but also does particularly well in wetter conditions, making mangrove areas along rivers and inlets and wet, disturbed heathlands especially vulnerable to infestation.

Common sites of infestation are roadsides, road cuttings, quarry faces, sand dunes, mine spoil, new forest plantations and burnt and mechanically disturbed bushland. It can thrive in low-fertility situations and also tolerate waterlogged conditions.

References

Dellow J and McCaffery A (2009). Pampass grass Primefact 697. NSW DPI, Orange. 

References

  • Dellow, J. and McCaffery, A. (2003) Pampas Grass. Agfact P7.6.40. NSW DPI, Orange.
  • Parsons, W.T. and Cuthbertson, E.G. (1992) Noxious Weeds of Australia, 2nd ed. CSIRO publishing.

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Control

The method of control for pampas grass depends on the site on which it occurs and the potential risk for causing new infestations. Permanent mechanical removal is recommended wherever possible.Mechanical removal of plants (permanent removal, used in high-risk areas)

Grubbing of plants, particularly when small, is the best method of control in urban and bushland areas. This can be difficult with large plants because of their extensive root system and the abrasive nature of the leaves.

Control of large plants is easier and more effective if any seed heads are removed first and the plant is slashed before grubbing the crown and roots. Seed heads should be placed in a plastic bag and destroyed in an appropriate way.

The best conditions for grubbing are when the soil is moist so removal is easier. The crown and roots must be completely removed from contact with the soil. Suitable disposal methods for plant material are necessary to prevent re-establishment.

Pampas grass is known to be an important summer egg-laying site for wildlife such as the diamond python. Timing of control methods such as slashing should be considered to avoid the destruction of important habitats at critical times.

Use of herbicides (low-risk areas)

Smaller plants (less than 40cm) can be controlled using a wiper applicator with the recommended herbicide. For larger plants, slash the plant to reduce the foliage, taking care to dispose of any plant material in the appropriate way to prevent re-establishment, and then spray with the recommended herbicide.

Alternatively, the plant can be burnt (if local conditions allow), allowed to recover, and any new growth sprayed with the recommended herbicide.

Do not spray plants stressed by drought or frost, and ensure there is thorough wetting of larger plants with the herbicide. Follow-up treatment may be required if regrowth occurs. Prevention of seeding (temporary, used in low-risk areas).

Pampas grass is a prolific seeder. Its potential spread can be prevented by removing the flowering plumes before the pollen and seeds develop and are dispersed by the wind.

If removal is left until after the seed has developed, the seed head should be handled with care to prevent the seed shaking out. Any seed head containing viable seed should be burnt or rendered non-viable before discarding.

Grazing (temporary, used in low-risk areas)

Pampas grass is readily grazed by stock when it is young, before it becomes too abrasive. This prevents the development of flowers and seed set.

Herbicide options

WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au

See Using herbicides for more information.


Glyphosate 360 g/L (Roundup®)
Rate: 1.0 or 1.3 L per 100 L of water
Comments: Actively growing plants, before flowering, spring to autumn. Use higher rate on plants over 1 m high.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate


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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area Duty
All of NSW General Biosecurity Duty
All plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
Greater Sydney Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. Land managers should mitigate spread from their land. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
This Regional Recommended Measure applies to Cortaderia jubata (pink pampas grass)
Hunter
Exclusion zone: Upper Hunter local government area. Core infestation area: Port Stephens, Maitland, Cessnock, Lack Macquarie, Newcastle and MidCoast local government areas.
Regional Recommended Measure*
Whole region: The plant should not be bought, sold, grown, carried or released into the environment. Exclusion zone: The plant should be eradicated from the land and the land kept free of the plant. Land managers should mitigate the risk of the plant being introduced to their land. Core infestation area: Land managers should mitigate spread from their land.
North Coast Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
This Regional Recommended Measure applies to Cortaderia selloana and Cortaderia jubata (pink pampas grass)
South East Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
This Regional Recommended Measure applies to Cortaderia jubata (pink pampas grass)
*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfill the general biosecurity duty for this weed click here

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Reviewed 2017