What does it look like?
Pampas is a perennial, tussock-like grass. The two species (Cortaderia jubata and Cortaderia selloana) both have coarse abrasive leaves that are bluish green above and dark green below, with a noticeable midrib. Pampas grows 2-3m high and has flowering stems, which can be up to 5m high. Pampas have distinctive, erect, fluffy white or pinky-purple flower heads. Pampas may be confused with the three native toetoe species which have more creamy-yellow flower heads. The pampas species also have dead leaf bases which spiral, resembling wood shavings.
Pampas inhabits a range of areas including dunelands, plantation forests, quarries, roadsides and disturbed native forests. It will establish most easily in wet, sandy or bare soil and is tolerant of drought once established.
Why is it a problem?
Pampas plants are highly competitive and very invasive. Once seedlings are established, they can out compete native plants, forming dense and often impenetrable stands with weedy vines. Pampas quickly supresses the growth of other vegetation including groundcovers, shrubs and ferns. The rapid growth and accumulation of biomass above and below ground results in a domination of light, moisture and nutrient supply. In plantation forests, much of the fertiliser applied to trees is consumed by Pampas. Pampas also forms habitat for pests like rats, rabbits and possums which may have a detrimental impact on surrounding vegetation.
It produces flowering stems of up to 5m in the summer period from January to March (C. jubata), and in Autumn from March to May (C. selloana). Pampas produces a huge number of seeds (up to 100,000 with one plant able to produce millions of seeds over 10 - 15 years) that are predominantly dispersed by wind up to 50 kilometres. Seeds do not require fertilisation which means all seeds produced are viable and can result in the growth of a large number of seedlings.
Control methods
Physical control
Dig or grub out seedlings or small plants. Chainsaw small plants and remove sizeable plants by bulldozer. You can compost or leave on site to rot down. Burn or bury any flowerheads.
Herbicide control
Weed wipe (all year round) using glyphosate (200ml/L + penetrant). Or
Spray with Gallant (150ml/10l + crop oil) for most sites or glyphosate (100ml/10L + penetrant) for very dense sites. Use a marker dye to avoid wastage and a foaming agent to help prevent spray drift. Attack from multiple angles to ensure sufficient penetration into the clump. Leave the plants in the ground until the roots have died off.
Establish that the species is not the native toetoe (look for erect seed heads in autumn, toetoe droops) before attempting control.
CAUTION: When using any herbicide or pesticide, PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.
Related links
- https://apps.mpi.govt.nz/applications/nzpests-view/Article/621/PampasMinistry for Primary Industries
- https://www.nzpcn.org.nz/flora/species/cortaderia-selloana/
- https://www1.maf.govt.nz/uor-cgi/uor.pl/show?species_id=36652
- https://www1.maf.govt.nz/uor-cgi/uor.pl/show?species_id=36654
- https://www.weedbusters.org.nz/what-are-weeds/weed-list/pampas
- NPPA and the control of weeds | NZ Government
Management Programme
National Pest Plant Accord (NPPA)
The NPPA is designed to prevent the sale, distribution and propagation of a set list of pest plants (the Accord list) within New Zealand. If allowed to spread further, these pest plants could seriously damage the New Zealand economy and environment.
More informationUnwanted Organism
An unwanted organism is any organism that's capable of causing harm to natural or physical resources (like forests and waterways) or human health. A number of introduced pests in New Zealand are classed as unwanted.
Organism of Interest (OOI)
Organisms of Interest are those specified as pests under our Regional Pest Management Plan that are capable of causing significant adverse effects on one or several of our Regional values. These species warrant being watch-listed for ongoing surveillance or future control opportunities.
Taxonomies
FamilyPoaceae
TypePlants
GroupGrass
HabitatLand
Management ProgrammeNational Pest Plant Accord (NPPA)Unwanted OrganismOrganism of Interest (OOI)
