Pampas: common and purple (and cultivars)

Pampas can be confused with native toetoe species (Astroderia spp.). However, there are key differences between them. 

Austroderia fulvida, A. toetoe

Flower head

• Drooping flower heads (to 4 m tall) are creamy-yellow.
• Flowers October to January.

Fruit/seed

• Produces large fluffy seed heads (inflorescence) with numerous seeds.

Leaves/stems

• Tougher leaves and stems than pampas – livestock unlikely to eat it.
• White, waxy covering on leaf bases.
• Veins visible between the midrib and margin of leaves.
• Dead leaves droop but do not form wood shaving-like curls at the base of the clump.

Common and purple pampas are erect, tall, tussock-forming perennial grasses with razor-sharp leaf margins (hence the term ‘cutty grass’). They are a particular problem on roadsides (reducing visibility), along railways, in quarries and in newly planted forests. Infestations of both common and purple pampas are found throughout the Waikato region.

Both introduced pampas species (and their cultivars) are very invasive, and able to form dense impenetrable stands over 3 metres high. Their seed can be easily spread through wind-dispersal, and human-assisted dispersal, for example when it contaminates quarried materials. The ability of their numerous seeds to blanket areas with very rapid exclusive growth makes these plants a particular problem on any disturbed land, wetlands, coastal dune and cliff areas. Pampas inhibits the regeneration of native plant species and can outcompete young pines in plantation forests.

Pampas can also be a fire risk due to the large amount of dry matter it produces, and harbour pests such as rats, mice, rabbit, and possums.

Physical control

• Pampas can inflict nasty cuts, so wear gloves and protective clothing.
• For young plants, the best option is to loosen the soil and pull them out.
• For small infestations, cut the trunk or stems off as close to the ground as possible.
• A digger or bulldozer can be used to remove big plants.
• Physical control should be done before seeds form.
• Leaf matter can be left on site, acting as mulch and shading out the seed bank.

Herbicide control

Herbicides are most effective on pampas during spring and early summer while it is growing strongly. Spraying while the plants are flowering is less effective.

Cut stump treatment

• Plants can be slashed to about 30cm from the ground and the regrowth sprayed.
• Large mature clumps may require follow up control.

Spray application

• Very dense sites can be sprayed. Total coverage of the plant is required.

Safety when using herbicides

• Follow the instructions on the manufacturer’s label.
• Always wear protective clothing.
• Always minimise the risk to your other plants.
• Contact the supplier for further advice.

Summary of herbicides and application methods for control

Management

After initial control, it’s important to:

• clean out the site again at least annually to control regrowth
• stop weeds invading by replanting with non-pest plants (preferably native plants) once regrowth is no longer a problem